NASA’s Retiring Top Scientist Says We Can Terraform Mars and Maybe Venus, Too

[su27k]

https://www.nytimes.com/2022/01/02/science/jim-green-nasa-mars.html

Since joining NASA in 1980, Jim Green has seen it all. He has helped the space agency understand Earth’s magnetic field, explore the outer solar system and search for life on Mars. As the new year arrived on Saturday, he bade farewell to the agency.

Over the past four decades, which includes 12 years as the director of NASA’s planetary science division and the last three years as its chief scientist, he has shaped much of NASA’s scientific inquiry, overseeing missions across the solar system and contributing to more than 100 scientific papers across a range of topics. While specializing in Earth’s magnetic field and plasma waves early in his career, he went on to diversify his research portfolio.

One of Dr. Green’s most recent significant proposals has been a scale for verifying the detection of alien life, called the “confidence of life detection,” or CoLD, scale. He has published work suggesting we could terraform Mars, or making it habitable for humans, using a giant magnetic shield to stop the sun from stripping the red planet’s atmosphere, raising the temperature on the surface. He has also long been a proponent of the exploration of other worlds, including a mission to Europa, the icy moon of Jupiter, that is scheduled to launch in 2024.

[Twark_Main]

He has published work suggesting we could terraform Mars, or making it habitable for humans, using a giant magnetic shield to stop the sun from stripping the red planet’s atmosphere, raising the temperature on the surface.

There's one data point which blows away this idea in anything except the extremely long-term (think "geologic time").

MAVEN has observed the Martian upper atmosphere for a full Martian year, and has determined the rate of loss of gas to space and the driving processes; 1–2 kg/s of gas are being lost.

So the maximum possible gain is 1-2 kg/s of atmosphere.

At this rate, 1% of the atmosphere would be conserved (not added, mind you) every 4-8 million years.

https://www.sciencedirect.com/science/article/abs/pii/S0019103517306917

[Robotbeat]

Yeah, I pointed that out to him. His defense is that he posits a super strong feedback mechanism so once you start reversing the process, the atmosphere will start to warm up and the surface will outgas quickly.

I don’t really buy it, though. I don’t buy the idea that there’s THAT strong of a feedback loop that you’ll get results in decades or centuries what ought to take tens of millions of years.

So you’ll need to provide the atmosphere and/or heat in some other way than indirectly through a magnetosphere. Giant mirrors should do the trick at least to the Armstrong Limit at low altitude and with enough mirrors (that you get off gassing even from tightly bound CO2 in rock and soil, not just CO2 ices, etc) something more comfortable than that. Also, delivery of gases from comets or icy bodies.

The upshot is you don’t even need a magnetosphere except in the extreme long term (millions to tens of millions of years), although annoyingly almost every single person on the Internet who knows anything about Mars at all is convinced you do since that is what every NOVA special or YouTube video about Mars says.

[spacenut]

Mars needs a magnetic field to keep from losing atmosphere, like our Van Allen belt.  This might be done with satellites, before they start terraforming.  Dirty industries on Mars could help heat up the atmosphere producing more CO2, heat and such. 

It seems like it would take a long time.  Much longer on Venus.

[Twark_Main]

If he thinks the Martian climate is that sensitive, yeeting 30 payloads of 100 tonnes of SF₆ each at Mars would achieve the same warming potential as 100 years of H₂ at 2 kg/s.

You wouldn't even need to send the Starship, just a disposable tank. Strap a Starlink to the tank for mid-course burns, keeping the Starship in Earth's SOI for immediate reuse. One Starship could launch many such payloads to Mars in one synodic period.


Of course I don't think the Martian climate is that sensitive to small warming "nudges," so IMHO this would be pointless. But if he believes it's true, why would he support an expensive mission (big magnet thing) over a cheap mission?

[Vultur]

Re sensitivity or not of the Martian climate system: I read years and years ago that Mars' axis tilt is thought to vary way more than Earth's (0 to 60 degrees or something) over hundreds of thousands of years, and at high tilt values, the CO2 ice at the poles probably sublimates.

Is that still thought to be true?

If so, doesn't that set a limit of how sensitive it can be if vaporizing all that CO2 doesn't turn it Earthlike?

[Slarty1080]

If he thinks the Martian climate is that sensitive, yeeting 30 payloads of 100 tonnes of SF₆ each at Mars would achieve the same warming potential as 100 years of H₂ at 2 kg/s.

You wouldn't even need to send the Starship, just a disposable tank. Strap a Starlink to the tank for mid-course burns, keeping the Starship in Earth's SOI for immediate reuse. One Starship could launch many such payloads to Mars in one synodic period.


Of course I don't think the Martian climate is that sensitive to small warming "nudges," so IMHO this would be pointless. But if he believes it's true, why would he support an expensive mission (big magnet thing) over a cheap mission?

Yes I take your point, although in practice can you imagine the reaction to any suggestion that 100 tonne payloads of SF₆ (23,000x more potent greenhouse gas than CO₂) being launched from Earth? If anything went wrong it would not be good on multiple levels.

[Twark_Main]

If he thinks the Martian climate is that sensitive, yeeting 30 payloads of 100 tonnes of SF₆ each at Mars would achieve the same warming potential as 100 years of H₂ at 2 kg/s.

You wouldn't even need to send the Starship, just a disposable tank. Strap a Starlink to the tank for mid-course burns, keeping the Starship in Earth's SOI for immediate reuse. One Starship could launch many such payloads to Mars in one synodic period.


Of course I don't think the Martian climate is that sensitive to small warming "nudges," so IMHO this would be pointless. But if he believes it's true, why would he support an expensive mission (big magnet thing) over a cheap mission?

Yes I take your point, although in practice can you imagine the reaction to any suggestion that 100 tonne payloads of SF₆ (23,000x more potent greenhouse gas than CO₂) being launched from Earth? If anything went wrong it would not be good on multiple levels.

People react in lots of silly ways, but the truth is that it would be a drop in the bucket compared to other SF6 emission sources.

Nike filled all their "Air" shoes from 1992 to 2006 with SF6, all of which eventually leaks out into the atmosphere. In the year 1997 alone they released 277 tons of the stuff.

[Roy_H]

I'm not going to argue that this proposal is practical from a cost/capability viewpoint, but more theoretical.

What if hundreds of large space craft were built designed to orbit between Saturn and Venus. On the low Saturn pass could they drop a long tube into the upper atmosphere and suck up thousands (millions?) of tons of Hydrogen (actually suck is the wrong term, pump at bottom of tube would be required) Then when low over Venus discharge this into the upper atmosphere, but igniting it so it will burn with oxygen and produce water for Venus. If these ships were totally automated maybe in a thousand years lakes and oceans would appear on Venus. Of course there are other major issues such as spinning up Venus and creating a protective magnetic shield like Earth. Venus does have the major advantage of being similar size to Earth. A method of cooling Venus could be huge Mylar reflective shield in orbit around Venus that would partially shade Venus.

Not much pure oxygen in Venus atmosphere, so the hydrogen would burn with Carbon Dioxide producing water and methane gas. Is there a method to get rid of the methane gas?

To answer my own question, plants convert CO₂ into carbon and oxygen, so maybe this could be done first?

[deadman1204]

Just because someone publishes something doesn't mean its true.

[Slarty1080]

I'm not going to argue that this proposal is practical from a cost/capability viewpoint, but more theoretical.

What if hundreds of large space craft were built designed to orbit between Saturn and Venus. On the low Saturn pass could they drop a long tube into the upper atmosphere and suck up thousands (millions?) of tons of Hydrogen (actually suck is the wrong term, pump at bottom of tube would be required) Then when low over Venus discharge this into the upper atmosphere, but igniting it so it will burn with oxygen and produce water for Venus. If these ships were totally automated maybe in a thousand years lakes and oceans would appear on Venus. Of course there are other major issues such as spinning up Venus and creating a protective magnetic shield like Earth. Venus does have the major advantage of being similar size to Earth. A method of cooling Venus could be huge Mylar reflective shield in orbit around Venus that would partially shade Venus.

Not much pure oxygen in Venus atmosphere, so the hydrogen would burn with Carbon Dioxide producing water and methane gas. Is there a method to get rid of the methane gas?

To answer my own question, plants convert CO₂ into carbon and oxygen, so maybe this could be done first?

I don't think this is even theoretically possible. Any ship passing by Saturn would have to be traveling in excess of Saturn's escape velocity (35km/s) else it would go into orbit. With a rotation of once every ten hours Saturn's cloud tops won't be moving at more than 10km/s so each tonne of gas extracted from Saturn would need to be supplied with an additional 25km/s of deltaV to leave Saturn. Its a total no starter even theoretically.

[Lampyridae]

I'm not going to argue that this proposal is practical from a cost/capability viewpoint, but more theoretical.

What if hundreds of large space craft were built designed to orbit between Saturn and Venus. On the low Saturn pass could they drop a long tube into the upper atmosphere and suck up thousands (millions?) of tons of Hydrogen (actually suck is the wrong term, pump at bottom of tube would be required) Then when low over Venus discharge this into the upper atmosphere, but igniting it so it will burn with oxygen and produce water for Venus. If these ships were totally automated maybe in a thousand years lakes and oceans would appear on Venus. Of course there are other major issues such as spinning up Venus and creating a protective magnetic shield like Earth. Venus does have the major advantage of being similar size to Earth. A method of cooling Venus could be huge Mylar reflective shield in orbit around Venus that would partially shade Venus.

Not much pure oxygen in Venus atmosphere, so the hydrogen would burn with Carbon Dioxide producing water and methane gas. Is there a method to get rid of the methane gas?

To answer my own question, plants convert CO₂ into carbon and oxygen, so maybe this could be done first?

I don't think this is even theoretically possible. Any ship passing by Saturn would have to be traveling in excess of Saturn's escape velocity (35km/s) else it would go into orbit. With a rotation of once every ten hours Saturn's cloud tops won't be moving at more than 10km/s so each tonne of gas extracted from Saturn would need to be supplied with an additional 25km/s of deltaV to leave Saturn. Its a total no starter even theoretically.

Chucking out the ship and its high approach velocity, it would be more feasible with Neptune or Uranus, especially since they have smaller gravity wells. Mine mass from the outer moons, and use that in a biiiig skyhook/tether to exchange momentum for the hydrogen. Obviously this is mega scale engineering with carbon nanotube strengths, cheap and easy fusion etc.

If you're really going to all that effort, rather give Callisto a magnetosphere and an atmosphere.

[JohnFornaro]

...plants convert CO2 into carbon and oxygen, so maybe this could be done first?

We're certainly not going to try that approach here on Earth, but it might be appropriate for Venus.

[Vahe231991]

I'm not going to argue that this proposal is practical from a cost/capability viewpoint, but more theoretical.

What if hundreds of large space craft were built designed to orbit between Saturn and Venus. On the low Saturn pass could they drop a long tube into the upper atmosphere and suck up thousands (millions?) of tons of Hydrogen (actually suck is the wrong term, pump at bottom of tube would be required) Then when low over Venus discharge this into the upper atmosphere, but igniting it so it will burn with oxygen and produce water for Venus. If these ships were totally automated maybe in a thousand years lakes and oceans would appear on Venus. Of course there are other major issues such as spinning up Venus and creating a protective magnetic shield like Earth. Venus does have the major advantage of being similar size to Earth. A method of cooling Venus could be huge Mylar reflective shield in orbit around Venus that would partially shade Venus.

Not much pure oxygen in Venus atmosphere, so the hydrogen would burn with Carbon Dioxide producing water and methane gas. Is there a method to get rid of the methane gas?

To answer my own question, plants convert CO₂ into carbon and oxygen, so maybe this could be done first?

I don't think this is even theoretically possible. Any ship passing by Saturn would have to be traveling in excess of Saturn's escape velocity (35km/s) else it would go into orbit. With a rotation of once every ten hours Saturn's cloud tops won't be moving at more than 10km/s so each tonne of gas extracted from Saturn would need to be supplied with an additional 25km/s of deltaV to leave Saturn. Its a total no starter even theoretically.

Chucking out the ship and its high approach velocity, it would be more feasible with Neptune or Uranus, especially since they have smaller gravity wells. Mine mass from the outer moons, and use that in a biiiig skyhook/tether to exchange momentum for the hydrogen. Obviously this is mega scale engineering with carbon nanotube strengths, cheap and easy fusion etc.

If you're really going to all that effort, rather give Callisto a magnetosphere and an atmosphere.

There was a study published in 2003 by Pat Troutman and Kristen Bethke suggesting that Callisto might be a suitable place for a human base for future exploration of the Jovian system due to its low radiation levels. However, terraforming Callisto would be an astronomically costly task.

Link:
https://web.archive.org/web/20120119170143/http://www.nasa-academy.org/soffen/travelgrant/bethke.pdf

[JulesVerneATV]

Venus, not so sure.

[AU1.52]

...plants convert CO2 into carbon and oxygen, so maybe this could be done first?

We're certainly not going to try that approach here on Earth, but it might be appropriate for Venus.

How would the plants with stand the surface pressure?

[VSECOTSPE]

How would the plants with stand the surface pressure?

Atmospheric algae, which is a thing here on Earth, high enough in the Venusian stratosphere to live in a 1 bar atmosphere.  Presumably genetically engineered to stay/reproduce quickly at that altitude and maximize CO2 extraction.  But algae require hydrogen to process CO2, which the Venusian atmosphere has largely lost to the solar wind due to its lack of magnetosphere.  So even with algae, you’re back to scooping and shipping ridiculous amounts of hydrogen from a gas giant in the outer solar system.

The (likely) more straightforward way to remove CO2 from the Venusian atmosphere is probably some form of solar shading combined with turning over its lithosphere (its surface rock) to expose its calcium and magnesium oxides.  The equilibrium at Venus between the surface oxides and the atmospheric CO2 is really unstable, and once exposed, the oxides will sequester a lot of CO2 in carbonates over a period of hundreds or thousands of years.  There are also catalysts that can to accelerate this process to under a century.  Turning over the lithosphere would probably involve some form of bombardment, and bombardment by meteoroids also rich in calcium and magnesium oxides would also accelerate the process.

That said, the stratosphere of Venus is the one natural location in the solar system that approximates Earth’s gravity and some measure of protection from cosmic radiation, i.e. aerostats in the Venusian atmosphere may be the one safe place besides Earth to live out a natural lifespan and have children.  (And you get a 1-bar atmosphere to boot.)  So we might not want to mess with it.

[Joffan]

How would the plants with stand the surface pressure?

Atmospheric algae, which is a thing here on Earth, high enough in the Venusian stratosphere to live in a 1 bar atmosphere.  Presumably genetically engineered to stay/reproduce quickly at that altitude and maximize CO2 extraction.  But algae require hydrogen to process CO2, which the Venusian atmosphere has largely lost to the solar wind due to its lack of magnetosphere.  So even with algae, you’re back to scooping and shipping ridiculous amounts of hydrogen from a gas giant in the outer solar system.

The (likely) more straightforward way to remove CO2 from the Venusian atmosphere is probably some form of solar shading combined with turning over its lithosphere (its surface rock) to expose its calcium and magnesium oxides.  The equilibrium at Venus between the surface oxides and the atmospheric CO2 is really unstable, and once exposed, the oxides will sequester a lot of CO2 in carbonates over a period of hundreds or thousands of years.  There are also catalysts that can to accelerate this process to under a century.  Turning over the lithosphere would probably involve some form of bombardment, and bombardment by meteoroids also rich in calcium and magnesium oxides would also accelerate the process.

That said, the stratosphere of Venus is the one natural location in the solar system that approximates Earth’s gravity and some measure of protection from cosmic radiation, i.e. aerostats in the Venusian atmosphere may be the one safe place besides Earth to live out a natural lifespan and have children.  (And you get a 1-bar atmosphere to boot.)  So we might not want to mess with it.

I'm a fan of setting up Venus bases in the clouds at the 50-ish km altitude sweet spot, and I don't think there is a serious risk of losing that desirable zone even if we start "improving" Venus. Reducing temperatures through locking up CO2 somehow could only result in the 1-atm zone changing altitude gradually, which a buoyant base would naturally follow without significant difficulty - maybe a little adjustment to buoyancy if the atmospheric composition moved a log way from the current mix..

[deadman1204]

How would the plants with stand the surface pressure?

The (likely) more straightforward way to remove CO2 from the Venusian atmosphere is probably some form of solar shading combined with turning over its lithosphere (its surface rock) to expose its calcium and magnesium oxides.  The equilibrium at Venus between the surface oxides and the atmospheric CO2 is really unstable, and once exposed, the oxides will sequester a lot of CO2 in carbonates over a period of hundreds or thousands of years.  There are also catalysts that can to accelerate this process to under a century.  Turning over the lithosphere would probably involve some form of bombardment, and bombardment by meteoroids also rich in calcium and magnesium oxides would also accelerate the process.

That said, the stratosphere of Venus is the one natural location in the solar system that approximates Earth’s gravity and some measure of protection from cosmic radiation, i.e. aerostats in the Venusian atmosphere may be the one safe place besides Earth to live out a natural lifespan and have children.  (And you get a 1-bar atmosphere to boot.)  So we might not want to mess with it.

Errrr, you really underestimate the size of a PLANET. Also time scales. It took hundreds of millions of years for all the oxygen sinks on earth to be exhausted (and oxygen is WAY more reactive than co2). "Turning over" the entire surface of a planet and letting it absorb all the co2 in a few hundred years? Thats beyond ludicrous.

Add a "catalyst"? So grind up the entire surface of a planet (I don't even have words for this...), and then mix it with another substance - JUST a few hundred trillion tons will do I'm sure...

To try and put terra forming into perspective, imagine moving the entire rocky mountain chain - from Canada to Mexico  to the moon. (Have you ever looked at how big a single mountain actually is?) Making our new lunar mountains would be incredibly easy compared to actually terraforming a planet, as it would involve moving a tiny amount of matter compared to the things you've suggested doing on Venus.

[VSECOTSPE]

It took hundreds of millions of years for all the oxygen sinks on earth to be exhausted (and oxygen is WAY more reactive than co2). "Turning over" the entire surface of a planet and letting it absorb all the co2 in a few hundred years? Thats beyond ludicrous.

Comes from research into carbon sequestration efforts on Earth, like this one:

Scientists have found a rapid way of producing magnesite, a mineral which stores carbon dioxide... A tonne of naturally-occurring magnesite can remove around half a tonne of CO2 from the atmosphere, but the rate of formation is very slow.

Project leader, Professor Ian Power (Trent University, Ontario, Canada) said:

"Our work shows two things. Firstly, we have explained how and how fast magnesite forms naturally. This is a process which takes hundreds to thousands of years in nature at Earth's surface. The second thing we have done is to demonstrate a pathway which speeds this process up dramatically"

The researchers were able to show that by using polystyrene microspheres as a catalyst, magnesite would form within 72 days. The microspheres themselves are unchanged by the production process, so they can ideally be reused.

"Using microspheres means that we were able to speed up magnesite formation by orders of magnitude. This process takes place at room temperature, meaning that magnesite production is extremely energy efficient"...

Commenting, Professor Peter Kelemen at Columbia University's Lamont Doherty Earth Observatory (New York) said "It is really exciting that this group has worked out the mechanism of natural magnesite crystallization at low temperatures, as has been previously observed—but not explained—in weathering of ultramafic rocks. The potential for accelerating the process is also important, potentially offering a benign and relatively inexpensive route to carbon storage, and perhaps even direct CO2 removal from air."

https://phys.org/news/2018-08-scientists-mineral-co2-atmosphere.html

To be clear, any terraforming is engineering on a crazy scale.  But there’s more crazy and there’s less crazy.  My two cents is that mining enough hydrogen from a gas giant in the outer solar system to seed entire oceans and shipping it to the atmosphere of Venus is more crazy than bombarding Venus with inner solar system asteroids to activate the massive but unused geological CO2 sinks that exist just beneath its surface.  The fact that we are uncovering catalytic processes through carbon sequestration research that can accelerate the carbon sink process from thousands of years to tens of days makes it even more reasonable than the alternative.  I’m not claiming that this terraforming scheme will work.  I’m not claiming that any terraforming scheme is sensible.  I’m just groping through degrees of insanity and saying this scheme seems somewhat less insane than this other one.

In general, my belief is that terraforming schemes that can create a runaway effect by kicking a planet’s existing chemical or physical disequilibria downhill will probably work better, faster, and more affordably than more brute force methods.  But since we are talking about changing extremely large and complex systems on scales humanity has never purposefully attempted, I’m qualifying that as a belief, not an observation.  At some point, any conversation about terraforming methods becomes angels on the head of a pin.

[colbourne]

Building a large sunshield between the Sun and Venus would eventually freeze out the atmosphere. It might be easier to do than some of the other suggestions here.

In the short term a base in the clouds seems something we could do without too much trouble and cost.

[JoeFromRIUSA]

Why not wait till the sun starts expanding and things will take care of themselves? (At least in Mars' case.  Heavy sarcasm. I mean in due time, Europa and Titan will be habitable, right"?

[daedalus1]

In the short term a base in the clouds seems something we could do without too much trouble and cost.

That is by far the biggest understatement I've probably ever seen.
Only a handful of countries have mastered the art of escaping the earth's surface with all the resources within fairly easy reach. The gravity in Venus's clouds is only slightly less than the earth's surface, no resources at hand to build multi stage rockets and no firm ground to bolt them to. And I'm only just beginning.

[colbourne]

In the short term a base in the clouds seems something we could do without too much trouble and cost.

That is by far the biggest understatement I've probably ever seen.
Only a handful of countries have mastered the art of escaping the earth's surface with all the resources within fairly easy reach. The gravity in Venus's clouds is only slightly less than the earth's surface, no resources at hand to build multi stage rockets and no firm ground to bolt them to. And I'm only just beginning.

If this was going to be a one way mission, for people who want to live the rest of their lives on Venus or until technology makes return to Earth simpler, it would be possible to have one rocket (delta V is less than going to Mars) launch a habitat that was bouyant with breathable gases, but would allow suitably equipped crew to go outside with not much more than a rebreather and acid proof suit. Some resources could be extracted from the atmosphere. Much more energy available from solar than Mars, and plants could be grown in buoyant floating spheres. I think this could be much cheaper than going to Mars.

[daedalus1]

In the short term a base in the clouds seems something we could do without too much trouble and cost.

That is by far the biggest understatement I've probably ever seen.
Only a handful of countries have mastered the art of escaping the earth's surface with all the resources within fairly easy reach. The gravity in Venus's clouds is only slightly less than the earth's surface, no resources at hand to build multi stage rockets and no firm ground to bolt them to. And I'm only just beginning.

If this was going to be a one way mission, for people who want to live the rest of their lives on Venus or until technology makes return to Earth simpler, it would be possible to have one rocket (delta V is less than going to Mars) launch a habitat that was bouyant with breathable gases, but would allow suitably equipped crew to go outside with not much more than a rebreather and acid proof suit. Some resources could be extracted from the atmosphere. Much more energy available from solar than Mars, and plants could be grown in buoyant floating spheres. I think this could be much cheaper than going to Mars.

If you say it quick it's easy you don't have to think about it. Try building a floating habitat just above the earth's surface. Get back to me when you've done a prototype scale model, say 10 people, and keep it floating and supplied without taking anything from the earth's surface.

[spacenut]

It would be easier to build a giant O'Neil cylinder or Babylon 5 type city that to build a floating city on Venus.  A large space city could be in orbit around the moon or at one of the Lagrange points.  It could take some raw materials from the moon and water or methane from earth.  It could manufacture things that could be manufactured in zero G in the center, and people could live on the rotating sides.  Food could be grown there, etc.  Then there wouldn't be a gravity problem like living on the moon for people's health.  Same is true for a Martian orbital colony, especially for expectant mothers, childbirth, and raising young children. 

A floating orbital city at Venus would have to get all their supplies from Earth.  A long way to travel.  They might be able to get some CO2 from the Venus atmosphere for methane manufacturing for station keeping or such.  Water?  It would have to come from earth.  I just don't see this happening unless they get some type of sun shade built to lower the temperature of Venus to comfortable levels. 

Mars would be easier due to water being available.  It needs some radiation shielding and atmosphere building before people could go without spacesuits or carry oxygen around.  At least there you can use Martian materials to build underground habitats. 

[JayWee]

A floating orbital city at Venus would have to get all their supplies from Earth.  A long way to travel.

Wouldn't that be quite challenging too? To get from venusian floating city to space you need a two stage reusable rocket.

[spacenut]

A floating orbital city at Venus would have to get all their supplies from Earth.  A long way to travel.

Wouldn't that be quite challenging too? To get from venusian floating city to space you need a two stage reusable rocket.

Unless it is very high in the atmosphere.  Also, Venus' gravity is about 1 G. 

I would see the moon, Mars, Ceres, the moons of Jupiter and Saturn way before Venus. 

[colbourne]

In the short term a base in the clouds seems something we could do without too much trouble and cost.

That is by far the biggest understatement I've probably ever seen.
Only a handful of countries have mastered the art of escaping the earth's surface with all the resources within fairly easy reach. The gravity in Venus's clouds is only slightly less than the earth's surface, no resources at hand to build multi stage rockets and no firm ground to bolt them to. And I'm only just beginning.

If this was going to be a one way mission, for people who want to live the rest of their lives on Venus or until technology makes return to Earth simpler, it would be possible to have one rocket (delta V is less than going to Mars) launch a habitat that was bouyant with breathable gases, but would allow suitably equipped crew to go outside with not much more than a rebreather and acid proof suit. Some resources could be extracted from the atmosphere. Much more energy available from solar than Mars, and plants could be grown in buoyant floating spheres. I think this could be much cheaper than going to Mars.

If you say it quick it's easy you don't have to think about it. Try building a floating habitat just above the earth's surface. Get back to me when you've done a prototype scale model, say 10 people, and keep it floating and supplied without taking anything from the earth's surface.

You mean like the Zeppelins built over 100 years ago that successfully circumvented the world.
Plastics could be made from the gases that can be extracted from the atmosphere. Metals could potentially be extracted this way as well.

[daedalus1]

In the short term a base in the clouds seems something we could do without too much trouble and cost.

That is by far the biggest understatement I've probably ever seen.
Only a handful of countries have mastered the art of escaping the earth's surface with all the resources within fairly easy reach. The gravity in Venus's clouds is only slightly less than the earth's surface, no resources at hand to build multi stage rockets and no firm ground to bolt them to. And I'm only just beginning.

If this was going to be a one way mission, for people who want to live the rest of their lives on Venus or until technology makes return to Earth simpler, it would be possible to have one rocket (delta V is less than going to Mars) launch a habitat that was bouyant with breathable gases, but would allow suitably equipped crew to go outside with not much more than a rebreather and acid proof suit. Some resources could be extracted from the atmosphere. Much more energy available from solar than Mars, and plants could be grown in buoyant floating spheres. I think this could be much cheaper than going to Mars.

If you say it quick it's easy you don't have to think about it. Try building a floating habitat just above the earth's surface. Get back to me when you've done a prototype scale model, say 10 people, and keep it floating and supplied without taking anything from the earth's surface.

You mean like the Zeppelins built over 100 years ago that successfully circumvented the world.
Plastics could be made from the gases that can be extracted from the atmosphere. Metals could potentially be extracted this way as well.

No. They took all their resources from the surface of the earth, and didn't have to worry about an artificial atmosphere.
They also landed many times.

[Slarty1080]

In the short term a base in the clouds seems something we could do without too much trouble and cost.

That is by far the biggest understatement I've probably ever seen.
Only a handful of countries have mastered the art of escaping the earth's surface with all the resources within fairly easy reach. The gravity in Venus's clouds is only slightly less than the earth's surface, no resources at hand to build multi stage rockets and no firm ground to bolt them to. And I'm only just beginning.

If this was going to be a one way mission, for people who want to live the rest of their lives on Venus or until technology makes return to Earth simpler, it would be possible to have one rocket (delta V is less than going to Mars) launch a habitat that was bouyant with breathable gases, but would allow suitably equipped crew to go outside with not much more than a rebreather and acid proof suit. Some resources could be extracted from the atmosphere. Much more energy available from solar than Mars, and plants could be grown in buoyant floating spheres. I think this could be much cheaper than going to Mars.

If you say it quick it's easy you don't have to think about it. Try building a floating habitat just above the earth's surface. Get back to me when you've done a prototype scale model, say 10 people, and keep it floating and supplied without taking anything from the earth's surface.

You mean like the Zeppelins built over 100 years ago that successfully circumvented the world.
Plastics could be made from the gases that can be extracted from the atmosphere. Metals could potentially be extracted this way as well.

No. They took all their resources from the surface of the earth, and didn't have to worry about an artificial atmosphere.
They also landed many times.

I think its fair to say that a floating habitat on Venus is feasible in theory, but would be extremely challenging to build (to say the least). Future technological developments might make it easier but there are many very difficult issues to resolve.

[VSECOTSPE]

The point to habitats in the Venusian atmosphere is that they may be the only near-term location besides large rotating well shielded space stations where humans can safely reproduce and live out long, natural lifetimes.  1/3g at Mars and 1/6g at the Moon may not be safe for embryonic development, and living out lives away from cosmic radiation underground may not be viable either.  (We don’t live decades in caves or underwater habitats).

No doubt, resources will be more of an issue at Venus than at Mars or the Moon.  But that will be a secondary concern for long-term settlement if generations cannot safely reproduce and live in the latter environments.

FWIW…

[Robotbeat]

The point to habitats in the Venusian atmosphere is that they may be the only near-term location besides large rotating well shielded space stations where humans can safely reproduce and live out long, natural lifetimes.  …

“Natural” being maybe the key word there. There are a ridiculous number of other biomedical countermeasures that can solve this problem if 1/3rd gee isn’t enough all by itself.

Humans haven’t been “natural” since the invention of cooking and clothing.

[VSECOTSPE]

There are a ridiculous number of other biomedical countermeasures that can solve this problem if 1/3rd gee isn’t enough all by itself.

For all intents and purposes, there are no medical countermeasures for those radiation environments on those timescales.  Same goes for abnormalities induced by gestation in low-g environments.

[daedalus1]

There are a ridiculous number of other biomedical countermeasures that can solve this problem if 1/3rd gee isn’t enough all by itself.

For all intents and purposes, there are no medical countermeasures for those radiation environments on those timescales.  Same goes for abnormalities induced by gestation in low-g environments.

There is absolutely no place in the solar system outside earth that you can have an environment like earth without being enclosed in some sort of bio shell. All these things wherever they are will involve massive investment in construction and transport. Saying floating habitats on Venus is the 'easiest' is crazy. The night for example is more than 200 days, how do you power it? Radiation is not insignificant, no magnetic field. People who want to return to earth, seriously how? One of the draws for people to colonize will be the human urge to explore, so that rules out Venus also and space stations.
I could go on.

[zubenelgenubi]

The night for example is more than 200 days, how do you power it?

The cloud-level atmosphere super-rotates, at the equatorial &/or temperate latitudes the clouds make a full rotation in 4 days.

Radiation is not insignificant, no magnetic field.

The bulk of the atmosphere screens UV, X-ray, gamma rays, cosmic radiation, etc., as Earth’s atmosphere does.  Venus has an ionosphere and aurorae without an internally generated magnetosphere.

What is lacking is water vapor and free oxygen. But there is a lot of carbon dioxide to screen sterilizing radiation.

What I do not recall is the altitude where the atmosphere most closely approximates Earth STP (Standard Temperature and Pressure).

[Lampyridae]

The night for example is more than 200 days, how do you power it?

The cloud-level atmosphere super-rotates, at the equatorial &/or temperate latitudes the clouds make a full rotation in 4 days.

Radiation is not insignificant, no magnetic field.

The bulk of the atmosphere screens UV, X-ray, gamma rays, cosmic radiation, etc., as Earth’s atmosphere does.  Venus has an ionosphere and aurorae without an internally generated magnetosphere.

What is lacking is water vapor and free oxygen. But there is a lot of carbon dioxide to screen sterilizing radiation.

What I do not recall is the altitude where the atmospheric temperature most closely approximates Earth STP (Standard Temperature and Pressure).

It works out to about 50km. But it's kind of hot at that level still, so it could work out to be more like 52km.

The amount of H2O in the atmosphere, while small, is about a tenth the concentration of CO2 in our own. Since it's a lot easier to get water vapour out of a gas (ie, condensation), it's not going to be a showstopper unless you need lakes of the stuff.

Surface mining can probably be done in a kind of smash-and-grab way, dropping down a harvester and calling in a carryall before the heat gets to be too much.

[VSECOTSPE]

There is absolutely no place in the solar system outside earth that you can have an environment like earth without being enclosed in some sort of bio shell.

There are shells and then there are shells.  At the right altitude in the Venusian atmosphere, you don’t need a pressure suit or thermal management because the ambient pressure and temperature is similar to Earth environments.  You still need an oxygen supply and skin covering to protect from lengthy exposure to corrosive chemicals in the atmosphere.  But you wouldn’t have to wear a lunar suit like at the Moon or Mars.  More like something approaching a SCUBA suit.

All these things wherever they are will involve massive investment in construction and transport.

Of course.  But with 0.9g and protection from cosmic radiation, the Venusian troposphere poses a lot fewer long-term health risks than other locations like the Moon and Mars.  If you want to bear healthy children and have them reach middle age without cancer and without living decades underground, the Earth and the Venusian stratosphere may be the only two naturally occurring environments in the solar system where that can be done.

I’m not saying it will make economic sense.  I’m not saying that a lot of people would want to live on Venusian aerostats.  I’m just saying that if the goal is true, long-term, multi-generational settlement, the Venusian troposphere may be the only naturally occurring environment off Earth where that can happen.

The night for example is more than 200 days, how do you power it?

We’re talking about aerostats in the Venusian atmosphere.  They’ll circle that globe once or twice per Earth week.  We’re not talking about surface habitats, where the thick cloud cover would probably make solar impractical (forget the night).

And there’s always nuclear, in any case.

Radiation is not insignificant, no magnetic field.

The thick Venusian atmosphere grants much greater protection from space radiation than at Mars or the Moon.

People who want to return to earth, seriously how?

NASA Langley’s HAVOC human Venus atmosphere exploration mission study baselined an air-launched, two-stage, LOX/methane ascent vehicle.  The methane could be produced from the Venusian atmosphere.

https://www.researchgate.net/profile/Christopher-Jones-54/publication/299905943_High_Altitude_Venus_Operational_Concept_HAVOC_An_Exploration_Strategy_for_Venus/links/5c6388e492851c48a9cfc25b/High-Altitude-Venus-Operational-Concept-HAVOC-An-Exploration-Strategy-for-Venus.pdf?origin=publication_detail

One of the draws for people to colonize will be the human urge to explore, so that rules out Venus

See HAVOC study above.

[Lampyridae]

Venus has an interesting situation where there is a massive abundance of energy. In the cloudtops, you get almost as much light from underneath as you do from overhead, so pretty much any surface will be illuminated and can be covered with solar cells. The atmosphere itself might also be a source of power, beyond something like tethered high-altitude windmills. Temperature differences within the atmosphere (8K/km) might allow for some kind of massive, airborne version of OTEC.

At 1 bar, the only real places to be able to walk around the exterior of an aerostat without some kind of cooling is near the poles, at about 80 degrees latitude. Temperatures do actually drop during the night, though (and actually get kind of chilly at night despite the enormous greenhouse effect). So there's probably going to be quite a bit of weather going on, and perhaps condensation harvesting.

Though I think Venus aerostats really have their own thread in Advanced Concepts.

[JohnFornaro]

But since we are talking about changing extremely large and complex systems on scales humanity has never purposefully attempted, I’m qualifying that as a belief, not an observation. 

Points awarded for accurately differentiating beliefs from observations.

[Robotbeat]

There are a ridiculous number of other biomedical countermeasures that can solve this problem if 1/3rd gee isn’t enough all by itself.

For all intents and purposes, there are no medical countermeasures for those radiation environments on those timescales.  Same goes for abnormalities induced by gestation in low-g environments.

All that’s required for radiation is shielding the buildings people spend >90% of their time inside anyway even on Earth. And your claim about 1/3rd g being a showstopper are not supported by science, which makes no such hard claims, even before we talk about countermeasures.

[JohnFornaro]

1/3g at Mars and 1/6g at the Moon may not be safe for embryonic development,

FWIW…

This is one of the stronger points arguing in favor of constructing a ring station at EML-1; about 1K yard in radius, 1 rpm, 1 gee at the rim, with 1/3 and 1/6 gee inner rings.  We could safely study embryonic development, an issue which is key for the thriving of terrestrial life in other than one gee environments.

[JohnFornaro]

...  And your claim about 1/3rd g being a showstopper are not supported by science, which makes no such hard claims, even before we talk about countermeasures.

A cursory search just now does not provide the scientific "support" you mention.   And the term "hard claim" is unwarranted.

Link please?

In space, astronauts have to take regular exercise to counteract the negative effects that weightlessness has on bone and muscle strength. On earth, a foetus in the womb also exercises, using the resistance of the amniotic fluid to strengthen its bones and muscles. In space, the lack of gravity could affect the development of a foetuses’ bones, muscles and other organs during pregnancy. 

https://www.thenakedscientists.com/articles/questions/qotw-would-foetus-develop-differently-zero-gravity-conditions

[zubenelgenubi]

the Venusian stratosphere

Minor point.
The troposphere extends above the hypothesized aerostat altitude.  The tropopause abuts the mesosphere--no stratosphere for Venus.

[VSECOTSPE]

All that’s required for radiation is shielding the buildings people spend >90% of their time inside anyway even on Earth.

We don’t have a good handle on the right cosmic ray shielding (polyethylene?) for spacecraft on missions measured in a few years.  Outside of piling regolith on top of structures and turning them into caves, I don’t think anyone has really looked at this for multi-decade surface structures.  I’m skeptical many individuals will trade Earth’s environments for living in a lunar or Martian cave for 90% (probably more) of their life.  No one lives in caves or in underwater pressure vessels for 90% (or even months) of their life on Earth.

Doesn’t mean many individuals will trade Earth’s environments for Venusian aerostats, either.  But I would not trade the cornfields I grew up around, the woods and (small mountains) I now like to hike, and swimming at a beach with my children for a life in a lunar or Martian cave.  And I’m a space cadet.  Given that, my 2 cents is that we need to think beyond the trite sci-fi and terrestrial settlement box if we’re really serious about true, multi-generational space settlement.

And your claim about 1/3rd g being a showstopper are not supported by science, which makes no such hard claims, even before we talk about countermeasures.

We need a centrifuge or two in LEO and some actual Artemis experiment space and time to run more and better experiments at 1/6g and 1/3g.  But what we’ve seen so far from mammalian gestation and development experiments in low-g does not look promising at all, and there would be no countermeasures for uterine implantation failures, blastocyst folding defects, brain voids, and the like that low-g environments inflict.

[VSECOTSPE]

The troposphere extends above the hypothesized aerostat altitude.  The tropopause abuts the mesosphere--no stratosphere for Venus.

Thanks, Z.  Corrected above.

[RoadWithoutEnd]

This is one of the stronger points arguing in favor of constructing a ring station at EML-1; about 1K yard in radius, 1 rpm, 1 gee at the rim, with 1/3 and 1/6 gee inner rings.  We could safely study embryonic development, an issue which is key for the thriving of terrestrial life in other than one gee environments.

People will probably study the matter "informally" regardless of risk, and won't wait for NASA permission or scientific consensus about safety.  Settling another world is obviously unsafe, so the attitude they'd take to risk will most likely be just asking whether the risk is worthwhile to humanity as a whole.

It would be nice to have answers up front, so research like you mention would of course be valuable.  But it could be obviated pretty quickly by a relative handful of people doing what they please out of hope and altruistic ambition.

The whole concept of pioneering new environments is that willing people volunteer as raw material to inform the species by their experiences, most of which are typically negative and personally costly in early years.  With the aid of the Scientific Method, the value of that sacrifice is greatly magnified, but wouldn't avoid the necessity for it unless the findings were conclusively bad.

In case anyone is deluding themselves about what space settlement would entail, it will be a gruesome spectacle... but it will learn and adapt quickly, and human beings everywhere will benefit.

[colbourne]

All that’s required for radiation is shielding the buildings people spend >90% of their time inside anyway even on Earth.

We don’t have a good handle on the right cosmic ray shielding (polyethylene?) for spacecraft on missions measured in a few years.  Outside of piling regolith on top of structures and turning them into caves, I don’t think anyone has really looked at this for multi-decade surface structures.  I’m skeptical many individuals will trade Earth’s environments for living in a lunar or Martian cave for 90% (probably more) of their life.  No one lives in caves or in underwater pressure vessels for 90% (or even months) of their life on Earth.

Doesn’t mean many individuals will trade Earth’s environments for Venusian aerostats, either.  But I would not trade the cornfields I grew up around, the woods and (small mountains) I now like to hike, and swimming at a beach with my children for a life in a lunar or Martian cave.  And I’m a space cadet.  Given that, my 2 cents is that we need to think beyond the trite sci-fi and terrestrial settlement box if we’re really serious about true, multi-generational space settlement.

And your claim about 1/3rd g being a showstopper are not supported by science, which makes no such hard claims, even before we talk about countermeasures.

We need a centrifuge or two in LEO and some actual Artemis experiment space and time to run more and better experiments at 1/6g and 1/3g.  But what we’ve seen so far from mammalian gestation and development experiments in low-g does not look promising at all, and there would be no countermeasures for uterine implantation failures, blastocyst folding defects, brain voids, and the like that low-g environments inflict.

I think you are right that most people would not like to spend 90% of their lives in caves or aerostats, but maybe we should think of people at the end of their lives ie over 80. It would be satisfying to think that you had colonised another world and on Earth you would have  been too old for such an important adventure. It is much easier to accomplish if we do not need to worry about a return trip. Supply missions could happen at regular intervals.

[JohnFornaro]

People will probably study the matter "informally" regardless of risk...

The long time casual observer wonders at the "informal" studying which may have taken place on ISS?

[Robotbeat]

All that’s required for radiation is shielding the buildings people spend >90% of their time inside anyway even on Earth.

We don’t have a good handle on the right cosmic ray shielding (polyethylene?) for spacecraft on missions measured in a few years.  Outside of piling regolith on top of structures and turning them into caves, I don’t think anyone has really looked at this for multi-decade surface structures.  I’m skeptical many individuals will trade Earth’s environments for living in a lunar or Martian cave for 90% (probably more) of their life.  No one lives in caves or in underwater pressure vessels for 90% (or even months) of their life on Earth.

Doesn’t mean many individuals will trade Earth’s environments for Venusian aerostats, either.  But I would not trade the cornfields I grew up around, the woods and (small mountains) I now like to hike, and swimming at a beach with my children for a life in a lunar or Martian cave.  And I’m a space cadet.  Given that, my 2 cents is that we need to think beyond the trite sci-fi and terrestrial settlement box if we’re really serious about true, multi-generational space settlement.

And your claim about 1/3rd g being a showstopper are not supported by science, which makes no such hard claims, even before we talk about countermeasures.

We need a centrifuge or two in LEO and some actual Artemis experiment space and time to run more and better experiments at 1/6g and 1/3g.  But what we’ve seen so far from mammalian gestation and development experiments in low-g does not look promising at all, and there would be no countermeasures for uterine implantation failures, blastocyst folding defects, brain voids, and the like that low-g environments inflict.

On the contrary, radiation shielding is already fairly well known, it’s just a matter of mass reduction and optimization. Mars has abundant materials for radiation shielding. A meter or two of water on the roof (not that heavy, thanks to Mars’ lower gravity) will largely do the trick (multistory buildings will naturally have much lower radiation on the bottom floors, so there’s a big benefit to scale).

That not everyone will want to do it is true, but if just 0.1% do and we can get the cost low enough, that’s more than enough.

I’m from a northern state, and some places already have commercial building ground snow load requirements equal to the equivalent of just under one meter of water at Mars’ gravity. It’s not a big deal.

[Greg Hullender]

When I lived in Tokyo, I was surprised just how much of an artificial environment it was. For example, unless you go up a skyscraper, you never see the horizon. Your apartment is very small, and whenever you're outside, you're always in a crowd. But after a while, you get used to it, and people who grow up there are uncomfortable when it's *not* crowded. (Or so they claimed.)

Now that's still a long way from life in a nuclear submarine, which people can tolerate for months but probably not for years, but I do think a lunar or Martian colony designed to be somewhere between Tokyo and a submarine could be long-term tolerable.

Something that might help would be at least one large domed space designed to give the illusion of being outdoors. When Disney's Pirates of the Caribbean was new, I remember being amazed that one or more of the "rooms" created a perfect illusion that we were outside. It helped that it was twilight--trying to simulate broad daylight probably isn't feasible, but maybe it's not necessary either. Just a place where people can not feel trapped if they need to.

[VSECOTSPE]

On the contrary, radiation shielding is already fairly well known, it’s just a matter of mass reduction and optimization.

This is inaccurate at best.  Mass reduction/optimization is an issue for spacecraft.  It’s not an issue for structures on worlds with a small fraction of Earth’s gravity, which is what we’re actually talking about.  We’re also talking about cosmic radiation (high-energy nuclei, not photons), so spalling effects remain an issue regardless of material.  And no one has thought through the multi-decade/century issues associated with preventing degradation of and maintaining some these materials.

A meter or two of water on the roof (not that heavy, thanks to Mars’ lower gravity) will largely do the trick

No, it won’t.  Cosmic rays don’t only come from straight up.  You have bury a building or encase it in shielding.  It’s like living in caves, for decades.  It’s something humans don’t do, even in subterranean and underwater environments on Earth.

That not everyone will want to do it is true, but if just 0.1% do and we can get the cost low enough, that’s more than enough.

Handwavium.  There’s no evidence for this.  And the counterargument is that there’s probably 0.1% of the population that’s mentally unstable, poorly informed, and/or of low-enough intelligence to sign up for anything.  That doesn’t mean they’re right population to man a space mission or settle the most inhospitable environments humanity has ever tried to live in.

I’m from a northern state, and some places already have commercial building ground snow load requirements equal to the equivalent of just under one meter of water at Mars’ gravity. It’s not a big deal.

Again, structural loading on planets with only 1/6th to 1/3rd Earth gravity is not the issue.

[Robotbeat]

When I lived in Tokyo, I was surprised just how much of an artificial environment it was. For example, unless you go up a skyscraper, you never see the horizon. Your apartment is very small, and whenever you're outside, you're always in a crowd. But after a while, you get used to it, and people who grow up there are uncomfortable when it's *not* crowded. (Or so they claimed.)

Now that's still a long way from life in a nuclear submarine, which people can tolerate for months but probably not for years, but I do think a lunar or Martian colony designed to be somewhere between Tokyo and a submarine could be long-term tolerable.

Something that might help would be at least one large domed space designed to give the illusion of being outdoors. When Disney's Pirates of the Caribbean was new, I remember being amazed that one or more of the "rooms" created a perfect illusion that we were outside. It helped that it was twilight--trying to simulate broad daylight probably isn't feasible, but maybe it's not necessary either. Just a place where people can not feel trapped if they need to.

Yeah, in Minnesota, we have big shopping malls (Mall of America has full sized evergreen trees in its well-lit amusement park in the center) and zoos and other large indoor spaces that simulate the outdoors.

And people will be able to go outside, both in vehicles and on EVAs. The radiation dose on the surface is not that large, less than ISS according to MSL’s measurements (and yes, this includes the quality factor difference between cosmic rays and other effects… turns out ISS and MSL experience a nearly identical average quality factor). At MSL’s altitude, you can go outside up to 35 hours a week without exceeding terrestrial radiation worker limits if the rest of the time is well-shielded. That’s much more than the average American spends outdoors.

Most radiation on Mars DOES come from above, unlike on the Moon, because radiation coming from near the horizon will have to pass through a LOT more atmosphere.

Spallation effects included, we do understand radiation enough to properly shield from it, in spite of claims otherwise.

[Robotbeat]

I tire of claims that we don’t understand radiation or spalling effects or whatever. Yes, we do. Would it be nice to narrow the error bars? Of course. But we know how to calculate shielding requirements for any desired dose level on Mars. It’s pretty simple, there’s even a website you can run modeling tests yourself just to see: https://oltaris.nasa.gov/

(This graph only goes to 30g/cm^2. 30g/cm^2 of water is just 30cm, or about a foot of water. This is in free space, and yeah, it includes spalling effects.)

[VSECOTSPE]

When I lived in Tokyo, I was surprised just how much of an artificial environment it was. For example, unless you go up a skyscraper, you never see the horizon. Your apartment is very small, and whenever you're outside, you're always in a crowd. But after a while, you get used to it, and people who grow up there are uncomfortable when it's *not* crowded. (Or so they claimed.)

...

Something that might help would be at least one large domed space designed to give the illusion of being outdoors. When Disney's Pirates of the Caribbean was new, I remember being amazed that one or more of the "rooms" created a perfect illusion that we were outside. It helped that it was twilight--trying to simulate broad daylight probably isn't feasible, but maybe it's not necessary either. Just a place where people can not feel trapped if they need to.

I think this is true.  It doesn’t solve the gravity issue, but if we could create an underground, miniaturized Tokyo or a Disneyland on the Moon or Mars, that should be a livable, desirable environment for entire lifetimes.  But by the time we’re doing that, it may be easier to just build the same environments in orbit.  And up there, you can spin it up and live in Earth gravity, to boot.

Now that's still a long way from life in a nuclear submarine, which people can tolerate for months but probably not for years, but I do think a lunar or Martian colony designed to be somewhere between Tokyo and a submarine could be long-term tolerable.

I’d argue that for true settlement, the environment has to be more than tolerable.  It doesn’t have to be a cruise ship.  But the privations can’t be considerably worse in degree or type than what humanity has encountered living on various frontiers on Earth.  Even on Earth, humans don’t live out lives in caves, on the highest mountaintops, on the seafloor, in Antarctica, on oceanic oil drilling rigs, etc.  We visit all these places for various reasons (work, research, adventure), but no one bears and raises children there or lives out multi-decade lives there.  And at these places, you can still live in 1g, not develop cancer at a young age from radiation, walk outside without a space suit, and breathe the air.  If we have not settled these extreme environments on Earth, there’s little reason to believe we’d settle the much more extreme environments at the Moon and Mars.  In the Venusian troposphere at least you get 0.9g, 1 bar atmosphere, Earth-like temps, and protection from cosmic rays.  But maybe humans need a planetary surface and can’t live out their lives on even ginormous aerostats.  Maybe O’Neill was right, and without something approximating his stations, we won’t truly settle space, just visit.  (Or we’ll have to alter our bodies and probably identity as a species to adapt to these environments or wait thousands/millions of years for terraforming.)

[Robotbeat]

Even a very modest partial terraforming would increase atmospheric mass enough on Mars to drastically reduce radiation doses even below the low level they currently are. Increasing the mass of the atmosphere about 5 times is enough to barely get above the Armstrong Limit on the lowest points of Mars and would be equivalent to adding almost two meters of water shielding (spherical) to everything outside at Hellas Basin altitude, about 1 meter at the datum and somewhere in between at likely landing sites.

[Robotbeat]

We can live on Mars, in clouds of Venus, or floating in free space. In every case there will be huge habitats needed. I think Mars is the easiest place to start due to VASTLY more resources available and being much safer than free space. It’ll be easier and cheaper to build huge habitats there than anywhere else.

[DanClemmensen]

We can live on Mars, in clouds of Venus, or floating in free space. In every case there will be huge habitats needed. I think Mars is the easiest place to start due to VASTLY more resources available and being much safer than free space.

You forgot the Moon. Vast resources, a much shorter commute, and lower gravity but not free-fall.

[VSECOTSPE]

I tire of claims that we don’t understand radiation or spalling effects or whatever. Yes, we do.

No, we don’t.  That community is still arguing over different propagation models, cross sections, and approximations.  They don’t have long-term data.  What they have may be good enough to bound the risks for a few years round trip by professional astronauts to Mars and even that may be medically unethical.  It’s not what’s needed, by a long shot, to support settlement — living out decades and bearing children in these environments.

You keep hearing that because it’s true, not because it’s false.

[Robotbeat]

We can live on Mars, in clouds of Venus, or floating in free space. In every case there will be huge habitats needed. I think Mars is the easiest place to start due to VASTLY more resources available and being much safer than free space.

You forgot the Moon. Vast resources, a much shorter commute, and lower gravity but not free-fall.

The resources on the Moon are desiccated, pulverized volcanic rock (with maybe a little frost in deeply cryogenic permanently shadowed craters). No atmosphere means the *propulsive* delta-v required to get there is actually significantly higher than needed to get to Mars. Mars has an atmosphere which means unlimited amounts of CO2 to easily make oxygen (and CO fuel!) as has already been demonstrated on Mars by Perseverance. Mars has around 1-2% water content in most of its soil in likely landing sites, has large buried glaciers and we’ve even dug down and *seen* the water ice directly on Phoenix, plus a bunch of new impacts showing ice on orbital photos. We can also do powered flight (as has already been demonstrated). The atmosphere actually contains enough nitrogen and water vapor that it can be worth extracting directly, giving you all the main bulk ingredients for complex organic chemistry purely from the atmosphere. It has a history of flowing water and thus water-concentrated ore deposits (you can see gypsum veins, etc). The atmosphere was enough to cushion countless iron-nickel meteorites to a soft enough landing that they’re still in one big chunk and can be melted down or hot-worked into useful items. All the minerals needed for life are found in abundance, like on Earth.

You’re right the Moon has much lower round trip time. This is why Mars will probably not be a huge tourism destination ever, but the Moon may develop a sizable tourism industry (which is already partially funding Starship). But other than that, Mars has nearly every advantage over the Moon for settlement.

(And luckily we can do both.)

[Robotbeat]

I tire of claims that we don’t understand radiation or spalling effects or whatever. Yes, we do.

No, we don’t.  That community is still arguing over different propagation models, cross sections, and approximations.  They don’t have long-term data.  What they have may be good enough to bound the risks for a few years round trip by professional astronauts to Mars and even that may be medically unethical.  It’s not what’s needed, by a long shot, to support settlement — living out decades and bearing children in these environments.

You keep hearing that because it’s true, not because it’s false.

Error bars, not orders of magnitude. I’m in that community!

And we know how to get doses low enough that they’re lower than the natural doses of many places where families are raised on Earth. That is an absolute fact. This isn’t a mystery, and playing the “think of the children” card is a desperate attempt to win a losing argument.

Again, the only thing needed to reduce the dose to arbitrarily low levels for astronauts is mass.

[VSECOTSPE]

Increasing the mass of the atmosphere about 5 times is enough to barely get above the Armstrong Limit on the lowest points of Mars

Back of the envelope, this is what’s required — 100km-wide solar reflectors, thousand-megawatt power sources, and/or crashing a handful of very special asteroids/dead comets on the surface — to do that kind of minimal terraforming at Mars.  It’s within the realm of possibility, but it’s also unobtainium as far as current technology and spending goes.

In this paper we propose a mathematical model of the Martian CO2 system, and use it to produce analysis which clarifies the potential of positive feedback to accelerate planetary engineering efforts. It is shown that by taking advantage of the feedback, the requirements for planetary engineering can be reduced by about 2 orders of magnitude relative to previous estimates. We examine the potential of various schemes for producing the initial warming to drive the process, including the stationing of orbiting mirrors, the importation of natural volatiles with high greenhouse capacity from the outer solar system, and the production of artificial halocarbon greenhouse gases on the Martian surface through in-situ industry.

If the orbital mirror scheme is adopted, mirrors with dimension on the order or 100 km radius are required to vaporize the CO2 in the south polar cap. If manufactured of solar sail like material, such mirrors would have a mass on the order of 200,000 tonnes. If manufactured in space out of asteroidal or Martian moon material, about 120 MWe-years of energy would be needed to produce the required aluminum. This amount of power can be provided by near-term multi-megawatt nuclear power units, such as the 5 MWe modules now under consideration for NEP spacecraft.

Orbital transfer of very massive bodies from the outer solar system can be accomplished using nuclear thermal rocket engines using the asteroid's volatile material as propellant. Using major planets for gravity assists, the rocket ∆V required to move an outer solar system asteroid onto a collision trajectory with Mars can be as little as 300 m/s. If the asteroid is made of NH3, specific impulses of about 400 s can be attained, and as little as 10% of the asteroid will be required for propellant. Four 5000 MWt NTR engines would require a 10 year burn time to push a 10 billion tonne asteroid through a ∆V of 300 m/s. About 4 such objects would be sufficient to greenhouse Mars.

Greenhousing Mars via the manufacture of halocarbon gases on the planet's surface may well be the most practical option. Total surface power requirements to drive planetary warming using this method are calculated and found to be on the order of 1000 MWe, and the required times scale for climate and atmosphere modification is on the order of 50 years.

It is concluded that a drastic modification of Martian conditions can be achieved using 21st century technology. The Mars so produced will closely resemble the conditions existing on the primitive Mars. Humans operating on the surface of such a Mars would require breathing gear, but pressure suits would be unnecessary.

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.24.8928&rep=rep1&type=pdf

[Robotbeat]

Increasing the mass of the atmosphere about 5 times is enough to barely get above the Armstrong Limit on the lowest points of Mars

Back of the envelope, this is what’s required — 100km-wide solar reflectors, thousand-megawatt power sources, and/or crashing a handful of very special asteroids/dead comets on the surface — to do that kind of minimal terraforming at Mars.  It’s within the realm of possibility, but it’s also unobtainium as far as current technology and spending goes.

In this paper we propose a mathematical model of the Martian CO2 system, and use it to produce analysis which clarifies the potential of positive feedback to accelerate planetary engineering efforts. It is shown that by taking advantage of the feedback, the requirements for planetary engineering can be reduced by about 2 orders of magnitude relative to previous estimates. We examine the potential of various schemes for producing the initial warming to drive the process, including the stationing of orbiting mirrors, the importation of natural volatiles with high greenhouse capacity from the outer solar system, and the production of artificial halocarbon greenhouse gases on the Martian surface through in-situ industry.

If the orbital mirror scheme is adopted, mirrors with dimension on the order or 100 km radius are required to vaporize the CO2 in the south polar cap. If manufactured of solar sail like material, such mirrors would have a mass on the order of 200,000 tonnes. If manufactured in space out of asteroidal or Martian moon material, about 120 MWe-years of energy would be needed to produce the required aluminum. This amount of power can be provided by near-term multi-megawatt nuclear power units, such as the 5 MWe modules now under consideration for NEP spacecraft.

Orbital transfer of very massive bodies from the outer solar system can be accomplished using nuclear thermal rocket engines using the asteroid's volatile material as propellant. Using major planets for gravity assists, the rocket ∆V required to move an outer solar system asteroid onto a collision trajectory with Mars can be as little as 300 m/s. If the asteroid is made of NH3, specific impulses of about 400 s can be attained, and as little as 10% of the asteroid will be required for propellant. Four 5000 MWt NTR engines would require a 10 year burn time to push a 10 billion tonne asteroid through a ∆V of 300 m/s. About 4 such objects would be sufficient to greenhouse Mars.

Greenhousing Mars via the manufacture of halocarbon gases on the planet's surface may well be the most practical option. Total surface power requirements to drive planetary warming using this method are calculated and found to be on the order of 1000 MWe, and the required times scale for climate and atmosphere modification is on the order of 50 years.

It is concluded that a drastic modification of Martian conditions can be achieved using 21st century technology. The Mars so produced will closely resemble the conditions existing on the primitive Mars. Humans operating on the surface of such a Mars would require breathing gear, but pressure suits would be unnecessary.

https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.24.8928&rep=rep1&type=pdf

100km diameter reflectors is how you do it IMO. Can be built like solar sails, a micron or two thick, a gram or two per square meter, a tonne or three per square kilometer, about 30,000 tonnes for the equivalent area of a 100km square kilometer. Being solar-sail-like, they can launch themselves from LEO to Mars. You’ll need many such reflectors, but a 100km diameter one at 30,000 tonnes is only about 200 Starship flights. At $10m/flight (by no means a minimum), that’s just $2B in launch costs per 100km reflector, or about the price of one SLS. Or to do that full 200,000 tonnes, about $13 billion in launch costs, less than SLS’s development costs and around half of NASA’s budget for just a single year. Spacecraft hardware costs might be dominant, but we could cost-engineer the design to use less expensive materials (aluminized Mylar, for example, *is* mass-produced in roughly sufficient quantities for food packaging). So not unobtanium.

(Same tech can be used for solar shading of Earth, of course, although that only addresses half of the climate+CO2 problem.)

[VSECOTSPE]

Error bars, not orders of magnitude.

On what timescales?  Years or decades?

I’m in that community!

Great, then link us to your papers on your models for cosmic ray spallation propagation.

And we know how to get doses low enough that they’re lower than the natural doses of many places where families are raised on Earth.

Yes, by going subsurface or by burying the environment under enough material.  But human don’t live out decades in such environments on Earth.  We’re not moles or even mole-people.

This isn’t a mystery, and playing the “think of the children” card is a desperate attempt to win a losing argument.

Radiation damage is cumulative.  Youth are particularly vulnerable.  No one should have to explain that to you if you’re actually “in the field”.

Again, the only thing needed to reduce the dose to arbitrarily low levels for astronauts is mass.

I’m not talking about astronaut visits on the scale of years..  I’m talking about settlement on the scale of decades and centuries.

[VSECOTSPE]

You’ll need many such reflectors, but a 100km diameter one at 30,000 tonnes is only about 200 Starship flights.

Handwavium.  We could have free Star Trek teleporters to get the material to orbit, and we still don’t understand how lightweight, kilometer-long objects can be built and maintained in space.  Forget 100 kilometers.

https://www.scientificamerican.com/article/china-wants-to-build-a-mega-spaceship-thats-nearly-a-mile-long/

[JohnFornaro]

We can live on Mars, in clouds of Venus, or floating in free space. In every case there will be huge habitats needed. I think Mars is the easiest place to start due to VASTLY more resources available and being much safer than free space.

You forgot the Moon. Vast resources, a much shorter commute, and lower gravity but not free-fall.

The commute time is typically handwaved away, along with the idea that practice on the proximate celestial body would be good preparation for the distant celestial body.

Oh great.  Here come the gravitationalists!

[JohnFornaro]

You’re right the Moon has much lower round trip time. This is why Mars will probably not be a huge tourism destination ever, but the Moon may develop a sizable tourism industry (which is already partially funding Starship). But other than that, Mars has nearly every advantage over the Moon for settlement.

Three day commute handwaved away in favor of a 6 month commute.  I don't understand why the commute is thought not to be a problem.

[JohnFornaro]

Again, the only thing needed to reduce the dose to arbitrarily low levels for astronauts is mass.

As I'm fond of saying, mass is your friend.

[Robotbeat]

You’re right the Moon has much lower round trip time. This is why Mars will probably not be a huge tourism destination ever, but the Moon may develop a sizable tourism industry (which is already partially funding Starship). But other than that, Mars has nearly every advantage over the Moon for settlement.

Three day commute handwaved away in favor of a 6 month commute.  I don't understand why the commute is thought not to be a problem.

Because if you’re settling, it’s not a commute. (Also, 3 month transit is feasible, at least some years.)

It *is* a problem if you’re thinking of it like just a worksite or a tourist location, instead of a permanent home.

[Robotbeat]

We can live on Mars, in clouds of Venus, or floating in free space. In every case there will be huge habitats needed. I think Mars is the easiest place to start due to VASTLY more resources available and being much safer than free space.

You forgot the Moon. Vast resources, a much shorter commute, and lower gravity but not free-fall.

The commute time is typically handwaved away, along with the idea that practice on the proximate celestial body would be good preparation for the distant celestial body.

Oh great.  Here come the gravitationalists!

We’re getting the practice with Artemis, whether we need it or not. It’s probably true that NASA would not have been comfortable picking Starship to go straight to Mars.

[JohnFornaro]

You’re right the Moon has much lower round trip time. ... Mars has nearly every advantage over the Moon for settlement.

Three day commute handwaved away in favor of a 6 month commute.  I don't understand why the commute is thought not to be a problem.

Because if you’re settling, it’s not a commute. (Also, 3 month transit is feasible, at least some years.) It *is* a problem if you’re thinking of it like just a worksite or a tourist location, instead of a permanent home.

A permanent home, to me, implies having children.  There is surprisingly little info to be found on the topic of human pregnancy on Mars.

It is more likely that Mars will feature commuter traffic for many years before permanency is established.  It would be a more productive discussion to discuss the problems of colonization roughly in the order in which they need to transpire.

[Lampyridae]

This isn’t a mystery, and playing the “think of the children” card is a desperate attempt to win a losing argument.

Radiation damage is cumulative.  Youth are particularly vulnerable.  No one should have to explain that to you if you’re actually “in the field”.

There is a split between the "radiation damage is cumulative" crowd and the "low radiation is tolerable, even beneficial" (aka radiation hormesis. What is indisputable is that there is a difference between acute and fractionated doses. We have single cases of people accidentally being exposed to low levels of radiation over a very long time, and they survived until old age.

Unfortunately, most of our understanding of radiation damage on young people is from nuclear weapons, or, accidental exposure to radioactive materials, ie acute. Very young children are of course most at risk, but adolescent girls have a massive risk increase which only matches those of boys around 20. Later menarche has a protective effect.

We are mostly concerned with neutron radiation behind cosmic ray shielding.

Beyond 200g of medium-Z shielding (eg Earth's atmosphere, regolith), there is a spike in neutron counts from radiation spallation. Then it drops off. The neutron contribution to dose is always much higher because of its quality factor. So neutron radiation is the primary concern as to cosmic radiation behind shielding. The dose contribution at airliner altitude (40k feet/13km) is about 50% neutrons, 5% muons. Above this level is the Pfotzer maximum where neutron counts hit their highest (55–165g/cm^2 overhead thickness or 18km). At sea level, it's muons but their dose contribution is insignificant at this stage. Geomagnetic latitude is a major factor in cosmic radiation dose.

A single New York-Beijing flight racks up 0.1mSv, and of course a round trip is 0.2mSv. There are probably many young frequent fliers, and they would easily surpass the 1mSv annual public exposure dose. Aircrew are limited to 20mSv, though a cap of 5mSv is imposed.

Since there were limited neutron irradiation sources for biological experiments, there hasn't been a lot of recent research. But what is interesting is the differences in response to neutron irradiation by age: mice irradiated at > 500 days old had better survival than mice irradiated > 200 days old. So there is likely some protective biological response we don't understand yet for older organisms, maybe it causes cancer stem cells to become senescent. However, the 0.5Gy–2Gy levels are far above what we would consider for living behind radiation shielding anyway.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0231511

[JayWee]

Radiation damage is cumulative.  Youth are particularly vulnerable.  No one should have to explain that to you if you’re actually “in the field”.

Are you aware of Ramsar in Iran?
https://en.wikipedia.org/wiki/Ramsar,_Iran#Radioactivity

Ramsar's Talesh Mahalleh district is the most radioactive inhabited area known on Earth, due to nearby hot springs and building materials originating from them.[12] A combined population of 2,000 residents from this district and other high radiation neighborhoods receive an average radiation dose of 10 mSv per year, ten times more than the ICRP recommended limit for exposure to the public from artificial sources.[13] Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a, and the committed dose from radon was 72 mSv/a.[14] This unique case is over 80 times higher than the world average background radiation.

Early anecdotal evidence from local doctors and preliminary cytogenetic studies suggested that there may be no such harmful effect, and possibly even a radio-adaptive effect.

Studies ongoing.

[VSECOTSPE]

Are you aware of Ramsar in Iran?

Unfortunately not helpful for our purposes.  Ramsar has high radon concentrations, which is not the same thing as cosmic radiation.  The former has to be inhaled to cause cancer, specifically lung cancer, the only kind of cancer correlated with radon.  By dint of their high-energy/velocity, cosmic rays penetrate the human body, damage nuclei, and instigate all kinds of cancers and other cell mutations and defects without any inhalation or ingestion. 

This is where we’re at in understanding the health dangers of cosmic radiation:

Previous studies have shown the health risks from galactic cosmic ray exposure to astronauts include cancer, central nervous system effects, cataracts, circulatory diseases and acute radiation syndromes. Cosmic rays, such as iron and titanium atoms, heavily damage the cells they traverse because of their very high rates of ionization.

Conventional risk models used by NASA and others assume DNA damage and mutation are the cause of radiation cancers. This is based on studies at high doses where all cells are traversed by heavy ions one or more times within much shorter-time periods than will occur during space missions.

“Exploring Mars will require missions of 900 days or longer and includes more than one year in deep space where exposures to all energies of galactic cosmic ray heavy ions are unavoidable,” Cucinotta explained. “Current levels of radiation shielding would, at best, modestly decrease the exposure risks.”

In these new findings, a non-targeted effect model – where cancer risk arises in bystander cells close to heavily damaged cells – is shown to lead to a two-fold or more increase in cancer risk compared to the conventional risk model for a Mars mission.

“Galactic cosmic ray exposure can devastate a cell’s nucleus and cause mutations that can result in cancers,” Cucinotta explained. “We learned the damaged cells send signals to the surrounding, unaffected cells and likely modify the tissues’ microenvironments. Those signals seem to inspire the healthy cells to mutate, thereby causing additional tumors or cancers.”

Cucinotta said the findings show a tremendous need for additional studies focused on cosmic ray exposures to tissues that dominate human cancer risks, and that these should begin prior to long-term space missions outside the Earth’s geomagnetic sphere.

He also acknowledged the need to address a moral conundrum.

"Waving or increasing acceptable risk levels raises serious ethical flags, if the true nature of the risks are not sufficiently understood."

https://www.unlv.edu/news/release/study-collateral-damage-cosmic-rays-increases-cancer-risk-mars-astronauts

I’m not arguing whether it’s ethical to send a handful of professional astronauts into that environment for a few years.  But I am pointing out that if experts are having that argument over professional astronauts, then we are a very, very long way from understanding the implications of sending non-professionals and families into that environment for decades.

[Vahe231991]

If terraforming Venus were feasible, would Venus lose its ability to shine brightly like a star in the morning, given that Venus itself was alternately called Lucifer by the Romans in reference to Venus appearing in the form of a star in the morning (hence Venus being nicknamed the Rose Morning Star or Venus Rose)?

[libra]

Yes, by going subsurface or by burying the environment under enough material.  But human don’t live out decades in such environments on Earth.  We’re not moles or even mole-people.

Bouncing off this... I get that argument, but those enormous caves on the Moon (see my signature) with all that oxygen in the regolith... they are quite apealing.
We could have, not a base but a colony, right on Earth doorstep.
I wonder if we could bore artificial skylights in the lava tube ceilings, to get some sunlight down there ?

Found a paper where they compare lava tube sizes on Earth, Mars and Moon.
Largest Earth lava tube: 30 m diameter.
Largest Mars lava tube: 300 m.
Largest lunar lava tube: 3000 m.

[Slarty1080]

Yes, by going subsurface or by burying the environment under enough material.  But human don’t live out decades in such environments on Earth.  We’re not moles or even mole-people.

Bouncing off this... I get that argument, but those enormous caves on the Moon (see my signature) with all that oxygen in the regolith... they are quite apealing.
We could have, not a base but a colony, right on Earth doorstep.
I wonder if we could bore artificial skylights in the lava tube ceilings, to get some sunlight down there ?

Found a paper where they compare lava tube sizes on Earth, Mars and Moon.
Largest Earth lava tube: 30 m diameter.
Largest Mars lava tube: 300 m.
Largest lunar lava tube: 3000 m.

I fear that a colony in the true sense of the word will not be a practical proposition on the Moon due to the low gravity. We don't know for sure, but it's much closer to 0g than 1g and I would be seriously worried about embryological development as well as bone growth in children considering the effects seen in adult astronauts in terms of bone loss. This is also a concern on Mars although less so. Venus would seem a much better bet.

[VSECOTSPE]

those enormous caves on the Moon (see my signature) with all that oxygen in the regolith... they are quite apealing.
We could have, not a base but a colony, right on Earth doorstep.
I wonder if we could bore artificial skylights in the lava tube ceilings, to get some sunlight down there ?

Found a paper where they compare lava tube sizes on Earth, Mars and Moon.
Largest Earth lava tube: 30 m diameter.
Largest Mars lava tube: 300 m.
Largest lunar lava tube: 3000 m.

We should investigate the possibility.  But all we have is remote sensing data.  We need ground truth.  Until then, I’m skeptical there are tubes big enough, deep enough, stable enough, accessible enough, and in the right locations to be useful.  And that’s before the cost of turning these subsurface environments into something that doesn’t feel like living in a cave.  And then there’s the low gravity.  At that point, we may be better off cost- and health-wise building big rotating space stations.

But we should definitely investigate the possibility and obtain ground truth.

[zubenelgenubi]

Moderator: Off-topic thread trim.

[su27k]

https://twitter.com/MaxFagin/status/1583527411177508864

NASA's Jim Green presenting on the concept of an artificial magnetic field at Mars-Sun L1 as a way to shield Mars from solar wind and halt Mars' atmospheric loss, so it can be terraformed "naturally". This idea keeps coming up, but I wish it didn't. I think it's a bad idea 🧵


It's not that the idea doesn't work. Best I can tell, the underlying physics is sound, and a ~65 GW electromagnet at Mars-Sun L1 would indeed create a Mars sized magnetotail, reducing the loss of the atmosphere by a factor of ~1000 or more. That's not the problem.


The problem is that a 65 GW L1 shield is a misalocation of resources. 65 GW is ~one Germany. I believe a Martian civilization will have that much power to spare someday, but there will *always* be better ways to use that much power *if* terraforming is the goal.


Mars' atmospheric loss rate is only ~10 kg/day. Even if the loss rate goes up ~10,000x when the atmosphere is thickened, it still wouldn't be worth stopping; because applying that same 65 GW of direct heat to the regolith would liberate ~1,000,000 kg_CO2/day to the atmosphere.

*CORRECTION*

I types the atm loss rate as ~10 kg/day. Correct value is ~10 kg/*second*.

But I did type the correct number into the calculation, so the tweet is in error, not the math.


That 65 GW wouldn't be enough to terraform Mars on its own via direct CO2 liberation (still a ~100 million year process) but it would still be faster than the ~billion years it would take if we did stop the leak, and let Mars "naturally" replenish its atmosphere.


Mars is a leaky aircraft carrier that takes ~billion years to sink. We can either:

1) Throw a cup of water overboard every few years

2) Use a fleet of helicopters to carry the aircraft carrier everywhere so it never touches the ocean

Adding a magnetic field to L1 is solution 2

[Slarty1080]

https://twitter.com/MaxFagin/status/1583527411177508864

NASA's Jim Green presenting on the concept of an artificial magnetic field at Mars-Sun L1 as a way to shield Mars from solar wind and halt Mars' atmospheric loss, so it can be terraformed "naturally". This idea keeps coming up, but I wish it didn't. I think it's a bad idea 🧵


It's not that the idea doesn't work. Best I can tell, the underlying physics is sound, and a ~65 GW electromagnet at Mars-Sun L1 would indeed create a Mars sized magnetotail, reducing the loss of the atmosphere by a factor of ~1000 or more. That's not the problem.


The problem is that a 65 GW L1 shield is a misalocation of resources. 65 GW is ~one Germany. I believe a Martian civilization will have that much power to spare someday, but there will *always* be better ways to use that much power *if* terraforming is the goal.


Mars' atmospheric loss rate is only ~10 kg/day. Even if the loss rate goes up ~10,000x when the atmosphere is thickened, it still wouldn't be worth stopping; because applying that same 65 GW of direct heat to the regolith would liberate ~1,000,000 kg_CO2/day to the atmosphere.

*CORRECTION*

I types the atm loss rate as ~10 kg/day. Correct value is ~10 kg/*second*.

But I did type the correct number into the calculation, so the tweet is in error, not the math.


That 65 GW wouldn't be enough to terraform Mars on its own via direct CO2 liberation (still a ~100 million year process) but it would still be faster than the ~billion years it would take if we did stop the leak, and let Mars "naturally" replenish its atmosphere.


Mars is a leaky aircraft carrier that takes ~billion years to sink. We can either:

1) Throw a cup of water overboard every few years

2) Use a fleet of helicopters to carry the aircraft carrier everywhere so it never touches the ocean

Adding a magnetic field to L1 is solution 2

I suspect that the 1000 tonnes/day of extra CO₂ would be adsorbed back into the regolith and/or precipitate out again at the poles within a short period of time as the warmed gas radiated the excess heat into space.

[Twark_Main]

I suspect that the 1000 tonnes/day of extra CO₂ would be adsorbed back into the regolith and/or precipitate out again at the poles within a short period of time as the warmed gas radiated the excess heat into space.

Right.

They should have done the steady-state equilibrium calculation, not just the raw sublimation rate.

Interestingly enough, when you start to lay out that math, you realize that it strongly depends on the coldest part of Mars.

If there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO₂.

In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.

[LMT]

If there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO₂.

In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.

No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect:  e.g., the 8 m surface CO2 cap would add < 1 W/m2.

Also, exposed and redistributed polar water ice would have high albedo relative to regolith:  i.e., poor absorption of insolation energy.

[rakaydos]

If there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO₂.

In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.

No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect:  e.g., the 8 m surface CO2 cap would add < 1 W/m2.

Also, exposed and redistributed polar water ice would have high albedo relative to regolith:  i.e., poor absorption of insolation energy.

Why release the H2O, then? We're only interested in the CO2, and there's wildly differnt melting points. Aim for a point above the CO2 sublimation temperatue but not above the H2o sublimation temperature.

[LMT]

If there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO₂.

In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.

No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect:  e.g., the 8 m surface CO2 cap would add < 1 W/m2.

Also, exposed and redistributed polar water ice would have high albedo relative to regolith:  i.e., poor absorption of insolation energy.

Why release the H2O, then? We're only interested in the CO2, and there's wildly differnt melting points. Aim for a point above the CO2 sublimation temperatue but not above the H2o sublimation temperature.

Cap CO2 can't terraform.  Numbers don't add up, as above, not even with cap H2O added.  It's common knowledge; don't ignore it.

[rakaydos]

No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect:  e.g., the 8 m surface CO2 cap would add < 1 W/m2.

Can you link to the actual paper, instead of the abstract? The abstract does not make any claims as to the value of cap CO2.

[Twark_Main]

If there were (hypothetically) a 1,000 square mile rectangle on Mars that was colder than everywhere else, you actually only have to warm up that one area to alter the equilibrium concentration of CO₂.

In the real world, of course, this 'rectangle' corresponds to the Martian north and south poles. Polar heating strategies (eg with orbital mirrors) therefore provide a disproportionate terraforming effect vs. evenly heating the entire surface.

No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect"

That's not what I said. Please read more carefully.

I said the Mars polar caps behave in the way I describe, ie they act as the (level-setting) "cold traps" on Mars. This is true regardless of your CO₂ source (comet, geologic, etc).


I guess you were confused by the phrase "disproportionate terraforming effect"? The effect of heating on raising equilibrium CO₂ concentration (heaven forbid you specify why, apparently  ) is disproportionate in cold traps vs other regions. That's my point. That and only that.

Just because an effect is "disproportionate" doesn't mean it's sufficient for any particular purpose (eg full terraforming of Mars with no other tricks up your sleeve). The word indicates a quantitative statement has a well-defined meaning in physics and math.

Fortunately everything's cleared up now.

[Twark_Main]

The cold trap issue I raise isn't limited to just CO₂. For instance our old buddy sulfur hexafluoride has a boiling point of just -50 °C.

Does this mean that if we build factories pumping out SF₆ it will "rain out" over the poles? How do we  compute the "dew point" and "relative humidity" of SF₆ in Martian atmosphere?

[LMT]

No, releasing the permanent (southern) polar cap CO2 ice would give no significant "terraforming effect", or rather, greenhouse effect:  e.g., the 8 m surface CO2 cap would add < 1 W/m2.

Can you link to the actual paper, instead of the abstract? The abstract does not make any claims as to the value of cap CO2.

It's a simple comparison:  ratio of atmospheric mass vs. permanent CO2 cap mass.  Likewise, greenhouse effect.

[LMT]

...sulfur hexafluoride has a boiling point of just -50 °C.

Does this mean that if we build factories pumping out SF₆ it will "rain out" over the poles?

[LMT]

...polar caps... act as the (level-setting) "cold traps" on Mars.

Of course not.  CO2 freezes far from the caps.

"The temperature gets so low, you start freezing the atmosphere onto the surface," said Sylvain Piqueux of NASA's Jet Propulsion Laboratory... "Once you reach that temperature, you don't get colder, you just accumulate more frost. So even on the polar caps, the surface temperature isn't any colder than what these lower-latitude regions get to overnight."

[sanman]

Isaac Arthur on terraforming Venus

[Twark_Main]

...polar caps... act as the (level-setting) "cold traps" on Mars.

Of course not.  CO2 freezes far from the caps.

"The temperature gets so low, you start freezing the atmosphere onto the surface," said Sylvain Piqueux of NASA's Jet Propulsion Laboratory... "Once you reach that temperature, you don't get colder, you just accumulate more frost. So even on the polar caps, the surface temperature isn't any colder than what these lower-latitude regions get to overnight."

Of course!  I guess I forgot that lesson from Kindergarten... 

Obviously the only thing that changes is the "polar" part. It's still true that the cold traps (wherever they are) act as CO2 level-setting mechanism, so to raise the equilibrium CO2 level you can heat only the cold traps and not the entire surface.

Also your link is (of course) broken. Mirror: https://web.archive.org/web/20201024034157/https://mars.nasa.gov/news/frosty-cold-nights-year-round-on-mars-may-stir-dust/