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.
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.
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.
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?
Quote from: Twark_Main on 01/11/2022 04:20 pmIf 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.
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?
Quote from: Roy_H on 06/03/2022 06:19 pmI'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.
...plants convert CO2 into carbon and oxygen, so maybe this could be done first?
Quote from: Slarty1080 on 06/06/2022 09:34 pmQuote from: Roy_H on 06/03/2022 06:19 pmI'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.
Quote from: Roy_H on 06/03/2022 06:19 pm...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?
Quote from: AU1.52 on 07/12/2022 10:48 pmHow 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.
Quote from: AU1.52 on 07/12/2022 10:48 pmHow 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.
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.
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."
