But some people say... no, they *demand* that human Mars landings must be perpetually banned not just because we may kill existing poor oppressed Martian bacteria with our evil racist white male supremacist Earth bacteria. No. Even if Mars has no life today, we must avoid landing because(wait for it)it may develop life many million years in the future!!!
Quote from: Stormbringer on 09/29/2015 11:39 amThere is probably going to be some serious resistance to doing this on biology and environmental grounds. Even basic terraforming activities could arguably destroy any remaining lifeforms or evidence thereof.What lifeforms?So far all we have evidence for that there are none. The biggest issue I would have with remaining martian life forms is the potential (unknown) hazard they could pose to people and equipment.
There is probably going to be some serious resistance to doing this on biology and environmental grounds. Even basic terraforming activities could arguably destroy any remaining lifeforms or evidence thereof.
I dunno- but it's not just radical environmentalist kookazoids stating objections like this. The space powers and organizations are trying to develop bio-security protocols to prevent contamination of places we land probes and eventually space ships on.
So I was just doing some browsing of Wikipedia and found the following:https://en.wikipedia.org/wiki/Halley%27s_Comet Halley's comet has a mass of 10^14 kg. Because it has a retrograde orbit, it passes Earth (and Mars) at about 71 km/s or 71 000 m/s.The mass of Mars' northern polar cap contains 1.6 million km^3 of ice (30% of which is CO2). https://en.wikipedia.org/wiki/MarsThis equates to 1.1 x 10^15 m^3 of ice, or (1.1 x 10^15 m^3)(1000 kg/m^3) = 1.1 x 10^18 kg of ice. To turn this into a liquid you would need (330 000 J/kg)(1.1 x 10^18 kg) = 3.6 x 10^23 J.The amount of CO2 if sublimed would be enough to make a 1 atm atmosphere:assume an atmosphere 10 000 m high, it would have a volume of 4(pi)(3.4 x 10^6 m^2)(10 000 m) = 1.5 x 10^17 m^3
Halley's comet has a mass of 10^14 kg. Because it has a retrograde orbit, it passes Earth (and Mars) at about 71 km/s
The impact of a large meteoroid can lead to the loss of atmosphere. If a collision is energetic enough, it is possible for ejecta, including atmospheric molecules, to reach escape velocity.
In extreme cases all the atmosphere above the tangent plane at point of impact is blasted away. As well as most of the cometary volatiles and some of the frozen volatiles at the impact site.
Quote from: Hop_David on 10/04/2015 08:21 pmIn extreme cases all the atmosphere above the tangent plane at point of impact is blasted away. As well as most of the cometary volatiles and some of the frozen volatiles at the impact site.Hmm, seeing that extinction level event asteroid impacts on earth have occurred rather frequently I have to wonder whether those had any impact on the density of earths atmosphere.
First Time Poster, Here:Crashing a few comets will not solve the basic Problem, for the following reasons.1) Mars orbit is too far from the sun to keep ANY portion of mars above Freezing point, even witha 1% CO2 in a 500 mb atmosphere. People forget how mild a Green House gas CO2 is. The onlytime the earth CO2 levels had an overwhelming impact was when it ended the great ice ball event. This was caused by the CO2 levels rising to 10%. and resulted in the end of the great glaciation event. Mars does not have a CO2 (Trapped in rocks or where ever) reservoir that large.2) while it would raise the MB levels to where water would flow, it would not last. The particulatesin the atmosphere will block the sun light, and initiate a global winter once the initial heat of the impact dissipates, and once again the atmosphere will freeze out. it would take a few years but that is a certainty.3) If you continually crashed smaller comets to keep the temperature up, the resulting global atmospheric shock wave would necessitate that any surface infrastructure would be destroyed.4) This would not solve the lack of magnetic field, and the surface while temporarily allowing some shirtsleeveoperations (with a respirator no doubt) you will still need to live underground in caves that are pressurized. If you had access to compact cheap portable energy source, then Titan would be a superior colonizationlocation. No radiation, Plenty of organics, easy access from surface to orbit (assuming you can get there)You would have to live in Ice Caves, but at least you could go outside with more modest protection, (using a heated inner suit, you could wear modest winter gear on the outside with a respirator. Try that on Mars.
First Time Poster, Here:Crashing a few comets will not solve the basic Problem, for the following reasons.1) Mars orbit is too far from the sun to keep ANY portion of mars above Freezing point, even witha 1% CO2 in a 500 mb atmosphere. People forget how mild a Green House gas CO2 is. The onlytime the earth CO2 levels had an overwhelming impact was when it ended the great ice ball event. This was caused by the CO2 levels rising to 10%. and resulted in the end of the great glaciation event. Mars does not have a CO2 (Trapped in rocks or where ever) reservoir that large.2) while it would raise the MB levels to where water would flow, it would not last. The particulatesin the atmosphere will block the sun light, and initiate a global winter once the initial heat of the impact dissipates, and once again the atmosphere will freeze out. it would take a few years but that is a certainty.3) If you continually crashed smaller comets to keep the temperature up, the resulting global atmospheric shock wave would necessitate that any surface infrastructure would be destroyed.4) This would not solve the lack of magnetic field, and the surface while temporarily allowing some shirtsleeveoperations (with a respirator no doubt) you will still need to live underground in caves that are pressurized. If you had access to compact cheap portable energy source, then Titan would be a superior colonizationlocation. No radiation, Plenty of organics, easy access from surface to orbit (assuming you can get there)You would have to live in Ice Caves, but at least you could go outside with more modest protection, (using a heated inner suit, you could wear modest winter gear on the outside with a respirator. Try that on Mars.[/quoteWelcome to the forum.As for your first point, It might be helpful if numbers for the total CO2 known to be on Mars were cited particularly the amount frozen at the poles.As for the second point-wouldn't a Mars with runningwater have rain that would wash particulates out of the atmosphere? As for small comets creating destructive global shock waves; it seems to me that the minimum size could be quite small since even those that burn up in the atmosphere add heating and gasses but ones that survive and make craters would still only need be a couple hundred feet in diameter particularly if the atmosphere is left at something like 4 psi and almost 100 percent CO2 for shirt sleeve pressure and liquid water. I doubt there would be any large area disturbance.On a warm shirt sleeve Mars you wouldn't have to live in ice caves but it might be quite a while before you can make it without supplemental oxygen.As for a magnetic field I remember a previous thread in which a superconducting wire at the equator was suggested.I think comet crashing makes Mars terra-forming relatively easy but I believe large tropical space colonies so large that they hold atmosphere without needing a roof will be what most humans live in in a couple centuries. Engineered inside out worlds with open sky and perfect climate sound nice to me but YMMV.As for Titan that would have to be some powerful energy source to warm that cold moon up wouldn't it?
Mars atmosphere is .6% that of earth. So if we were to totally heat up all the CO2, (hey by crashing a comet into it) , you would get somewhere around 2.5% of earth's atmosphere, and that atmosphere wouldconsist of 94% C02. the unfortunate facts are that mars has no buffering gas to increase it beyond this.
Quote from: Admiral_Ritt on 10/09/2015 02:50 am Mars atmosphere is .6% that of earth. So if we were to totally heat up all the CO2, (hey by crashing a comet into it) , you would get somewhere around 2.5% of earth's atmosphere, and that atmosphere wouldconsist of 94% C02. the unfortunate facts are that mars has no buffering gas to increase it beyond this. What about getting a buffering gas from the comet? Comets have ammonia, and let's not forget about ammonia combustion (the oxygen for which you could get from water on Mars) which yields N2:4 NH3 + 3 O2 → 2 N2 + 6 H2O (g)
You started off this thread suggesting we could "Quickly making an atmosphere on Mars by crashing a comet" into the planet. To provide Mars with 1atm pressure you'll need a comet, principally composed of the desired volatiles, with a mass of 3600,000,000,000,000 tonnes, if it's as dense as water it'll be 200km in diameter. There's no such object handy.
Haven't we established that there ain't enough CO2 in the caps?
Quote from: Alf Fass on 10/09/2015 04:33 amHaven't we established that there ain't enough CO2 in the caps?Fair enough. But I don't think we should abandon this comet crashing idea totally, because as some mentioned, you could get a runaway greenhouse effect with the CO2 you liberate, and if you crash more than one comet you could get a little more volatiles and heating.edit: don't forget: water is a greenhouse gas too!