Play online chess!

From	Message
brigadecommander 22-Jun-25, 04:32	blue berry's apod.nasa.gov
lord_shiva 22-Jun-25, 17:56	Dirty Water Bath Fascinating origin. Mars had water. Probably lost through UV dissociation of atmospheric vapor where the hydrogen was subsequently driven off. Magnetic field loss from mantle solidification likely accelerated that process. Just guesswork—I should cross examine the Gemini Oracle. Gemini Oracle: Mars lost its water primarily due to a thinning atmosphere and subsequent evaporation and escape of water vapor into space. This process was driven by the loss of the planet's magnetic field, which exposed the atmosphere to the solar wind and ultraviolet radiation from the Sun. These factors broke down water molecules into hydrogen and oxygen, with the lighter hydrogen escaping into space. Damn. I bet my explanation is slightly better.
apatzer 22-Jun-25, 18:07	The Borealis impact is a safer bet.
apatzer 22-Jun-25, 18:08	And yes, I know current computer models suggest otherwise. I simply disagree.
bobspringett 22-Jun-25, 18:47	Thanks for the photo, Athena! Mars still has plenty of water. It's just locked up as ice, rather than being liquid or in the atmosphere. The idea that it has been lost by dissociation in the atmosphere doesn't acknowledge the fact that there is still plenty of water there even now, nor explain how it got into the atmosphere to be dissociated, sine the sun was weaker in earlier ages than it is now and Mars is frozen NOW. So the real question isn't "How did Mars lose its water?", but "How was Mars formerly warm enough for surface water to be present for extended periods?" My guess (and I acknowledge it is purely a guess!) is that the early atmosphere of Mars included significant methane and ammonia, two gasses that would not freeze out but are strong greenhouse agents. These could have kept Mars warm enough for a high CO2 partial pressure to boost the greenhouse, ensuring liquid water on the surface. But both methane and ammonia can be dissociated by sunlight, and were gradually lost to the point that the ancient greenhouse regime collapsed and the CO2 by itself was insufficiant to maintain stability when the sun was weaker, freezing Mars as it is today. There is a shade of irony there. Under current insolation rates, if somehow all of Mars' CO2 magically put into the atmosphere today, then the CO2 would be ample to maintain an atmosphere dense and warm enough to maintain both itself and surface oceans of water. The problem is that Mars is currently just on the wrong side of the CO2 temperature/pressure/insolation curve. But if the CO2 concentration got over the 'hump', it would be a stable runaway greenhouse situation under the hotter sun we have in this epoch. Thirty years ago Robert Zubrin actually proposed a way of achieving this artificially. www.users.globalnet.co.uk.
apatzer 22-Jun-25, 19:01	The pressure of an atmosphere keeps water from boiling away or being stripped away by the solar wind. Atmospheric pressure is key to keeping liquids on the surface and a magnet field is key to keeping an atmosphere from being stripped away.
lord_shiva 22-Jun-25, 19:13	Solar Insolation Gemini offers: Four billion years ago, the Sun was significantly cooler, with estimates suggesting it was 25-30% less luminous than it is today. This would have made the young Earth considerably colder, potentially making it a "frozen chunk of ice water" if not for other factors. End quote. What about waste heat from radioactive decay, or heat from mantle convection?
apatzer 22-Jun-25, 19:48	For Brigadecommander youtube.com
bobspringett 22-Jun-25, 20:18	Apatzer 19:01 <Atmospheric pressure is key to keeping liquids on the surface> This is true AT A GIVEN TEMPERATURE. But at ANY given temperature, the equilibrium vapour pressure is fixed. If the atmospheric pressure is low, the equilibrium vapour pressure is low. If the temperature is below the triple point, then the liquid phase is not possible even at very low atmospheric pressure. Then it becomes an equilibrium pressure between solid and gas phases. But either way, the equilibrium partial vapour pressure is limited by temperature, not the total atmospheric pressure. <magnet field is key to keeping an atmosphere from being stripped away.> Again true, but the stripping of atmosphere by the sun is a very slow process. It is even slower if the gas in question is only a fraction of total pressure. Mars has lost atmosphere for over four billion years, and it still has lots of water for these two reasons. The first is how slowly atmosphere is stripped, the second is that the temperature is so low that very little of that atmosphere is water. Pretty much nothing is left but CO2, because this is a rather heavy molecule and solar wind is not powerful enough, and it is bound too tightly to be easily dissociated. into more easily strippable oxygen. If Mars was warmed to terrestrial temperatures and oceans formed, the amount of water vapour in the Martian atmosphere would increase enormously; but even so, it would take around a billion years to strip all the water out of Mars. Too long for it to be a problem for human settlement.
bobspringett 22-Jun-25, 20:24	Shiva 19:13 Thank you, Gemini! But is Gemini aware that Early Earth had a very thick CO2 component in its atmosphere? Lots of ammonia and methane, too (which is why I posit the same for Mars). That kept things warmer despite the lower insolation. Mantle convection in itself only re-distributes heat, it doesn't create it. But Early Earth would have had considerably more radioactive decay heat, as well as gravitational compression heat and probably a fair contribution from infall, ranging from dust grains to asteroids. So yes, there were lots of heat sources other than the sun.

GameKnot: play chess online, chess clubs, monthly chess tournaments, Internet chess league, chess teams, online chess puzzles, free online chess games database and more.