Water Ice On Mars 364
cathector sends along a story from SpaceWeather.com on the discovery of water ice on Mars.
"Scientists have figured out the mysterious white substance unearthed by NASA's Phoenix lander on Mars. It's frozen water. The breakthrough came last week when Phoenix's stereo camera caught the substance in the act of disappearing. Bathed in martian sunlight for four days, the white substance sublimated — i.e., it transformed from solid to gas without passing through the liquid state. This is how water behaves on Mars.... Some readers have asked, how do we know the white substance is not frozen CO2 (dry ice) instead of frozen water? Answer: Phoenix's landing site is too warm for dry ice. The average daily temperature is about -70 F while dry ice requires temperatures lower than about -109 F." The animated GIF showing the ice sublimating is pretty nice too.
Wind? (Score:0, Interesting)
How do we know wind didn't blow stuff away?
Snow (Score:5, Interesting)
Water sublimating (Score:5, Interesting)
What about the pressure? (Score:2, Interesting)
And why are we using F? This is a science article, posted on a web site for nerds.
Re:Water sublimating (Score:5, Interesting)
Is water the only material that can sublimate? If not, why should we be so sure this has to be water just because we want it to be?
Re:Snow (Score:5, Interesting)
No, martian air is way too dry to form snow. There is water in the athmosphere, but IIRC it is something like a layer 1mm thick if all the water would condense on the ground. What happens is that some of that water freezes to/in the ground if it gets cold enough.
What I learned from following the press conferences online, is that since mars doesn't have a large moon, the axis of rotation changes much more than earth does, so if it is directed towards the sun, the ice could actually melt.
Re:Snow (Score:5, Interesting)
Re:Hundreds of millions spent and...? (Score:2, Interesting)
They haven't run the tests yet. This is just something they noticed when they landed.
We send this probe up there with all this fancy testing equipment, only to land in the friggin' stuff we're trying to find. It's actually pretty funny...
Re:Stupid terraforming.. (Score:3, Interesting)
Actually, that argument can be made for any atmospheric gas constituent, not just water vapor.
There is less water in the Martian atmosphere oxygen while the water is more massive, so the oxygen would leave at a proportionally greater rate (assuming we are observing a long term steady state). One theory of the rapid loss has more to do with disassociation of H and O by UV radiation. H would quickly leave by your molecular motion argument leaving a relatively larger amount of O.
If that's the case, we'd be much better off leaving it subsurface for life sustaining purposes - sublimed ice is lost water. Now, we could use a bunch of nukes to lift dust to the increase greenhouse effect ... :)
How come the water is so white/clean? (Score:5, Interesting)
First, I think the best evidence so far that this is water is not this picture, but the fact that the Mars Orbiter's spectrometer determined that that is was a lot of hydrogen in the ground near the poles.
That some white stuff vanishes is poor evidence. They need to get the white stuff in an oven and test it.
Let's assume it is water.
What really puzzles me is how clean the water is. It is covered with what would make a dirty mud if it ever melted together. Also on earth, you never have clean water if you have flash floods like what you see as a result of a volcanic eruption or meteroid impact. You only have clean water/ice in snow and still lakes/oceans.
This implies:
1. The ice has not melted after the dust blew over it.(A long time)
2. It used to be a lake/ocean or snow
So the purity of the ice might be a bigger discovery than the fact that it is ice there.
Re:Snow (Score:3, Interesting)
Re:ice on Mars is nothing new (Score:4, Interesting)
They are going at this the wrong way (Score:2, Interesting)
not necessarily amazing (Score:5, Interesting)
there's a number of geological processes that can concentrate water like this
in areas on earth where a lot of freezing and thawing occurs on earth, rocks get concentrated neatly in rings according to size, as if someone sorted them
i'm not saying this process is anything like why the ice is so pure on mars, what i am saying is that there are plenty of natural processes out there that concentrate materials in orders that, contraintuitively, seem like it took intelligent concentration, but are in fact totally natural
i won't even begin to speculate what processes on mars could do this, but i wouldn't be surprised if someone more knowledgeable than me could describe such a natural mechanism for ice purification on mars
Re:Wow - not (Score:2, Interesting)
Re:Water sublimating (Score:3, Interesting)
All materials sublimate
Not sure about helium. If it can sublimate then it's going to be way up the phase diagram at enormous pressure at or close to the critical temperature. But it can definitely go straight from the superfluid state to the vapour state.
It's quite bizarre when you watch He4 transition to superfluid as you reduce the pressure. It's boiling away vigourously and then suddenly all the boiling stops (and it becomes quite difficult to see because it's refractive index is so close to 1)
Tim.
Re:Um ...Dumb Question. (Score:3, Interesting)
Water freezes at zero degrees. :-p
But seriously, this is oversimplified. Water freezes at 0 degrees on Earth, at standard pressure. Furthermore, even when water freezes, there's still water vapor. Really, if you think about it, you can't have the physical states without multiple molecules. Liquids and solids require certain arrangements of multiple molecules. In either case, individual molecules can escape, thus sublimating. The energy from the sun was enough to cause these molecules to escape, even though the ambient temperature was below the melting point of water.
Really, the best way to think about the melting point and the boiling point is that the melting point is the lowest temperature at which liquid will exist, and the boiling point is the highest temperature at which liquid will exist. Gas can exist at all temperatures because gas is nothing more than molecules that have broken off from the liquid or solid.
Eventually, if you raise the temperature enough, no liquid or solid can form. Likewise, if you lower the temperature enough, eventually, no molecule can escape. This is why metal doesn't generally sublimate. The amount of energy needed is not provided by the temperatures commonly found on earth (metal can sublimate in other conditions).
Re:Wind? (Score:2, Interesting)
Re:Personally (Score:4, Interesting)
Re:How does the ice exist this close to the surfac (Score:2, Interesting)
If that -is- water in the white bands and not hardpan and a little seasonal frost, that might explain the darker areas within the streak - some localized melting in the sun.
It is true that the average daily high at this site at this point in time is -25*, but as anyone from northern States knows, surface temperature can be quite a bit higher than atmospheric temperature, and with the various salts we know are in the soil, the actual melting point can be below that daily average high. (Just as you have to walk through puddles to get to Stuffmart when it is that cold up here, because of all the salt they put down).
As to the probable frost in the soil, things like insulation from the sun (though at 1 inch depth, that wouldn't be much) tending the temp towards the daily average, isolation from the air (again, not much at that depth) and the added pressure of the soil bringing up the boiling point, could all be factors.
Personally, I don't think that they have ruled out that it -is- hardpan held together with either electrostatic force, or by a tiny amount of frost, which did then sublimate.
They say that Phoenix can't dig into the ice layer. Say -What-? Isn't that what they sent it to do? We really need to be willing to spend an extra 10 million per launch to use heavier lifters and more robust machinery! Very cost effective compared to what it costs to lighten and miniaturize things - just ask the Russians, they know this.
Re:Wow (Score:3, Interesting)
Does that make the robot less effective, or just slower?
Re:Wow (Score:3, Interesting)
Not necessarily - by not needing oxygen, and a way out, etc, it can prolong the stay. Maybe it can even more-than-compensate for its slowness.
So its not that clear-cut.