Science and Society

This is NOT a sarcastic question: How can we be sure it is WATER ice, and not a frozen atmospheric gas? I sincerely hope it IS water ice, which would prove the existence of water on Mars, and perhaps indicate Mars was once "greener". I just hope they're correct about what they've seen.

A thermometer on Mars would show the temp well below zero and well below the temp at our poles, and, still, the ice on this planet is not melting cuz-a the sun. It is sublimating [water evaporates], but not that fast.

If it is sublimating, where are the clouds? There ought to be clouds. But no.

Instead of digging for water, why not measure the humidity cuz, if there is water there, it would sublimate [again, ice does not evaporate; in above freezing temps, it melts, THEN the water evaporates] into the atmosphere, and it ought to register as humidity.

So, I think they are getting carried away by their wishes.

Dry Ice

==Dry Ice==

That would be carbon dioxide. Whence is carbon dioxide on Mars?

I don't think we could have any idea of what's on Mars without really going there. There could be frozen things other than water . Other types of life may be able to live off of dirt for all we know.

Note from Ned--

You raise some appropriately skeptical questions. If I understand right, part of the reason for the Phoenix team's confidence now is that they've been pretty confident there was water ice before they began the mission. A spectrometer on the Mars Odyssey orbiter showed readings consistent with water in 2002.

"Dry ice" -- frozen carbon dioxide -- would not sublimate in nearly the same way at the temperatures at the landing site. Water ice would because the air pressure is very low. (The Martian polar caps are believed mostly to be CO2.)

That said, could they be wrong? You bet. But they say they don't think so.

Mr. Incredible - Mars doesn't have a proper magnetosphere to contain an atmosphere, thus clouds of water, or anything else really, would be lost or dispersed pretty much immediately. This is why atmospheric pressure is so low, and why water goes straight to vapor when exposed to the sun. It's also why a humidity reading would come up nil, that is unless, we somehow exposed all of the water on the planet to the sun to be vaporized immediately, ala Total Recall, but even so, that scenario is ridiculous since it would all probably be lost into space almost immediately...I'm still crossing my fingers for the discovery of an underground parasitic twin mutant leader of mars though...

==Mars doesn't have a proper magnetosphere to contain an atmosphere...==

So, you're not saying that Mars has NO atmosphere.

If Mars had no atmosphere, the sky would be black, not reflect the orange-red of the planet that we see in the atmosphere today.

Also, high in our atmosphere, the pressure is low, and, still, clouds gather.

CORRECTON

==Mars doesn't have a proper magnetosphere to contain an atmosphere...==

So, you're saying that Mars has NO atmosphere.

No Mr incredible, that's not what i'm saying, it has a very thin atmosphere, not "NO atmosphere". I suppose i spoke loosely. Any body that size would have an atmosphere, for the sheer power of its gravity at least. Mars just doesn't have an atmosphere anywhere near as dense as ours, and thusly, it doesn't have clouds like ours. A thin haze, yes, but not big billowy clouds. It has a weak, thin atmosphere that does not do well to contain water, as ours does.

Timing the sublimation would help in determining if the "clumps" are CO2 OR WATER? But, wouldn't Phoenix's on board spectrum analyzers do the job of discerning?

This is very exciting! When do we launch the mission that will begin construction of power plants on the surface? It's time to start pumping CO2 into the atmosphere so that any plants we may decide to put there will have a chance to survive and produce oxygen for us. The way we make power & pollute here hurts our planet, but on Mars, it actually makes it more habitable! Launch the factories!

Mr. Incredible -

Mars has a thin atmosphere, and it is almost pure CO2; hence the dry ice at the polar ice caps. I guess we just have to take their word for it that this stiff acts like water ice and not dry ice.

jock
1) If it mostly CO2 and CO2 is this powerful GHG, why isn't it warm?

2) Is the freeziing and boiling point of water very different on Mars?

I said Dry Ice because it evaporates at colder temperatures than water ics.

Mr. Incredible
Yes, carbon dioxide, ie. frozen condensation of Martian atmosphere. I don't think they landed near water.

Because of atmospheric pressures on Mars are much lower, the freezing point is higher and boiling point is lower. As a result, the liquid phase has a much smaller range than on earth. Consequently when ice on Mars is exposed to its atmosphere, it very quickly "sublimates" and goes rapidly through the liquid stage directly to a gas (water vapor). We are really lucky that earth provides such an ideal environment for water to be liquid. We probably would not be here. That's how I understand it. Any comments?

Quietman - Well, I assume that it IS warmer than it would be without the atmosphere, same as on Earth. But the atmosphere is very thin and it is a longer ways from the Sun, so their "warmer" is still pretty darn cold.

LongT - Yeah, that's how I remember it. Carbon dioxide has a much higher triple point than water. (The triple point is the combination of temperature and pressure where all 3 states could theoretically coexist.)

The pressure on the Earth is between the triple points of water and CO2, so water can be in a liquid phase and CO2 cannot; therefore CO2 sublimates when the temperature goes up ("dry ice"). The much lower pressure on Mars is below the triple points of both, so both sublimate.

Maybe they are like white chunky earthworms, and went back under the soil once exposed............