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............

jock & LongT

"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"

"The much lower pressure on Mars is below the triple points of both, so both sublimate."

So why do they think Mars had oceans? If what you both say is true would it not be impossible to have oceans of liquid water?

Just to make sure we're on the same page...

When ice sublimates, it goes directly to gas. It doesn't melt first, then go to gas. That would be evaporation.

==NASA states it is water ice==

However, their final judgment waits for the ovens to cook the stuff.

Quietman

I don't know much about the ocean hypothesis on Mars or who takes it seriously, but I think the idea is that it would have had a denser atmosphere, and therefore more pressure. Lose the atmosphere, lose the oceans.

I'm also not sure what the current pressure is relative to the triple point of water. I was just assuming based on what Ned reported.

what about dust falling and re-covering the "ice", from looking at the before and after on jpl's site that seems like a possibility to me as well to explain the disappearance. Exciting as it may be that it is ice, it seems a little premature for him to be making that announcement

Quietman; I'm not an authority by any stretch, but it's possible that Mars never has had any oceans. It's also possible that long ago, Mar's environment was different and could have had more of an atmosphere, but I think that because of it's smaller size, it's gravitational pull never did support much of an atmosphere that would allow a liquid water phase, so I think it unlikely. I think what is interesting now is that since it looks like water vapor and ice are there, where did the oxygen come from to make H2O? Also, there is apparently is some electrical atmospheric activity because I believe you also need that to bond hydrogen and oxygen.

Haven't we known for decades that water ice existed at the poles? I have been reading this for years. Orbiters can read the signature from space so not sure why anyone is acting surprised.

If Mars had all these oceans, where did all that water come from, and, if there was all this water, where are the clouds? Even over our poles, there are clouds.

Now, if we're talkin' carbon dioxide, where's all the vegetation???

If Mars had oceans, it had it long ago when it was young. Mars (and Earth) long ago had a lot more radioactive elements in their crust (i.e., as uranium decays, it releases heat). So a long time ago the interior was warmer and there were a lot more active volcanoes on the surface. Volcanoes release a lot of gas including water and carbon dioxide. So just on that basis, there was more gas in the atmosphere.

The problem with Mars is that it's smaller. So the planet both cooled quicker (less mass to hold heat + less radioactive elements = less volcanoes) AND its gravity is less than Earth. While Earth hangs onto its gas easily, Mars lost most of it to space and doesn't produce much either. We actually have support of this from Martian meteorites.

I really enjoy science and tech news stories, its a good relief from the same old political stories. I would really like ABC news to do more on this Mars rover and other stories like it.

I have to wonder about all the fuss about "water courses" on Mars. Could it possibly be that those supposed water flows can really be the result of volcanic activity, i.e., lava flows? I'm only asking, folks, not suggesting.

Mars DOES have thin whispy clouds. The Rovers have taken pictures of them. The "water courses" have been determined to be simple dry-dirt landslides.

==If Mars had oceans, it had it long ago when it was young.==

On Earth, all the water that ever was, is and every will be is here. That water has gone nowhere, only changed states. This is a rule of the universe.

If Mars had oceans, that water is still there. But where did it go, if it ever had any? It ought still be there, and such a hugh amount ought to be forming way more clouds from even ice crystals.

Now, there IS an atmosphere on Mars. Thin, maybe, but an atmosphere. It's enough to require a heat shield on an entry vehicle arriving from Earth, or someplace else. It's enough to be able to use a parachute; that's not possible in a very thin atmosphere.

A thin atmosphere's molecules are far apart. Such an atmopshere can hold a lotta water, IF there is a lotta water.

Here, in the Phoenix area, when it's hot, the molecules are very far apart, and, when moisture comes in from the Gulf of California in July through August, if it does in sufficient amounts, and that rising, hot air cools, the molecules get closer and they squeeze out the water, and that's what you see as huge, high, towering, cumulonimbuses, or is it "nimbi." But the atmosphere deoesn't make that water visible until it cools.

If Mars had oceans -- a lotta water -- it ought to be there in some form, and it must be getting into the atmosphere. Even though it's cool there, the molecules can't get close together enough to squeeze out that water. However, the atmosphere must be humid, in that case, and that can be measured, though not visible cuz it hasn't been squeezed out.

However, again, somewhere on that planet, it must be so cold that the molecules ARE closer together, and, if there's a lotta water there, they will squeeze out the water into visibility. But no. That's not happening on Mars. The only explanation is that the water isn't there.

If the water is there in ice form, and the atmosphere is thin, that frozen water is eager to get into the atmosphere [sublimation, not evaporation], and that ice should disappear very quickly. It doesn't. And, if it is getting into the atmosphere, there should be a lotta clouds. But, again, no.

BTW, there is enough of an atmosphere that it moves and makes significant dunes, significant erosions and significant other marks on the landscape.

Mr. Incredible -

I applaud your interest in working these things out, but some of your basic assumptions are misleading you:

1. Planets are not closed systems. Water vapor (or any other gas) can escape the atmosphere entirely and be lost to the system. This is what would have happened if atmospheric pressure was lost from an earlier period with oceans. At lower pressures, the water can simply boil off into space.

2. A thin atmosphere does not "leave room" for other molecules. A thin atmosphere means that gasses are not being held by the planet well, and this applies to ALL gasses more or less equally. In fact, the atmosphere on Mars holds about all the water vapor it can, which is why thin clouds often form around mountains.

3. Cold air tends to denser than warm air, because the molecules are less active. It is the kinetic energy (speed) of the molecules that determines the "temperature" more than does the density. It does not follow that dense air is always cold or thinner air is always warm.

==Cold air tends to denser than warm air, because the molecules are less active.==

It's not cuz they are not as active, rather that they are closer together.

The only reason you see moisture is that the air has cooled to a point where the moisture in the air has been squeezed out by the air molecules that are getting closer together. Cool air cannot hold as much water as warm air.

That's why condensation trails behind jets. The engines heat the air that has moisture in it [no visible moisture], and, as it cools behind the engine, the moisture becomes visible cuz the molecules in the cooler air are closer together than in the warmer air, and the same amount of moisture in the warmer air that is not visible, is visible in the cooler air.

Mr. Incredible - Condensation has nothing to do with water molecules being "squeezed out." The behavior of water vapor does not depend on the presence of other gasses in air. Condensation would occur at the dew point even if the only gas present is water vapor. It is dependent only on the kinetic energy of the molecules. There can be more water vapor in warmer air simply because the water molecules have more energy to evaporate.

jock
That makes sense. In winter the air is always drier than summer. At the lab in NJ it ran from 60% and up in summer but 40% and down in winter. But what effect is there from lower atmospheric pressure on Mars? Would it not be more like constant winter at Martian temps?

==Condensation has nothing to do with water molecules being "squeezed out."==

Actually, it does.

When the air is thin, as when it's hot, and there is water in the air, it is not visible.

In the southwest desert, it becomes visible when the hot air, mixed with invisible water, rises and cools. The faster it rises, the more threatening the cloud that forms.

== The behavior of water vapor does not depend on the presence of other gasses in air.==

It depends on how much water is in the air, the temperature of the air and how fast it rises into cooler air.

==Condensation would occur at the dew point even if the only gas present is water vapor.==

Not true of condensation. The water doesn't become visible until the air is cooled enough to squeeze it out. THAT's the dewpoint.

==It is dependent only on the kinetic energy of the molecules.==

No, it depends on the density of the air molecules.

==There can be more water vapor in warmer air simply because the water molecules have more energy to evaporate.==

Not true.

The water stays in the air, invisible, until the air is cooled, squeezing out thde water into the visible. Virga is an example where, in the cooler regions, the water is squeezed out of the air, falls, then, in the lower regions where the air can hold the water, goes back, or evaporates, into the air before it has a chance to hit the ground.

By the way, transonic vapor, formed on the wings of an airplane under certain circumstances, is an example of localized air pressure changes squeezing the water vapor out of the local air, causing it to become visible.

If Mars was a place on earth we would not want to live there or bother with the place. It is too cold, doesn't have air to breath and would be too expensive to use productively. But because Mars is so far away that makes it worth going to and exploring?? Its a miserable red cold God forsaken planet. Lets save our money and use it to do good here on this beautiful earth. Mars is where it is to balance our solar system - that's its function for us and we don't have to go there to make it perform that function.

"Mars’ northern hemisphere is an enormous lowland basin which might once have held a mighty ocean. The southern hemisphere comprises rugged, crater-pitted highlands with an altitude up to 8,000m (26,000ft) greater than the north. The new research suggests Mars bears the largest impact scar known anywhere in the Solar System."

from BBC News "Mars’ two-faced riddle ‘solved’ (6/28/08)"

This is all a wind up to get us to do a manned mission to Mars. A permanent base on the Moon makes sense. Sending people when robots work fine, make no sense.

If we are going to spend billions of dollars we should fiber all of America first. Kids in Wyoming, Vermont, and
ever rural New York will never get truly high speed Internet. We could then do bandwidth leases to companies who want to reach the masses.

Since Mars has no Magnetosphere the atmosphere slowly gets tore away by the solar wind. So at one point early on it could of had a very thick atmosphere and over the billions of years this is all that is left. As for the water I think its there kind of like rodents who were underground lived through the last E.L.E