Martian Water - New theories with surprising implication

clark · 2003-02-14 10:49:25

New theories with surprising implications

http://www.spaceref.com/news/viewpr.html?pid=10756

The Martian polar caps are almost entirely water ice
For future Martian astronauts, finding a plentiful water supply may be as simple as grabbing an ice pick and getting to work. California Institute of Technology planetary scientists studying new satellite imagery think that the Martian polar ice caps are made almost entirely of water ice-with just a smattering of frozen carbon dioxide, or "dry ice," at the surface.

Reporting in the February 14 issue of the journal Science, Caltech planetary science professor Andy Ingersoll and his graduate student, Shane Byrne, present evidence that the decades-old model of the polar caps being made of dry ice is in error. The model dates back to 1966, when the first Mars spacecraft determined that the Martian atmosphere was largely carbon dioxide.

Exposed Water Ice Discovered near the South Pole of Mars, Sceince

A Sublimation Model for Martian South Polar Ice Features, Science

Scientists at the time argued that the ice caps themselves were solid dry ice and that the caps regulate the atmospheric pressure by evaporation and condensation. Later observations by the Viking spacecraft showed that the north polar cap contained water ice underneath its dry ice covering, but experts continued to believe that the south polar cap was made of dry ice.

However, recent high-resolution and thermal images from the Mars Global Surveyor and Mars Odyssey, respectively, show that the old model could not be accurate. The high-resolution images show flat-floored, circular pits eight meters deep and 200 to 1,000 meters in diameter at the south polar cap, and an outward growth rate of about one to three meters per year. Further, new infrared measurements from the newly arrived Mars Odyssey show that the lower material heats up, as water ice is expected to do in the Martian summer, and that the polar cap is too warm to be dry ice.

Based on this evidence, Byrne (the lead author) and Ingersoll conclude that the pitted layer is dry ice, but the material below, which makes up the floors of the pits and the bulk of the polar cap, is water ice.

This shows that the south polar cap is actually similar to the north pole, which was determined, on the basis of Viking data, to lose its one-meter covering of dry ice each summer, exposing the water ice underneath. The new results show that the difference between the two poles is that the south pole dry-ice cover is slightly thicker-about eight meters-and does not disappear entirely during the summertime.

Although the results show that future astronauts may not be obliged to haul their own water to the Red Planet, the news is paradoxically negative for the visionary plans often voiced for "terraforming" Mars in the distant future, Ingersoll says.

"Mars has all these flood and river channels, so one theory is that the planet was once warm and wet," Ingersoll says, explaining that a large amount of carbon dioxide in the atmosphere is thought to be the logical way to have a "greenhouse effect" that captures enough solar energy for liquid water to exist.

"If you wanted to make Mars warm and wet again, you'd need carbon dioxide, but there isn't nearly enough if the polar caps are made of water," Ingersoll adds. "Of course, terraforming Mars is wild stuff and is way in the future; but even then, there's the question of whether you'd have more than a tiny fraction of the carbon dioxide you'd need."

This is because the total mass of dry ice is only a few percent of the atmosphere's mass and thus is a poor regulator of atmospheric pressure, since it gets "used up" during warmer climates. For example, when Mars's spin axis is tipped closer to its orbit plane, which is analogous to a warm interglacial period on Earth, the dry ice evaporates entirely, but the atmospheric pressure remains almost unchanged.

The findings present a new scientific mystery to those who thought they had a good idea of how the atmospheres of the inner planets compared to each other. Planetary scientists have assumed that Earth, Venus, and Mars are similar in the total carbon dioxide content, with Earth having most of its carbon dioxide locked up in marine carbonates and Venus's carbon dioxide being in the atmosphere and causing the runaway greenhouse effect. By contrast, the eight-meter layer on the south polar ice cap on Mars means the planet has only a small fraction of the carbon dioxide found on Earth and Venus.

The new findings further pose the question of how Mars could have been warm and wet to begin with. Working backward, one would assume that there was once a sufficient amount of carbon dioxide in the atmosphere to trap enough solar energy to warm the planet, but there's simply not enough carbon dioxide for this to clearly have been the case.

"There could be other explanations," Byrne says. "It could be that Mars was a cold, wet planet; or it could be that the subterranean plumbing would allow for liquid water to be sealed off underneath the surface."

In one such scenario, perhaps the water flowed underneath a layer of ice and formed the channels and other erosion features. Then, perhaps, the ice sublimated away, to be eventually redeposited at the poles.

At any rate, Ingersoll and Byrne say that finding the missing carbon dioxide, or accounting for its absence, is now a major goal of Mars research.

Phobos · 2003-02-15 18:22:28

I hope some new theory doesn't come along and trash the current thinking about the composition of the polar caps. We should send a rover there capable of taking cores to verify that the caps are mostly water. I'm thinking the best place for a first colony on Mars might be at the poles simply because there would be easy access to water there. Producing oxygen and drinking water would be no problem as well as fuel. It might also be a good place to look for life or fossils deep underground.

dicktice · 2003-02-16 09:47:34

Tunneling to reside under the ice, as well as "consuming" the melt-water, as I seem to remember was (still is?) done in Anarctica, would also shield first arrivals from ultraviolet, etc. radiation. Your suggestion is a bit different from my initial idea, of "tenting" over narrow canyon tributaries--admittedly a strategy for second or third arrivals. Good thinking!

dicktice · 2003-03-15 11:20:55

Just read in latest issue of Nature: Mars is "sopping" with water, underground.

Palomar · 2003-03-15 12:24:58

I'm thinking the best place for a first colony on Mars might be at the poles simply because there would be easy access to water there. Producing oxygen and drinking water would be no problem as well as fuel. It might also be a good place to look for life or fossils deep underground.

*I've had similar thoughts. However, wouldn't sunlight be at a minimum at the Marsian poles, like here on Earth? I'm afraid I'm not overly familiar with whatever axis tilt Mars has, as compared to Earth. The planet as a whole is, of course, so incredibly cold; would being close to a pole make much difference, in a worsening manner? I have to presume it would be much colder near the poles, similar to Earth. But, again, I'm curious as to how many less hours of daylight there would be near, say, the north pole of Mars as compared to the hours of daylight on average, near the equator. They'll need all the sunlight they can get, for the greenhouses...and keeping in mind also that the sun is just that much farther from Mars, and that Mars has a more ellipitical orbit, so when it's at aphelion combined with being near a pole...hmmmm. Could prove a bit tougher for explorers/settlers/colonists, no?

Just some rambling thoughts...

--Cindy

Byron · 2003-03-15 12:35:08

Well, if the landing is timed with the onset of the long Martian summer, you have virtually unlimited daylight...great for putting those solar panels up. You just wouldn't want to be there during the winter, as it'd be dark most of the time. Mars has a tilt of about 24 degrees, remarkably similar to that of earth, so it'd be very similar to summer in Antarctica, just colder.

One problem I see concering a polar mission is the extra delta-v needed to convert to a polar orbit and landing, but with the certainty of having unlimited water and solar power, I'm sure it'd be worth the extra expense. As for the low temps, it's so dang cold anyway, I don't think being in the polar region will make that much of a difference.

B

Palomar · 2003-03-15 12:46:45

*I did a quick looksie on Google, found this (includes degrees of axis tilt for Mars and Earth):

http://www.geocities.com/eliser73/page2.html

Palomar · 2003-03-15 12:59:50

One problem I see concering a polar mission is the extra delta-v needed to convert to a polar orbit and landing,

*It's always got to be something, right? <wink> Byron, please explain further? Why this additional effort to land near a pole? Thanks!

--Cindy

Byron · 2003-03-15 14:26:22

Don't really know the details, Cindy, just something I remembered reading a while back...I think it has to do with the orbital plane of the craft leaving Earth having to change to a different plane for a polar orbit.

It's all about numbers, physics and math....stuff you don't really care for..lol

B

dicktice · 2003-03-16 08:52:24

Excuse me for butting in...but polar orbit would be best on arrival, to survey the planet rotating beneath you, before committing to land. Launching without planetary rotation to assist reaching escape velocity from Mars's surface, with 1/3rd-gee, and all that available water-ice at the poles to produce fuel from, shouldn't present a problem either--seems to me.

Palomar · 2003-03-17 18:57:11

*I think I get it: It'll be harder to land near the poles than, say, near the equator of Mars because...watch a top spin, or a basketball spinning on a fingertip: The entire object moves, but the spinning of the areas at the axises of the object -- being smaller in area as compared to the equitorial area -- is subject to more force (or intensity -??) because of the compactness of area.

Am I on the right track with this? I woke up at 4:30 a.m. today with this thought in mind. I hope to god I'm somewhere on the right track...at that god-awful hour and all.

HAPPY 10TH WEDDING ANNIVERSARY TO MY HUSBAND AND I, 3/17/03!!!

--Cindy

dicktice · 2003-03-17 20:09:56

Aw shucks, Cindy--it's not so much of a problem to land on Mars, being so light due to 1/3rd of an Earth-gee. So, even without rotational assist, a same-size launcher could reach polar escape velocity (at right angles to the equator) with a lot less boost than on Earth, see? (And please keep your husband out of this.)

Josh Cryer · 2003-03-17 20:48:50

Happy 10th Cindy!

Palomar · 2003-03-17 21:52:34

Aw shucks, Cindy--it's not so much of a problem to land on Mars, being so light due to 1/3rd of an Earth-gee. So, even without rotational assist, a same-size launcher could reach polar escape velocity (at right angles to the equator) with a lot less boost than on Earth, see? (And please keep your husband out of this.)

*Well, Dicktice, I'm sure many people would breathe a sigh of relief knowing it's not me who has to figure out how to land on or take off from Mars...or Earth...or any other gravity-laden hunk of rock that spins. :laugh: We'd be doomed!

But hey...a girl can try, right?

--Cindy

P.S.: Thanks, Josh!

Shaun Barrett · 2003-03-18 02:49:54

Your early morning revelation concerning force distribution over various areas of Mars' surface doesn't sound right to me I'm afraid, Cindy. It seems like you're reading too much into the problem ... though I could be misinterpreting what you've said.
Earth and Mars both rotate from West to East. If you take the case of Earth, a point on its equator turns one full circle every 24 hours. But Earth's equator is roughly 40,000 kms long. So our point on the equator moves that far every 24 hours. If you move 40,000 kms in 24 hours, you must be moving at 40,000/24 kms per hour, right? i.e. about 1670 kph.
By comparison, someone standing at the north pole has no linear speed at all. They just rotate on the spot every 24 hours.
Now, given that attaining orbit involves accelerating your spacecraft up to very high speeds, and that this involves an enormous expenditure of energy, it obviously makes sense to take advantage of your planet's rotational velocity.
You can see that the best way to do that is to put your rocket on the equator and launch it due East. Even sitting on the ground, its already doing 1670 kph in an easterly direction! So you've got a head start in achieving orbital velocity. If you launch far from the equator or from one of the poles, you lose much or all of this advantage.

But, as has been pointed out in other posts here, Martian gravity, and therefore Martian orbital velocity, are much lower than for Earth. So it isn't such a big deal at Mars anyhow.

Does that help?

May I also add my congratulations on your 10th anniversary. May there be many many more such happy occasions for you both!

Palomar · 2003-03-18 15:48:20

Shaun: "Your early morning revelation concerning force distribution over various areas of Mars' surface doesn't sound right to me I'm afraid, Cindy."

*Hmmmmm. <sad face> Well...I tried.

Shaun: "It seems like you're reading too much into the problem ... though I could be misinterpreting what you've said."

*I'm glad you're too nice and generous a person to tell me I don't know what I'm talking about. I doubt you've misintepreted anything I've said. I'd better stick to philosophy, I guess.

Does that help?

*Yes.

Shaun: "May I also add my congratulations on your 10th anniversary. May there be many many more such happy occasions for you both!"

*Thank you.

--Cindy

Shaun Barrett · 2003-03-18 18:27:57

Cindy:-

I'd better stick to philosophy, I guess.

Even though it may not be one of your principal subjects, Cindy, your grasp of planetary science is far greater than most people ever achieve - and it exceeds my grasp of philosophy by some orders of magnitude!!

And let's not forget your considerable knowledge of astronomy! (Again, leaving me very much in the shade.)
Stick with the philosophy, by all means Cindy, but don't deprive us of your other contributions.

New Mars Forums

Announcement

#1 2003-02-14 10:49:25

Re: Martian Water - New theories with surprising implication

#2 2003-02-15 18:22:28

Re: Martian Water - New theories with surprising implication

#3 2003-02-16 09:47:34

Re: Martian Water - New theories with surprising implication

#4 2003-03-15 11:20:55

Re: Martian Water - New theories with surprising implication

#5 2003-03-15 12:24:58

Re: Martian Water - New theories with surprising implication

#6 2003-03-15 12:35:08

Re: Martian Water - New theories with surprising implication

#7 2003-03-15 12:46:45

Re: Martian Water - New theories with surprising implication

#8 2003-03-15 12:59:50

Re: Martian Water - New theories with surprising implication

#9 2003-03-15 14:26:22

Re: Martian Water - New theories with surprising implication

#10 2003-03-16 08:52:24

Re: Martian Water - New theories with surprising implication

#11 2003-03-17 18:57:11

Re: Martian Water - New theories with surprising implication

#12 2003-03-17 20:09:56

Re: Martian Water - New theories with surprising implication

#13 2003-03-17 20:48:50

Re: Martian Water - New theories with surprising implication

#14 2003-03-17 21:52:34

Re: Martian Water - New theories with surprising implication

#15 2003-03-18 02:49:54

Re: Martian Water - New theories with surprising implication

#16 2003-03-18 15:48:20

Re: Martian Water - New theories with surprising implication

#17 2003-03-18 18:27:57

Re: Martian Water - New theories with surprising implication

Board footer