Nasa is to reveal Mars water secrets...

[KennyR]

Blobrana wrote:
i`ve got a feeling that mars is crawling with underground lifeforms...er, like the earth...

Well, they obviously don't use sunlight, or Mars would be green. So they would have to live off warmth and sulphides produced by volcanism. Trouble is, unlike Earth, Mars cooled out a long time ago. No more volcanism. So where would they get their energy from?

[KennyR]

Speelgoedmannetje wrote:
Well, in the deepest parts of the sea here on earth, weren't there lifeforms based on sulphur (and so), other than well where we're based on?


so these probably work different.

Why HAS it to be green?

Nope, it's a matter of chemistry. At the temperature ranges where water could be used as a solvent for life (0-100C of course), green chlorophyll happens to be the most efficient chemical for photosynthesis. There are other kinds - brown, red...but these are a lot less efficient and are used by plants that don't have any other choice, like deep seaweeds. It's hard to imagine single-celled bacteria with brown or red chlorophyll being able to survive in the limited sunlight and low temperature Mars provides.

[KennyR]

green chlorophyll happens to be the most efficient chemical for photosynthesis

How do you know that? Source?

Look outside.

Evolution is a hard taskmaster. It always goes for the most efficient processes. Less efficient ones just die and disappear, except in places the more efficient ones don't work.

[KennyR]

Speelgoedmannetje wrote:
F evolution 'found' a better way.

Nature is far far far from perfect y'know. And evolution is still going on.

It had about two billion years to perfect photosynthesis before animals started to appear. It's had plenty of time. There is nothing more efficient than blue-green chlorophyll, because if there was, it would be here.

And why should it be green on Mars? Maybe there's happening the same, but less/more efficient.

Then where is the oxygen by-product?

[KennyR]

Quixote wrote:
Ken, there are trees near my house that are purple. The color may be due to other elements in the leaves besides the chlorophyll, but the point is that they don't look green to the eye, or camera.

Wrong, they do - to a spectrographic camera. Those chlorophyll lines will be there and strong. Mars has no such lines. Therefore, Mars has no photosynthesising life.

[KennyR]

AfterThought: It is often stated, that mars is too small to sustain a sizable atmosphere neccessary to sustain a living planet. I believe this to be wholey untrue, but rather, that mars had it's atmosphere destroyed by a very massive impact, after most of the free material in the solar system that could replinish it's atmosphere had dissipated. the evidence is in the southern hemisphere, a crater 6 miles deep.

The atmosphere of Mars isn't thick for one reason - solar wind. Because Mars is so small, its iron core cooled and solidified a long time ago. The magnetism it generated that was protecting the atmosphere disappeared, and the solar wind stripped off what remained of the atmosphere.

It's the eventual end of all rocky planets, although it happens to the smaller ones (or the low-iron ones) first. Earth really is quite exceptional in every way.

[KennyR]

Karlos wrote:
Now, given venus also has no appreciable magnetic field and is exposed to much higher levels of solar wind than mars (given its larger and closer) and retains a vast atmosphere, how much damage to mars' atmosphere is the solar wind producing I wonder?

Venus has its own Van Allen belts. Even so, it doesn't prevent some of its atmosphere being blown into a torus in wake of its orbit.

The fact that Mars has no thick atmosphere due to solar wind erosion is the current scientific theory right now. I don't know how to check your calculation but 12% does seem rather a little.

[KennyR]

ivier wrote:
Green however is NOT neccessarily as efficent as chlorophyll can get, just the most efficient, that earth life has found. 95% of all plant species on earth use green chlorophyll, but theres still the other 4.9999999% using purple. but there are other chlorophylls as well, they are quite rare, usually found in unusual algae and moss.

To say mars has no photosythisizing life because there is no green, is the same as saying, a city has no taxis, because there are no yellow cars.

Chlorophyll B, C and D all have spectral characteristics identifiable by high school students. So if they're there in any quantity they'll have been seen. They weren't. Besides which, A is the most efficient, and it's difficult imagining anything surviving on the less efficient types in an environment as hostile as Mars.

Not only does this city not have any taxis, it has no roads.

[KennyR]

Karlos wrote:
So again, how come the atmosphere is still so vast after so long?

Seems I was wrong about Venus having a geomagnetic field. But it seems the very thickness of its atmosphere generates a magnetic field of its own capable of deflecting solar wind. Clicky here for some in-depth info.

[KennyR]

T_Bone wrote:
Hell, who's to say all life would even be carbon based to begin with? here we are looking for green and carbon dioxide, while it's possible there's grey's excreting sand as a byproduct of silicone based respiration.

Silicon-based life will never be anything more than sci-fi. Silicon shares many properties with carbon, but it does not form long chains. Carbon forms a bewildering number of compounds. Silicon does not. It's too metallic and doesn't like covalent bonds - especially not with itself.

Silicon makes rocks. Carbon makes chemistry.

It may be boring to most people, but the reason life is carbon based and green is the same way large planets are round - they just can't be any other way.

[KennyR]

Insects are not the ideal life form for low oxygen environments anyway. They don't even have lungs. Or haemoglobin, for that matter.