[CraigS]

Originally Posted by orestis

Thanks Craig,

Your answers are right on the mark.

Spectroscopy is used to find out the chemical composition of stars can't they use it to find out the ratio of dry ice to water ice.Or is this a very difficult process.

Spectroscopy can be (and has been used) to determine the composition of the atmospheric gases surrounding Mars. From these measurements, CO2 comprises about 95% of the atmospheric gas. Water vapour is only about 0.03 %. So there is almost no water vapour. This might be because any water on the Martian surface is frozen. If it is frozen, the bulk of it would probably be found on the poles. In a way, the atmosphere should be an indirect indicator of the proportions.

Spectroscopy works if the samples are vapourised to release the gases.

Spectroscopy was used by a recent lander in its little laboratory, to determine the amounts of chemicals in the scoops they took. They did this by heating the sample until the gases were released, and then measured the 'absorption' wavelengths corresponding to the chemical composition of samples. The proportions of the compounds and elements in the sample could then be determined. I think they only got one reading, unfortunately.

This is the same process used to measure the gases in the atmospheres of stars. We can do this remotely from Earth, because the star vapourises the gases and provides a background light source.

Lets use a little imagination here.Suggest there was a lot of water on mars creating the river valleys and other geological features,How could it all disappear,just like that.

They have ideas and hypotheses. I think the leading hypothesis is that any liquid H2O may still exist underground. It may have burned off, if Mars' magnetic field, (if it ever had one like Earth's), diminished (for unknown reasons). Either way, we probably need to go there to find out the real answers ! There is undeniably, a lot of geological evidence. I can also 'imagine' that there may have never been any 'big water' there and other unknown processes may explain some of the geological features. The geological processes on Mars could easily be ones we don't understand because the physical conditions on Mars are completely, (& quite radically), different from those here on Earth. Using Earth as a model could conceivably, result in the 'mystery' you speak of. We don't know, what we don't know, yet.

Just wondering, Can you have life that can breathe co2 on earth?
I know trees can but they also need oxygen during the night but then again they make oxygen so maybe its just a big cycle.

Life (as we know it) needs to be able to metabolise (eat to release energy to do its thing). The energy stored in the CO2 molecule could be released to provide the energy which could be used by extra-terrestrial life. The soil on Mars contains 'perchlorate'. This possibly, could perform the same job. Complex topic.

I'm no biologist, but clearly all plant life on earth undergoes a metabolic cycle called photo-synthesis which uses CO2 for them to 'do their thing'. I think there are bacteria here, which can do the same.

Cheers