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As someone who has been following the rover mission on a daily basis since their landings, I am dismayed by the avidity with which NASA describes evidence of water--as if large bodies of water probably existed--and their unwillingness to ever bring up the possibility that no large waters of liquid water ever existed.
This weeks "Economist" gives an unvarnished account of what NASA has found that does not jibe at all with their heroically optimistic web articles.
The Economist says that so far NASA has found no signs of life (while admitting the rovers were not set up for that) and that at most, a thin film of very salty brine may have covered some large areas. The so-called sedimentation layers are more likely to have been produced by successive wind-born deposits of dust.
For more on this NASA salesmanship (for a maned mission), see: http://www.velocitypress.com/pages/water_on_mars.php]http://www.velocitypress.com/pages/water_on_mars.php
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There is an enormous amount of evidence for liquid water. You don't need a geology degree to be able to look at a few pictures of Mars and see fluvial erosion. It's there and it's obvious.
"In the beginning, the Universe was created. This made a lot of people very angry and has been widely regarded as a bad move."
-Hitchhiker's Guide to the Galaxy
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My guess is that everyone is correct about water on Mars. There must have been great amounts of water to create all the channels that are visible. However, the water may not have been liquid for very long--maybe just weeks to a few decades. The water would quickly form a layer of ice, slowly freeze, then slowly sublime (go directly to a gas). More likely, the ice would have been covered over with dust which would keep the water and ice around much longer. There seems to be much evidence for some of the ice to still be around. A recent article in the journal Science discusses glaciers on some of the volcanoes and in and around Hellas.
Much ice has been discovered poleward of 60 degrees in both hemispheres. Basically, after about a meter, the ground contains mostly ice in those locations. So, if you dug down a meter, a bucket of the dirt at the bottom would be over 50% ice.
The poles both contain about a km or two of ice. That area is about twice the size of AZ.
The minerals examined by the Rovers have been modified by water. But, much of the alteration could have been done from films of water that are only a few molecules thick. The reasoning is that at times the rotational axis of Mars changes. During that time, the water at the poles and in frozen in the ground poleward of 60 degrees melts. Much or most or all of it will turn into a gas, travel to a cold place (near the equator) and condense as frost. Durnng the thousands of years when this is taking place, huge amounts of ice will accumulate in certain areas. At times during the year, it will be warm enough for the water to melt and flow--that is when minerals can change or maybe a dormant life form will grow and reproduce. Of course a large meteorite could strike and melt the ice and form channels in the process. Alternatively, magma may move around and melt the deposits.
This is my understanding of the water question for Mars. In the past year of so a lot of good articles have appeared in journals--especially Nature and Science. On my website, I have about 100 links to information about Mars. In one section, I've listed sources for many articles.
http://paws.flcc.edu/~secoskjj
Isn't it a great time to be alive to learn about Mars.
Jim Secosky
My website contains photos from Mars taken by amateurs with the Mars Global Surveyor.
paws.flcc.edu/~secoskjj
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