Confirmed: Water Once Flowed On Mars 113
An anonymous reader writes "A new study based on observations last September by the Curiosity rover on Mars has confirmed that pebble-containing slabs of rock found on the Martian surface were part of an ancient streambed. The work provides some of the most definitive evidence yet that water once flowed on Mars. '[The pebbles'] smooth appearance is identical to gravels found in rivers on Earth. Rock fragments that bounce along the bottom of a stream of water will have their edges knocked off, and when these pebbles finally come to rest they will often align in a characteristic overlapping fashion. ...It is confirmation that water has played its part in sculpting not only this huge equatorial bowl but by implication many of the other landforms seen on the planet.' According to NASA, 'The stream carried the gravels at least a few miles, or kilometers, the researchers estimated. The atmosphere of modern Mars is too thin to make a sustained stream flow of water possible, though the planet holds large quantities of water ice. Several types of evidence have indicated that ancient Mars had diverse environments with liquid water. However, none but these rocks found by Curiosity could provide the type of stream flow information published this week. Curiosity's images of conglomerate rocks indicate that atmospheric conditions at Gale Crater once enabled the flow of liquid water on the Martian surface.'"
Sun cycles (Score:3, Interesting)
And it will again. I'm convinced that the sun has hot and cold cycles. As it warms up, the water on Earth will be vaporized and the ice on Mars will melt. Then it cools and reverses that. Nature's test then is can we develop far enough quickly enough to get to the other planet before it's too late. Of course, this is just idle conjecture. :)
Re:Need it have been water? (Score:4, Interesting)
There is no such thing as liquid CO2. Only artificially high pressures can prevent it from sublimating, and as I'm sure you realize, a planet that can't even retain its atmosphere is unlikely to have somehow maintained an atmospheric pressure 5 times that of the Earth in the past.
Water is an extremely common and simple substance that you can find all over the universe.
So according to Occam's razor... what else could it possibly have been?