Gareth Slee wrote:

Water has flowed on Mars in the last 7 years...
http://www.nasa.gov/mission_pages/mars/main/index.html




Water has _possibly_ flowed on Mars in the past seven years.
Which is a pretty neat trick, as the temperature at the surface is
generally (if not always) below freezing, and the photo that they are
showing shows whatever was flowing came out near the surface and ran
down the inside of the crater.
I'd believe in sub-surface heating and liquid water if I could see some
evidence of a active volcano up there.
On the other hand, there is a substance that has three forms inside the
Martian pressure and temperature curve.
Carbon dioxide - we know it exists in a gaseous state on Mars (it's most
of the atmosphere) in a solid form (the polar caps), and as we recently
found out, erupts in geysers at the polar regions as they warm in spring.
So if something's rolling down crater walls, its very probably liquid
CO2, not water.
But the PAO is at work again.

Pat