[S0122017]

You sure know how to be defensive in a discussion.
Those "erosional features" could not have arisen from the occasional rain. Some are deeper then the grand canyon.

Sure, there are no roots to hold soil together, but any comet-vapor-rain event would not occur every other day now, would it? We have been watching mars for a short while now and i haven't heard of it.

[SunkenCiv]

You sure know how to be defensive in a discussion.

I sure know how to discuss things, if that's what you mean.

Those "erosional features" could not have arisen from the occasional rain. Some are deeper then the grand canyon.

Again, a straw man argument.

Sure, there are no roots to hold soil together, but any comet-vapor-rain event would not occur every other day now, would it? We have been watching mars for a short while now and i haven't heard of it.

Mars is covered with craters, and those were caused by impacts.

Water erosional features have been seen on Mars. I'm a little surprised that you'd oppose that concept, since you think snow used to fall on Mars, and snow is made of water.

Mars' mass and density are such that its atmosphere is today about what it has been for a very very long time (not a mere 50,000 years, but millions of them), and liquid water can't exist on Mars because of the low atmospheric pressure.

Any purported snowfall on Mars would itself have to result from the impact scenario -- the vapor would lose energy some time after and distance from the impact, refreeze, and precipitate.

The seasonal growth and shrinkage of the polar icecaps would be due to the arrival of solar radiation or lack thereof. But it doesn't mean Mars can be terraformed.