QUOTE (Paul Murphy @ Jul 29 2008, 06:15 PM)
Although, to be honest, all you've done is show me how little I know -and I already get more than
enough lessons in humility from my six year old
I usually get multiple lessons in humility every day (also known as scientific frustration): either from someone more knowledgeable than myself, or from chemistry that doesn't work, or from biological systems that don't behave the way I thought they would.
Either way, I hope that I learn a little more for the next time. But sometimes I don't
QUOTE (Paul Murphy @ Jul 29 2008, 06:15 PM)
1 - I don't get this low strength surface rock business. How does it get made?
For Mars, volcanic eruptions throw up large amounts of loose dust and little particles that go a looong way. (Low gravity, low atmospheric friction.). Then you've also got infalling dust. And then you've got meteor impacts over the millenia spraying impact debris (surge clouds) all over the place as well. Add to that eons of wind erosion picking up dust and moving it from one place to the other and you get large amounts of dust and dune sands. Some of these get compacted and form fossilized dune sand structures. (Burns Formation and Victoria Crater show the neat-o crossbedding of fossilized dune sands.)
Without tectonic cycling to stuff rock in trenches and bring it back up and shuffle it around, most of the terrain pretty much stays where it is. So you've billions of years of wind depostion, wind stripping and impact gardening in play.
QUOTE (Paul Murphy @ Jul 29 2008, 06:15 PM)
2 - for water to move rapidly and in larger quantities or over longer time periods from A to B (thereby making a canyon) there either has to be a very large source of water at A or some way of getting it from B back to A. Does Mars get enough solar energy to power the B to A part of this cycle in any atmospheric conditions thought to have been possible there? If not, where did the water at A come from?
It is possible the water made a one-way trip. Frozen subsurface aquifer, catastrophic release, up in the atmosphere, and stripped away by the solar wind. The canyons are thought to have been carved early in Mars history (3.5-3.8 billion years ago).
Hopefully an isotopic measurement (soon?) by the Phoenix spacecraft might shed light on this. Lotsa light isotopes, the water has been locked up in the polar subsurface for a long time. Lotsa heavy isotopes, it's been in equilibration recently.
QUOTE (Paul Murphy @ Jul 29 2008, 06:15 PM)
Perhaps you could recommend some appropriate reading?
Wikipedia/Mars is an awesome place to start (and references therein)
[Y'all can debate me on Wikipedia, but every time I go into a new area I hit Wikipedia first, and I'm always amazed at the depth and accuracy of the information dredged up.]
Another winner is to browse the Lunar and Planetary Science abstracts. They are excellent tight pieces of information that are very accessible to the interested amateur.
Favorite [old] books I really like are (lotsa good diagrams of fundamental processes):
Murray, Malin, and Greeley, "Earthlike Planets: Surfaces of Mercury, Venus, Earth, Moon, Mars", W.H Freeman and Co., 1981.
Carr, "The Surface of Mars", Yale Press, 1981.
-Mike