|
Posted by Brian Davis on June 7, 2007, 9:14 pm
Please log in for more thread options
> I think I've found a pretty good explaination for the many ovoid
> craters on Mars.
At least one paper has proposed (some time ago) that there may have
been a population of other small moons that have been deorbited by
tidal forces. They even proposed that the orientation ofthese craters
shows two distinct populations (based on the orientation of the long
axis), suggesting that the spin axis had changed over time.
> So how did Mars pick up all of these plunging moonlets?
Likely the same way it managed to get Phobos and Deimos. Which, i
admit, is still a bit of a mystery.
> recent analysis of Deimos and Phobos left off, showing
> them to have the compositional characteristics of mainly
> water ice...
Reference? Bulk anaylsis of these should be a bit challenging, given
the well-laundred surfaces. A bigger problem is that water ice isn't
stable at the orbit of Mars, so a icy ring in the first place couldn't
last.
> If the oblong craters are found to contain more water
> than their surroundings, then this falling ice hypothesis
> might find more support.
Any impactor (ice or rock) would be hitting with more than enough
kinetic energy to completely vaporise, so you wouldn't expect such
impact to deposit water at the impact points (quite to the contrary -
upon impact, these would be some of the hottest points on the
surface). If they did contained enhanced water, it must have been
deposited well after the crater-forming impacts.
> Also, if any amount of ice fell in the other direction--out of Mars
> orbit--perhaps traces can be detected.
Things don't "fall" in or out of orbit - if something ends up
deorbiting ice chunks, it's hard to figure out how it would add energy
as well... and where those tiny bits would be by now, well...
--
Brian Davis
| 
XML Sitemap