Re: Venus cratering

"mike3" <mike4ty4@xxxxxxxxx> wrote in message news:1185581778.835092.272530@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi.

This may be dumb, but why does Venus have more impact craters on it
than the Earth, even though it's atmosphere is much thicker and more
pressurized? Shouldn't that eliminate many more potential impactors
_and_ blow stuff around on the surface, eroding the craters away?


The atmosphere of Venus seems to be effective in blocking smaller impactors, because all the craters are larger than several km diameter (I'd need to look up the exact figure). There are several streaks on the surface that have been interpreted as caused by disintegrated asteroids or comet nuclei that created a shockwave or a deposit of material without making a crater.

Or is it due to the lack of liquids like water on Venus (if there is
any liquid on Venus it would probably be from volcanics, ie. lava),
and of plate tectonics (which rearranges the surface and dissects
craters)? Is it that even all that atmosphere is just not as effective
as liquid at moving stuff around? And without plate tectonics that
removes an additional mechanism of crater destruction and obfuscation.

Yes, you have more or less found out why the craters are not eroded away. Given the density of the atmosphere at the surface, wind speeds are very low and there is no liquid precipitation. (Winds in the upper atmosphere are much faster).

The surface is relatively young (of order a few hundred million years) due to tectonic processes. In fact, the age was estimated by counting craters and working out how long it takes to accumulate that many large hits, from the calculated rate of asteroids crossing the orbit of Venus.

The exact nature of the tectonic resurfacing is still controversial. Area by area, or more or less all at once every few hundred million years?


Does this sound like a good idea? Has someone already figured this out?


'Fraid so. Still, nice to see some good thinking.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

.

Relevant Pages

  • Re: Venus cratering
    ... The atmosphere ofVenusseems to be effective in blocking smaller impactors, ... because all the craters are larger than several km diameter (I'd need to ... and of plate tectonics (which rearranges the surface and dissects ... Why doesn't the planet have moving plates like the Earth, ...
    (sci.astro)
  • Re: Any research going on for terraforming venus?
    ... real erosive processes like Earth's rain. ... All of the existing craters are fairly young in geologic terms. ... Major eruptions would also screw up the planet's atmosphere and put all ...
    (sci.space.policy)
  • Venus cratering
    ... but why does Venus have more impact craters on it ... Or is it due to the lack of liquids like water on Venus (if there is ... Is it that even all that atmosphere is just not as effective ...
    (sci.astro)
  • Re: Any research going on for terraforming venus?
    ... Venus has far fewer craters than you'd expect from a world with no real erosive processes like Earth's rain. ... Major eruptions would also screw up the planet's atmosphere and put all the terraforming work to naught. ... jelly and blue-green algae to seed Venus. ...
    (sci.space.policy)
  • Re: planetary heat losses
    ... within the last several hundred million years from an unknown source. ... It's clear that Venus has been globally resurfaced in the last few hundred ... craters, ... That "internal heat" is 100% correct for representing the primary ...
    (sci.space.history)