Venus cratering

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?

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.

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

"mike3" wrote in message
oups.com...
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)

On Jul 28, 1:37 am, "Mike Dworetsky"
wrote:
"mike3" wrote in message

oups.com...

Hi.

This may be dumb, but why doesVenushave 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 ofVenusseems 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 onVenus(if there is
any liquid onVenusit 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 ofVenus.

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?


Hmm. Why doesn't the planet have moving plates like the Earth, anyway?



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

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


Of course if you come upon it without any foreknowledge of the
previous
figuring out it's still a bit of a treat.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)