On Jan 5, 1:06 pm, Tom Adams <[email protected]> wrote:
> Can you cite something, anything, that claims that Earth protected
> Venus from icy asteroids?
>
> You can find discussions and explanations of the number of craters on
> Venus, but I can't find any that mention the protective effect of the
> Earth. Seems an odd omission if there is a protective effect.
I did try to find where I first heard of Earth's water being delivered
by the icy asteroids, but have failed. The first citation I gave was
obtained with a quick Google search in order to justify my
(surprising) statement.
Venus is dry, and it may have occurred to me that Earth intercepting
the asteroids would explain that dryness, but as I recall it was given
as a reason for the dryness of Venus. If I can find my original source
I will at least be able to confirm or deny whether it does claim that.
BTW, the lack of evidence of for the Late Heavy Bombardment at 3,800
Ma (old craters) on Venus cannot be due to a shielding by Earth. It
is because Venus was resurfaced around 700 Ma, so even if the old
craters formed they would not be there now.
Also, I found this at
http://www.space.com/scienceastronomy/090105-mm-venus-water.html
deagleninja wrote:
"I would think our relatively giant moon would help us capture many
more icy comets throughout our early history than Venus. It's presence
extends the gravitational effect of our system an additional quarter
million miles does it not?"
Of course at 3,800 Ma it would have extended the radius by less than
the current 250,000 miles.
OTOH, we are talking about asteroids that start out close to Jupiter.
As the major axis of the asteroid was extended, the asteroid might
have reached Jupiter before the minor axis was small enough for it to
reach Venus. In that case, would Jupiter be the frontstop? It may be
easy to check with the right data, whether the asteroid could mmet
earth but not Venus before reaching Jupiter. We know roughly the
initial solar orbits of the icy asteroids - greater than 3 AU to
Jupiter's 5 AU and Venus at 0.723 AU.
Cheers, Alastair
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