[meteorite-list] Mercury Fragments on earth (not)
From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 4 Aug 2011 13:51:38 -0500
Mercury Fragments on earth (yes).
Calculating the likelihood of a Mercurian rock arriving here
is a bit more complex, just as for rocks from Mars and the Moon.
What you need is large-scale numerical integration. Sit back
and let Mr. Newton's laws do the work. Let the teraflops roll.
Have a beer.
Fortunately we got that. Brett Gladman is the pioneer in that.
Logic is always convincing (you should listen to that Aristotle
guy talk) but deduction is not the way to go here.
Abstract of Gladman paper on Mercury with new results
suggesting the Mercurian influx is considerable and implying
that we got'em and we don't know it:
and a better summary of that paper:
A-Ha! Here's the full paper::
For all transfered materials, Lunaites, Martians,
Mercurians, etc...The original Gladman paper (abstract)
on the transfer of material between the planets, done
back when we first discovered it was happening:
A really (book-length) treatment of planetary material
transfer by Gladman:
Sterling K. Webb
----- Original Message -----
From: "MexicoDoug" <mexicodoug at aim.com>
To: <Meteorite-list at meteoritecentral.com>
Sent: Thursday, August 04, 2011 2:59 AM
Subject: [meteorite-list] Mercury Fragments on earth (not)
> Dear List,
> Mercury as a source for meteorites arriving on earth seems like the
> most unlikely occurrence. I hope someone can point out where I am
> wrong, since it would be wonderful to imagine the possibility that
> material from the Swift Planet could every make the upstream trip
> here. It is easy to think hey ... we have Lunar and Martian material
> here, dream of Vestal material, so why no Mercury, Venus, etc... as if
> all were equally possible.
> But they are not equally possible. Far, Far, Far from equally
> possible. If things were equally possible all you would have to do is
> ask two supermodels out on a date, and odds are one would accept,
> right? - There are only 2 answers and *if we assume yes/no is a 50/50
> proposition...* ? Hmmm ... a most unlikely occurrence.... and for
> most not a 50/50 probability. Same goes for this present case.
> The Moon is obviously within Earth's gravitational domination, so it
> is natural that we would have a high possibility if material falling
> here if it can escape the moon (escape velocity: 2.4 km/s), and Earth
> is the local drain for the moon.
> Mars (escape velocity: 5.0 km/s) is upstream from the Sun to Earth so
> it doesn't seem like any surprise that fragments ejected could find
> their way to Earth.
> So why not a Jupiter meteorite? I don't think that is likely since
> Jupiter (escape velocity on 'surface' 59.5 km/s) extremely greedy with
> its material, requiring escape at five times faster than on Earth.
> But what about Mercury. Mercury's escape velocity is 4.3 km/s. But
> it's downstream from Earth and the Sun is a huge gravitational drain
> plug that devours material. If you think Earth gets a piece of Mars,
> imagine what the Sun gets from Mercury. To escape the Sun ... that is
> to go upstream towards Earth, at Mercury, any fragment would have to
> battle an escape velocity of 67.7 km/s. That's greater than Jupiter !
> You might say ... ok, you don't have to actually escape the Sun, only
> make it from Mercury to Earth. Well, at Earth, the escape velocity is
> 42 km/s from the Sun. That's a loss of 25 km/s ... and don't forget
> the extra 4.3 km/s to get away from Mercury as well ...
> Their numbers are probably greater than summing them, but let's just
> do that so it stays simple call it a minimum of 30 km/s imparted
> velocity to tether that fragment of Mercury to Earth. What lucky rock
> ejected by chance in the direction of Earth could handle that energy
> and board a greyhound (bus) to Earth?
> It seems to me about as likely that we'd get a fragment from Jupiter's
> surface if indeed there is a surface instead of a thick damping stew.
> Once something (plasma?) gets ejected from Jupiter, though it is
> smooth sailing to Earth if the direction happens to be right because
> the Sun still sucks up anything not in a circular or ellipsoid orbit,
> like the big drain hole that got the whole solar system moving to
> start with. (Yes, everything orbits the Sun for pretty much the same
> reason the water makes circles around the hole in toilet bowl on its
> way down).
> So if by brute force, Mercury is unlikely to be a source of material,
> how about by some other celestial mechanism? Something similar to
> Jupiter's orbital resonances, perhaps? I don't think that is very
> likely. Earth would be the Jupiter by mass, though Venus might be
> argued. But Mercury is not the Swift Planet for nothing ... there is
> no way orbital resonance could build up with Mercury constantly
> swinging by.
> It gets rapidly less likely anything else might work ... like, how
> about a hand-off from Mercury to Venus then to Earth. The energy is
> still huge to get to Venus, but unless JPL tweaks a slingshot out of
> it with the assistance of propulsion, I just don't see it happening.
> Well, then I would think the argument dropped to a statistical one ...
> It would be ... very very unlikely but when 10,000,000,000 pieces are
> ejected from Mercury and 0.000001% actually do this *a miracle
> happens* and we are left with 100 meteorites that make it to Earth.
> OK, but by the same logic then there would be 1,000,000,000 lunar
> meteorites lying around. So go find one ... no ... make that go find
> two - from Mercury, I mean. Angrites are more than two... Kind of
> weakens the angrite theory.
> The last resort might be to argue a hugely eccentric orbit with a
> major axis reaching earth. I don't know about this one, but there is
> the detail of Venus clearing its own neighborhood, not to mention
> Mercury and Earth runs at a snail?s pace compared to them. There are
> no Vulcanoid asteroids and so, so so few Interior earth Asteroids ...
> like a dozen? And how eccentric are their orbits ... Maybe some
> asteroid scanning guy can speak authoritatively here but I have a
> feeling that the answer won?t budge from almost nothing to nothing
> plus epsilon.
> Anyway, ET's angrite without equal and amazing story of adventure that
> goes with it ... got me to thinking about the debate we've heard many
> times now and when I look at these numbers, I just can buy it. Is
> there some other argument being made that was omitted here ... besides
> Mercurians shooting at Earth with scaled up accelerator space guns? I
> hope so, but darned if I can think of it! The situation is very
> different from Vestoid since there is no supraJupiter undisturbed ...
> around with billions of circulating rocks smashing into each other
> much further away from the Sun's powerful gravitational grasp.
> Kindest wishes
> Visit the Archives at
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
Received on Thu 04 Aug 2011 02:51:38 PM PDT