[meteorite-list] Venus May Have Once Had A Moon

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Thu Oct 12 15:37:01 2006
Message-ID: <20061012193656.89323.qmail_at_web50904.mail.yahoo.com>

Sadly no, I don't. They were all in my astrophysics
notes from uni but they got thrown out in a house move
about 18 months ago. I suppose I could hunt around for
something. I kept my textbooks, maybe theres something
in there.

Rob McC
--- tett <tett_at_rogers.com> wrote:

> Rob,
>
> Do you have your graphs and calculations available
> in an email format? I
> would love to review this and try to understand your
> argument.
>
> Cheers,
>
> Mike Tettenborn
> ----- Original Message -----
> From: "Rob McCafferty" <rob_mccafferty_at_yahoo.com>
> To: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>;
> <meteorite-list_at_meteoritecentral.com>
> Sent: Wednesday, October 11, 2006 3:57 PM
> Subject: Re: [meteorite-list] Venus May Have Once
> Had A Moon
>
>
> > I've been saying this for years. I even tell my
> > classes.
> >
> > If log angular momentum is plotted vs log Mass,
> all
> > planets fit nicely on a line except Venus and
> Mercury
> > (Earth/moon system needs to be combined).
> > Now since angular momentum is a conserved
> quantity, it
> > matters not one jot how far a planet and its moon
> > drift apart. Combine the angular momentum of Venus
> and
> > Mercury and they slot nicely on the line like all
> the
> > others.
> > If some accuse me of favouring an idea which is
> too
> > neat, I'd accuse the author of this article of
> this
> > article of over-thinking a problem. The peculiar
> > rotation of venus is rather nicely explained by it
> > losing a moon, especially one as big as Mercury.
> >
> > Rob McC
> > (plagariser of his Professors Ideas)
> >
> > --- Ron Baalke <baalke_at_zagami.jpl.nasa.gov> wrote:
> >
> >>
> >> http://skytonight.com/news/4353026.html
> >>
> >> Why Doesn't Venus Have a Moon?
> >> by David Tytell
> >> Sky & Telescope
> >> October 10, 2006
> >>
> >> Back when Earth was very young, our home world
> was
> >> steadily pummeled by
> >> large solar system debris. While Earth withstood
> the
> >> barrage of hits
> >> like a prizefighter that wouldn't fall down, one
> >> blow nearly destroyed
> >> the world. A Mars-size body plowed into us,
> >> completely disrupting both
> >> bodies and splashing massive amounts of debris
> into
> >> orbit which, most
> >> astronomers agree, coalesced to form our Moon.
> >>
> >> But if something that large hit us, how did our
> >> nearest-neighbor planet,
> >> Venus, dodge the same fate? According to a new
> >> study, it didn't.
> >> Billions of years ago, according to work
> announced
> >> yesterday, Venus once
> >> had a moon that formed the same way Earth's did.
> >>
> >> On Monday at the American Astronomical Society's
> >> Division of Planetary
> >> Sciences meeting in Pasadena, California, Caltech
> >> undergraduate Alex
> >> Alemi presented models created with David
> Stevenson
> >> of Caltech that
> >> suggest Venus was not only slammed with a rock
> large
> >> enough to form the
> >> Moon, the event happened at least twice.
> >>
> >> According to Alemi and Stevenson, in models of
> the
> >> early solar system it
> >> is nearly impossible for Venus to avoid a big
> hit.
> >> Most likely, Venus
> >> was slammed early on and gained a moon from the
> >> resulting debris. The
> >> satellite slowly spiraled away from the planet,
> due
> >> to tidal
> >> interactions, much the way our Moon is still
> slowly
> >> creeping away from
> >> Earth.
> >>
> >> However, after only about another million years
> >> Venus suffered another
> >> tremendous blow, according to the models. The
> second
> >> impact was opposite
> >> from the first in that it "reversed the planet's
> >> spin," says Alemi.
> >> Venus's new direction of rotation caused the body
> of
> >> the planet to
> >> absorb the moon's orbital energy via tides,
> rather
> >> than adding to the
> >> moon's orbital energy as before. So the moon
> >> spiraled inward until it
> >> collided and merged with Venus in a dramatic,
> fatal
> >> encounter.
> >>
> >> "Not only have we gotten rid of the moon, but
> we've
> >> also done well to
> >> explain Venus's current slow rotation rate [and
> >> direction]," says Alemi.
> >> If a second moon formed from the second
> collision,
> >> it too would have
> >> been absorbed the way the first one was.
> >>
> >> The models do allow for more than two impacts,
> but
> >> the probability of
> >> Venus enduring several massive collisions is low.
> >> "You can do this with
> >> multiple collisions, but the hypothesis is that
> [the
> >> net result] adds up
> >> to a negligible contribution" to the planet's
> final
> >> state, says Alemi.
> >>
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> >
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Received on Thu 12 Oct 2006 03:36:56 PM PDT