[meteorite-list] Does Asteroid Vesta Have a Moon?

From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Thu, 07 Jul 2011 19:06:05 -0400
Message-ID: <8CE0B118FB27CC3-1718-CDE02_at_webmail-d171.sysops.aol.com>

If Vesta were to have a Moon, that, IMO would be a major gift from the
heavens should it turn out to be a accreted V-class asteroid (Vestoid).
I'm not sure if the flight plan of DAWN is amenable to any potential
glimpses of a so-called Vestoid, but if more information could be
gathered and analyzed on one or more we would really be in a greater
position to speak of what's going on with some of the HEDX meteorites.
This of course assumes that the HEDs originate from Vesta.

We have to keep in mind that the CRE age of many of the HEDs in our
collections are around 50 million years old or less, perhaps two of
them at ~20 and ~50 million years ago, perhaps not so simple. Since
Vesta is not near the Kirkwood gaps, this makes it highly unlikely that
any of the meteorites come from such young aged collisions, but rather
 from an errant Vestoid or two that percolated into them over the 4
billion (billion=10^9) years since the large impact are postulated. It
would be exciting to learn that the large impact happened 80 million
years or so after proto-Vesta began forming and firm up theories on
what macro events shaped Vesta's history.

Vesta is really a special asteroid in the sense we can see it at
opportune moments from Earth only because it is so bright. This
brightness is postulated to be caused by the light color of the eucrite
material we hold in our trembling meteoritical-friendly hands. It is
basically proposed to be igneous, or a sort of Vesta lava which
collected, perhaps flowing in oceans first, on the surface of the
planetoid shortly after its formation while the radioactive elements
and immense compression developed by gravity still provided and trapped
the heat to the coalescing bodies.

Unfortunately, there aren't any other asteroids that are as visible by
eye and this has to do with size and well as absence of such bright
core material.

While the mission will help with many questions, I think whatever is
deduced will only result in further enigmas and don't hold my breath
for definitive resolution like some might assume of the visit. It will
no doubt prove to be a very convoluted case as was Vesta's impact
history and my fingers are crossed but tempered by remembering the
uncertainties we still have about Earth and the Moon's early impact
history. The idea is this history may be preserved more clearly and we
can hypothesize about it by going to Vesta instead ...

Hopefully the enthusiastically awaited data and its interpretation will
be enough to shut up the suspicious few that say it is not as likely
that HEDs originate from Vesta - a certain distinguished semi-retired
UCLA researcher comes to mind and may yet have the last word, or if it
goes as I hope, conveniently forget that position.

One especially interesting item I hope to hear about is a final answer
as to how that huge crater on Vesta's southern region happened and
still allowed Vesta to remain uniquely intact for our exploration
today. I wonder how hot Vesta became as a result of that impact: does
its age match the 80 million year lapse since accretion mentioned
above?; how this heat was distributed among the latitudes, surface and
deeper core? Being of igneous extraction, I even wonder if a
contribution of a higher thermal conductivity and perhaps lower
friability (for my lack of the more technical term which must exist)
cohesive shell assisted in conserving the body, maybe like the strength
of an egg shell when you try to break it by applying uniform pressure
to a great surface area of it ... the show is about to start!

So a V-class Moon would be great, and while we're wishing, how about a
big V-class meteoroid to slam into Earth to set of the orbital
insertion fiesta at Vesta!

Wouldn't it be great to know if the HEDs, assuming in fact they are
Vesta-derived, are first generation grandchildren of the impact event?
I.e., a large Vestoid (child of the original impact) was smashed and
produce a large proportion of the H-E-D meteoroids that make it to
Earth. A Moon of any size might help depending on luck and the skill of
the analysis, but you probably can see that it's really convoluted -
who's to say we're not 5 generations removed in the impact sense. One
clue we already have on Earth may be the meteorites, and especially the
diogenites which are proposed to be found under the frozen eucrite
surface shell (which itself has a few billion years of residue upon
it). This is why howardites are more likely to contain natural
"meteorite collections" from this lithified residue. But my question,
one minor one when you compare it to all at stake is why the diogenites
are relatively so clean. Does anyone have any interesting inclusions in
their diogenites? How likely is it that multiple-generation impacts
would produce a dirtier meteorite.

Furthermore, there is still one gnawing problem ... that could flip
this whole thing on its north pole. Vesta's brightness itself mentioned
above. With all the space dust and regolith of the billions of years
accumulating - how has it stayed so bright compared to other asteroids
even if it is a one-of-a-kind (ok, there are definitely other
differentiated bodies as evidenced by the different irons, and probably
another smaller asteroid or two discovered with a melted surface),
after billions of years and impacts, why isn't it dirty liike
everything else. Is there a major impact that cooked the whole thing
awaiting discovery? I'm not sure an impact fits, but clearly the
brightness that makes Vesta so appealing here on Earth needs to be
air-tight in its explanation ... All interesting thoughts to consider
IMO.

Isn't it great to have front row seats to Vesta's fiesta?

Kindest wishes
Doug


-----Original Message-----
From: Michael Murray <mikebevmurray at gmail.com>
To: Ron Baalke <baalke at zagami.jpl.nasa.gov>
Cc: Meteorite Mailing List <meteorite-list at meteoritecentral.com>
Sent: Thu, Jul 7, 2011 4:09 pm
Subject: Re: [meteorite-list] Does Asteroid Vesta Have a Moon?


I would bet the excitement is really starting to build for the people
working on this mission. Shouldn't be long now until they can figure
out what Vesta is made up of. Congratulations to everyone involved.?
?
Mike in CO?
?
On Jul 7, 2011, at 11:07 AM, Ron Baalke wrote:?
?
>?
>
http://science.nasa.gov/science-news/science-at-nasa/2011/06jul_vestamoon/?
>?
> Does Asteroid Vesta Have a Moon??
> NASA Science News?
> July 6, 2011?
>?
> July 6, 2011: NASA's Dawn spacecraft is closing in on Vesta, and from?
> now until the ion-powered spacecraft goes into orbit in mid-July, >
every?
> picture of the giant asteroid will be the best one ever taken. What >
will?
> researchers do with this unprecedented clarity??
>?
> "For starters," says Dawn chief engineer Marc Rayman, "we're going to?
> look for an asteroid moon."?
>?
> You might think of asteroids as isolated bodies tumbling alone
through?
> space, but it's entirely possible for these old "loners" to have?
> companions. Indeed, 19-mile-wide Ida, 90-mile-wide Pulcova,?
> 103-mile-wide Kalliope, and 135-mile-wide Eugenia each have a moon. >
And?
> 175-mile-wide Sylvia has two moons. Measuring 330 miles across, >
Vesta is?
> much larger than these other examples, so a "Vesta moon" is entirely?
> possible.?
>?
> Where do such moons come from??
>?
> Rayman suggests one source: "When another large body collides with an?
> asteroid, the resulting debris is sprayed into orbit around the >
asteroid?
> and can gradually collapse to form a moon."?
>?
> Another possibility is "gravitational pinball": A moon formed >
elsewhere?
> in the asteroid belt might, through complicated gravitational?
> interactions with various bodies, end up captured by the gravity of >
one?
> of them.?
>?
> Hubble and ground based telescopes have looked for Vesta moons
before,?
> and seen nothing. Dawn is about to be in position for a closer look.?
> This Saturday, July 9th, just one week before Dawn goes into orbit?
> around Vesta, the moon hunt will commence. The cameras will begin?
> taking images of the space surrounding the asteroid, looking for?
> suspicious specks.?
>?
> "If a moon is there, it will appear as a dot that moves around Vesta
> in?
> successive images as opposed to remaining fixed, like background >
stars,"?
> says Dawn Co-investigator Mark Sykes, who is also director of the?
> Planetary Science Institute. "We'll be able to use short exposures to?
> detect moons as small as 27 meters in diameter. If our longer >
exposures?
> aren't washed out by the glare of nearby Vesta, we'll be able to >
detect?
> moons only a few meters in diameter."?
>?
> While you won't see "find a moon" among the mission's science goals,
a?
> moon-sighting would be a nice feather in Dawn's cap. Not that it will?
> need more feathers. The probe is already primed to build global maps
> and?
> take detailed images of the asteroid's surface, reveal the fine
points?
> of its topography, and catalog the minerals and elements present >
there.?
>?
> Besides, Dawn will become a moon itself when it enters orbit around?
> Vesta. And the probe's motions as it circles will provide a lot of?
> information about the rocky relic.?
>?
> Sykes explains: "We'll use the spacecraft's radio signal to measure >
its?
> motion around Vesta. This will give us a lot of detailed information?
> about the asteroid's gravitational field. We'll learn about Vesta's >
mass?
> and interior structure, including its core and potential mascons >
(lumpy?
> concentrations of mass)."?
>?
> As you read this, the spacecraft is gently thrusting closer to its?
> target. And with the navigation images alone we're already watching a?
> never-before-seen world grow ever larger and clearer.?
>?
> "The pictures are beginning to reveal the surface of this battered,?
> alien world," says Rayman. "They're more than enough to tantalize us.?
> We've been in flight for four years, we've been planning the mission
> for?
> a decade, and people have been looking at Vesta in the night sky for
> two?
> centuries. Now, finally, we're coming close up to it, and we'll be?
> getting an intimate view of this place."?
>?
> This is not only the first time a spacecraft has visited this alien?
> world, it's also the first time a spacecraft has visited a massive >
body?
> we haven't approached previously. In the past, rocket ships have >
orbited?
> Earth, the moon, Mars, Venus, Jupiter, Saturn, and Mercury.?
>?
> "In each case, flyby missions occurred first, providing a good >
estimate?
> of the target's gravity along with information on other aspects of
its?
> physical environment, including whether any moons are present. This >
time?
> we're much less certain what we'll find."?
>?
> At a recent press conference, NASA Planetary Science Deputy Director
> Jim?
> Adams told reporters that Dawn will "paint a face on a world seen
only?
> as a 'fuzzy blob' up to now." What does Rayman think Vesta's face
will?
> look like??
>?
> "Wrinkled, ancient, wizened, with a tremendous amount of character >
that?
> bears witness to some fascinating episodes in the solar system's >
history."?
>?
> If a new moon is among the episodes, Rayman has a name in mind.?
>?
> "How about 'Dawn'?"?
>?
> Author: Dauna Coulter?
> Editor: Dr. Tony Phillips?
> Credit: Science at NASA?
>?
> More Information?
>?
> Dawn Journal <http://dawn.jpl.nasa.gov/mission/journal_06_23_11.asp>
> --?
> penned by Dawn's chief engineer Marc Rayman?
>?
> Footnotes:?
>?
> (1) In addition to having moons, asteroids can also be double: Binary?
> asteroids <http://apod.nasa.gov/apod/ap001101.html> sometimes form >
when?
> a spinning parent body splits. The body is spun up by a phenomenon?
> called YORP that occurs when the body absorbs photons from the sun
and?
> reradiates them as heat: more?
> <http://www.news.cornell.edu/stories/March07/margot.yorp.html>.?
>?
> (2) Dawn will perform dedicated observations in search of moons for?
> about 15 hours. However, if no moon is found at Vesta on July 9th, >
that?
> doesn't mean there isn't one. Rayman says: "If there is a moon, it >
might?
> show up by coincidence in other observations, but we have no other?
> observations dedicated in this mission to finding a moon. There is >
just?
> so much to learn about Vesta itself, that that is where we are >
focusing?
> our time."?
>?
> (3) From NASA press release: When Vesta captures Dawn into its orbit
> on?
> July 16, there will be approximately 9,900 miles (16,000 kilometers)?
> between them. When orbit is achieved, they will be approximately 117?
> million miles (188 million kilometers) away from Earth. During the?
> initial reconnaissance orbit, at approximately 1,700 miles (2,700?
> kilometers), the spacecraft will get a broad overview of Vesta with?
> color pictures and data in different wavelengths of reflected light.
> The?
> spacecraft will move into a high-altitude mapping orbit, about 420 >
miles?
> (680 kilometers) above the surface to systematically map the parts of?
> Vesta's surface illuminated by the sun; collect stereo images to see?
> topographic highs and lows; acquire higher-resolution data to map
rock?
> types at the surface; and learn more about Vesta's thermal
properties.?
> Dawn then will move even closer, to a low-altitude mapping orbit?
> approximately 120 miles (200 kilometers) above the surface. The >
primary?
> science goals of this orbit are to detect the byproducts of cosmic >
rays?
> hitting the surface and help scientists determine the many kinds of?
> atoms there, and probe the protoplanet's internal structure. As Dawn?
> spirals away from Vesta, it will pause again at the high-altitude?
> mapping orbit. Because the sun's angle on the surface will have?
> progressed, scientists will be able to see previously hidden terrain?
> while obtaining different views of surface features.?
>?
> Credits: Dawn's mission to Vesta and Ceres is managed by JPL for?
> NASA's Science Mission Directorate in Washington. Dawn is a project
of?
> the directorate's Discovery Program, managed by NASA's Marshall Space?
> Flight Center in Huntsville, Ala. UCLA is responsible for overall
Dawn?
> mission science. Orbital Sciences Corp. of Dulles, Va., designed and?
> built the spacecraft. The German Aerospace Center, the Max Planck?
> Institute for Solar System Research, the Italian Space Agency and the?
> Italian National Astrophysical Institute are part of the mission
team.?
> JPL is managed for NASA by the California Institute of Technology in?
> Pasadena. For more information about Dawn, visit:?
> http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov?
> <http://dawn.jpl.nasa.gov/> . You can also follow Dawn on Twitter at:?
> http://www.twitter.com/NASA_Dawn .?
>?
>?
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Received on Thu 07 Jul 2011 07:06:05 PM PDT