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

From: Richard Montgomery <rickmont_at_meteoritecentral.com>
Date: Thu, 7 Jul 2011 18:09:25 -0700
Message-ID: <3463109ABF2C4BEEAA47BCCDA21D0675_at_bosoheadPC>

List,

Considering the possible plausibility of a pending companion 'moon' orbiting
Vesta (or two???); and considering Mexico Doug's last contribution.... I
pose a question:

How could that grand ol' impact evidentiary-crater produce a moon of the
ssame petrologic composition of Vesta's primary/current achondritic
compostition be similar, due to a greater resultant mb-recrystalization from
impact, than the host?

Curious,
Richard Montgomery




----- Original Message -----
From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Thursday, July 07, 2011 10:07 AM
Subject: [meteorite-list] Does Asteroid Vesta Have a Moon?


>
> 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 09:09:25 PM PDT