[meteorite-list] Does Asteroid Vesta Have a Moon?
MexicoDoug
mexicodoug at aim.com
Fri Jul 8 02:04:01 EDT 2011
"Thus the range of upward velocity (in is 247 to 350 m/s for Vesta.
That's a big chunk of range. In English units 552 mph to 783 mph
(cruising speeds for commercial airliners up to about Mach 1)."
should read range of orbital velocity ...
"upward" was going to be in there for another thought that the velocity
to orbit cannot be in the radial (upward) direction and sent ...
to see this in action watch the planned space shuttle shot in a few
hours ... from Earth starting straight up a slow speeds minimizes the
distance through the thick atmosphere and uses less fuel.
Thankfully on Vesta there is no air resistance to worry about, so a
sideways blast like we see in ejecta patterns would work as a fine
launch. What kills a Llama on Earth might be what makes a Moon of Vesta
;-)
Best wishes
Doug
-----Original Message-----
From: MexicoDoug <mexicodoug at aim.com>
To: sterling_k_webb at sbcglobal.net; rickmont at earthlink.net;
baalke at zagami.jpl.nasa.gov; meteorite-list at meteoritecentral.com
Sent: Fri, Jul 8, 2011 12:53 am
Subject: Re: [meteorite-list] Does Asteroid Vesta Have a Moon?
Hi Sterling,
For your run of the mill asteroid and some random impact, that would be
a pretty good summary ...
But personally, I think in the case of Vesta is anything but run of the
mill (i.e., commonplace) - anything could be possible.
I think, whether a Moon is found or not, the answer to Richard's
question regarding possibility could be figured out by looking at the
ejecta pattern and size distribution. You may be right about the
possibilities and you severely limit the case by supposing a 5 km size
giant rock. I want to generalize this more - the article we commented
on tenderly referred to the Dawn Spacecraft becoming a moon of Vesta -
so in that spirit we are talking about a 2 meter diameter one ton cube
with Solar Panels and antenna.
Thinking about the Meteor Crater or even bridging it to Carancas (see
the picture of the tossed bedmud ;-) )
e.g., Svend's first picture:
http://www.meteorite-recon.com/en/meteorite_carancas.htm
Could one such boulder fall into the correct velocity range as you
radiate outwards from the point of impact? Well, what is that velocity
range?
Well, Sterling: you gave us the escape velocity, but that is only one
point. To better answer the question, we need to know the range.
As you mentioned, the escape velocity is 350 m/s, so it would be less:
but how much less to get our arms around this beast? I'll spare the
calculation, all you need to do is divide 350 by square root of 2 to
get the minimum velocity to attain orbit around Vest's surface. So it's
247 m/s. Thus the range of upward velocity (in is 247 to 350 m/s for
Vesta. That's a big chunk of range. In English units 552 mph to 783 mph
(cruising speeds for commercial airliners up to about Mach 1).
You say:
"Only "close" moons are likely to be "chips off the old block."
I disagree with this too: since I don't see a reason that a 247 - 275
m/s velocity would be favored for example over 275 - 350 m/s in one of
these events, but I suppose if you want to focus on the range close to
escape velocity you could argue that point well ... and that more
distant captures are more likely statistically so I'll leave that one
alone since we are now talking about comparing two probabilities we
don't know anything much about.
It happens that the 247 - 350 m/s velocity range to launch from and
orbit Vesta is right at the middle of the muzzle velocities of a the
common .22 caliber rifle (which would make Vesta the ideal cartoon
world to shoot bullets in ellipses and have them go around and put a
hole in the back of the shooter's head.)
Do I think a small chunk could be ejected and go into orbit? ===> Most
definitely. Do I know the probability? No. Do I think piles of rubble
in the 247 - 350 m/s range could have been ejected - yes. Could it have
been hot from impact? Yes, hypothetically. Would it form a body - Maybe
not, I don't know. But if Carancas and Meteor Crater are any indication
I would think it wasn't as poor odds as your post might lead one to
believe whether you believe in chunks or rubble piles. Especially
considering there were a great deal more of kg's ejected from Vesta in
that impact. It's thought 1% of the Asteroid's mass, which comes out to
2,500,000,000,000,000,000 kg. Could 1000 of them be included? Sure!
Could anything a lot bigger be ejected in that velocity range. I dunno
but there are many tons of mass to play with in different impact
scenarios in a crater half the size of Germany.
Kindest wishes
Doug
Think Meteor Crater
-----Original Message-----
From: Sterling K. Webb <sterling_k_webb at sbcglobal.net>
To: Richard Montgomery <rickmont at earthlink.net>; Ron Baalke
<baalke at zagami.jpl.nasa.gov>; Meteorite Mailing List
<meteorite-list at meteoritecentral.com>
Sent: Thu, Jul 7, 2011 10:54 pm
Subject: Re: [meteorite-list] Does Asteroid Vesta Have a Moon?
Given Vesta's relatively low gravity -- 0.022 gee --
and its low escape velocity -- 350 m/s -- it would
be very heard to smash Vesta hard enough to knock
a chunk, oh, say, 5 km across off that hard rock
and yet have it have so little energy that it moved
slower than 350 m/s, which is a mere 783 mph.
Much more likely scenario of a "moon" is a capture
of a totally unrelated space rock. Lots of origin
theory smoke, no data measurement fire. That
is, we don't know the compositions of the minor
planet moons we do know about, and we do know
about quite a few:
http://en.wikipedia.org/wiki/Minor_planet_moon
Only "close" moons are likely to be "chips off the
old block."
Sterling K. Webb
---------------------------------------------------------------------
----- Original Message ----- From: "Richard Montgomery"
<rickmont at earthlink.net>
To: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>; "Meteorite Mailing List"
<meteorite-list at meteoritecentral.com>
Sent: Thursday, July 07, 2011 8:09 PM
Subject: Re: [meteorite-list] Does Asteroid Vesta Have a Moon?
> 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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