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Hayabusa - The Return To Earth, The voyage home
Guest_BruceMoomaw_*
post Apr 30 2006, 02:35 PM
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It turns out that one of the new LPSC abstracts (#1575) by the Hayabusa team confirms that they think the lack of fine soil particles on Itokawa (as compared to Eros) is simply because of the asteroid's extremely low gravity: "Due to the low escape velocity of Itokawa (i.e., 10-20 cm/s), most of the fine ejecta in cratering having higher velocities
would have easily escaped from the surface. Only larger fragments with lower velocities than this escape velocity could have remained on the surface. This may explain why Itokawa’s surface has relatively small areas covered with regolith but is dominated by numerous exposed boulders."

This would presumably apply not only to ejecta directly kicked off by the surface by impacts, but to seismic shaking produced all over the asteroid by a large impact on it.

There is currently some belief that Itokawa's peculiar shape, which has been interpreted as being due to two rubble piles that collided with each other and stuck -- since any two such piles should have hit at such a high speed that they would have splattered and dispersed instead. Is it possible that Itokawa's shape -- a bifurcated lump, bent at the junction point -- is really just due to its being a single rubble pile that got a large impact on one side which splattered material away on that side and bent the entire pile?
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Bob Shaw
post Apr 30 2006, 03:48 PM
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QUOTE (BruceMoomaw @ Apr 30 2006, 03:35 PM) *
Is it possible that Itokawa's shape -- a bifurcated lump, bent at the junction point -- is really just due to its being a single rubble pile that got a large impact on one side which splattered mateial away on that side and bent the entire pile?


Bruce:

I wonder whether, over a very long period of time, a phenomenon similar to 'frost-heave' might occur - let's call it 'rubble creep'. Differential heating of rocks might lead to a verrrrrrry slow movement (perhaps after an impact gives everything a good shake) leading gradually to an ever-more deformed shape until some sort of equalisation of all the forces was reached.

If other rubble piles have the same sort of shape then it might be due to some such cause rather than a single event (I don't like single events, and much prefer long, slow processes!).

Bob Shaw


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Phil Stooke
post May 17 2006, 02:20 PM
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Upcoming symposium on Hayabusa...

http://kumano.u-aizu.ac.jp/hayabusa_symp2006/

Phil


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Shadowband
post May 31 2006, 11:25 PM
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JAXA Succeeded in Hayabusa Probe's Ion Engine Ingnition Test

JAXA succeeded in ion engine ignition test of Hayabusa probe,
which tried rock sampling from asteroid Itokawa. The acceleration
was fine. JAXA will start ion engines in next January and aim to
return to the Earth in June, 2010.

JAXA tried the test using two of four ion engines. "Return flight
is possible if two ion engines work", Dr. Jun'ichiro Kawaguchi
of ISAS/JAXA said.

From Mainichi Shimbun Press (in Japanese) 5-31-2006 19:07 JST
http://www.mainichi-msn.co.jp/science/kaga...040040000c.html
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helvick
post May 31 2006, 11:36 PM
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QUOTE (Shadowband @ Jun 1 2006, 12:25 AM) *
JAXA Succeeded in Hayabusa Probe's Ion Engine Ingnition Test

Now that's good news. Still rooting for " It is quick the ぶ". smile.gif
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Guest_AlexBlackwell_*
post Jun 1 2006, 02:14 AM
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Stay tuned tomorrow (June 1, 2006) for more Hayabusa science news biggrin.gif
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RogueEngineer
post Jun 1 2006, 02:31 PM
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QUOTE (Shadowband @ Jun 1 2006, 08:25 AM) *
JAXA Succeeded in Hayabusa Probe's Ion Engine Ingnition Test

And here's a official press release from JAXA:
Recent Status of Hayabusa spacecraft as of the end of May, 2006

Cheers,

Hideo Fukumori (aka Rogue Engineer)
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odave
post Jun 1 2006, 03:15 PM
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Great news! What a ride this must have been for the team, going from exhilaration to frustration to despair to guarded hopefulness. My hat is off to them for sticking with the mission in the face of severe adversity. Good luck in bringing the wounded Falcon home, guys smile.gif


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Guest_AlexBlackwell_*
post Jun 1 2006, 03:54 PM
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QUOTE (AlexBlackwell @ Jun 1 2006, 02:14 AM) *
Stay tuned tomorrow (June 1, 2006) for more Hayabusa science news biggrin.gif

What I was alluding to above was that the June 2, 2006, issue of Science is a special issue entitled "Hayabusa at Asteroid Itokawa."
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Guest_AlexBlackwell_*
post Jun 1 2006, 07:38 PM
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QUOTE (AlexBlackwell @ Jun 1 2006, 03:54 PM) *
What I was alluding to above was that the June 2, 2006, issue of Science is a special issue entitled "Hayabusa at Asteroid Itokawa."

Some related press releases:

Science team determines composition of asteroid Itokawa

Floating pile of rubble a pristine record of solar system's history

A sea otter-shaped rubble pile in space
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SigurRosFan
post Jun 1 2006, 07:47 PM
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... and:

- Rubbly Itokawa revealed as 'impossible' asteroid

<< Nonetheless, Hayabusa's cameras reveal that some large boulders appear layered, "like you'd broken off a rock from the side of a river bed," he says. That suggests Itokawa's parent body was large enough to heat up at its centre and develop some internal structure, even if it wasn't large enough to melt. "There could have been hydrothermal processes conducting water around, similar to on Earth, where steam passes through rocks and alters their compositions," he told New Scientist. >>


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ljk4-1
post Jun 1 2006, 07:48 PM
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Why we need to explore space directly.

A quote from the previously posted article:

What they found was completely unexpected. "Five years ago, we thought that we would see a big chunk of monolithic rock, that something so small doesn't have the ability to hold onto any pieces," says Erik Asphaug, a planetary scientist at the University of California in Santa Cruz, US, who is not involved with the mission. "Everything we suspected about it turned out to be wrong."


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"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Guest_AlexBlackwell_*
post Jun 1 2006, 08:38 PM
Post #133





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QUOTE (AlexBlackwell @ Jun 1 2006, 03:54 PM) *
What I was alluding to above was that the June 2, 2006, issue of Science is a special issue entitled "Hayabusa at Asteroid Itokawa."

For those of you with online access to Science, the papers are now available for download.
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Phil Stooke
post Jun 1 2006, 08:54 PM
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I played around with Hayabusa images last year, and made this map file. I didn't post it at the time, to let the mission scientists publish something first. I think it's OK now. And I want to emphasize this is VERY approximate and poorly controlled. But it gives an indication of what a simple cylindrical projection global photomosaic of Hayabusa would look like. IAU north is at the top. The "head" is at the central (0) meridian. This would not be suitable for any scientific analysis.

Phil

Attached Image


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dilo
post Jun 1 2006, 09:19 PM
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WOW, Phil! ohmy.gif
(and thanks, Alex)


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