Astronomy Picture of the Day -- The Missing Craters of Asteroid Itokawa

NASA ^ | February 09, 2014 | (see photo credit)

[SunkenCiv]

Explanation: Where are the craters on asteroid Itokawa? Missing -- unexpectedly. The Japanese robot probe Hayabusa approached the Earth-crossing asteroid in 2005 and returned pictures showing a surface unlike any other Solar System body yet photographed -- a surface possibly devoid of craters. The leading hypothesis for the lack of common circular indentations is that asteroid Itokawa is a rubble pile -- a bunch of rocks and ice chunks only loosely held together by a small amount of gravity. If so, craters might not form so easily -- or be filled in whenever the asteroid gets jiggled by a passing planet or struck by a massive meteor. Recent Earth-based observations of asteroid Itokawa have shown that one part of the interior even has a higher average interior density than the other part, another unexpected discovery. The Hayabusa mission returned soil samples from Itokawa which are also giving clues the ancient history of the unusual asteroid and our entire Solar System.

[SunkenCiv]

[Credit & Copyright: ISAS, JAXA]

[SunkenCiv]

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The Big One

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[FlingWingFlyer]

That’s strange. Thanks for the post.

[bmwcyle]

Rock of Ages.

[Telepathic Intruder]

Probably recently broken apart and then reformed. When a potato starts looking that bad, do you throw it out or make soup?

[Triple]

Does it melt and re-freeze?

[Chode]

[SunkenCiv]

This article reiterates the 'rubble pile' explanation, but notes that one end is lower density than the other. That could be suggestive of water ice. My view is that all the Earth-crossers formerly were part of now-extinct comets.

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KEYWORDS: asteroid; asteroiditokawa; hayabusa; itokawa

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[Chode]

that's a valid explanation

[Telepathic Intruder]

That’s interesting, actually. Then they’re constantly being replenished even with the occasional Tunguska event. There’s just a tiny whisper of gravity holding asteroids together, however. Low density does not necessarily imply light elements.

[shibumi]

[RedMDer]

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[SunkenCiv]

An Asteroid, Cobbled Together
ScienceNOW Daily News | 2 June 2006 | Phil Berardelli
Posted on 6/3/2006 3:34:15 AM by neverdem
http://www.freerepublic.com/focus/news/1642717/posts

[SunkenCiv]

Quite right, there could be voids in the less dense part, much as there may be in one of Mars’ moons.

[Chode]

gravity surly works on all things

[TigersEye]

It will go good with the Sour Cream Belt of the Milky Way.

[Mr. K]

"The Hayabusa mission returned soil samples from Itokawa"

huh? thats a pretty big deal- why wasn't I notified?

[Telepathic Intruder]

Haven’t heard that. Deimos I assume?

[Swordmaker]

This article reiterates the 'rubble pile' explanation, but notes that one end is lower density than the other. That could be suggestive of water ice. My view is that all the Earth-crossers formerly were part of now-extinct comets.

Unfortunately for your theory, every comet we've analyzed or visited has shown essentially zero water. . . and is indistinguishable from any other asteroid except for orbit and electrical charge.

[SunkenCiv]

The Anatomy of an Asteroid