Scientists Find Migrating Regolith On Tiny Asteroid Itokawa

IRON AND ICE

Asteroid Itokawa.

by Staff Writers
Tokyo, Japan (SPX) Apr 22, 2007
Unprecedentedly high-resolution images from the Hayabusa spacecraft, the first Japanese asteroid mission, show unexpected evidence of the migration of gravels covering the surface of asteroid Itokawa.

Hirdy Miyamoto (an Affiliate Scientist of PSI and an Associate Professor of University of Tokyo), Bob Gaskell (a Senior Scientist of PSI), and others studied the Hayabusa's high-resolution images with up to 6mm/pixel resolution and discovered that Itokawa was covered with unconsolidated millimeter-sized and larger gravels. The finest granules are in pebble size and are found only in the smooth-looking terrains that cover 20% of the surface.

This is surprising because impact ejecta on a small asteroid is expected to spread globally over its surface resulting in continuous regolith. In a paper being published today in the journal Science, Miyamoto, Gaskell, and others propose that unconsolidated gravels have globally migrated and segregated due to fluidization caused by vibrations likely induced by impacts of small meteoroids.

The key morphological evidence for the gravel migration is how gravels align in very close-up images. The directions of the longest axes of gravels might be randomly distributed if they are simply accumulated. However, statistic analyses based on mapping of the gravels indicate that Itokawa's gravels are generally aligned.

Deposits of terrestrial riverbed or landslides often show similar alignments. The directions of these asteroidal gravel migrations exactly coincide with the directions of local gravitational slopes.

When gravel is vibrated, it can be fluidized and behave as granular fluid. The most popular phenomenon related to this is called the "Brazil nut effect"---the biggest particles end up on the surface when granular material is shaken. Thus, the stranding of boulders covering the rough terrain of Itokawa may have occurred as a result of this process. Granular processes may be a major resurfacing mechanism for all small asteroids possessing regolith.

The content of this story is covered by the following paper: Miyamoto, H., H. Yano, D.J. Scheeres, S. Abe, O. Barnouin-Jha, A.F. Cheng, H. Demura, R.W. Gaskell, N. Hirata, M. Ishiguro, T. Michikami, A. M. Nakamura, R. Nakamura, J. Saito, and S. Sasaki, Regolith Migration and Sorting on Asteroid Itokawa, published online 19 April on Science Express, 10.1126/science.1134390. http://www.sciencexpress.org

Email This Article

IRON AND ICE

Celestial Fender-Bender Left Asteroid To Cool Without Insulation

Amherst MA (SPX) Apr 20, 2007
A fender-bender between two celestial bodies that left a 200 mile-wide metallic chunk to cool in space was the likely source of a group of meteorites known as the IVA iron meteorites, suggests new research by University of Massachusetts Amherst scientists. Their findings, published in the April 19 issue of the journal Nature, help explain conflicting meteorite data that has long puzzled scientists, and sheds new light on how and when asteroids form.

SUPERPOWERS Abe Sees More Assertive Japan Across Entire World Russia Downbeat Ahead Of NATO Talks Royal Navy's Shame Chinese PM Seeks New Trust With Japan	NUKEWARS The INF Treaty Part Two Agni-III Challenge Facing Indian Military Doctrine US Welcomes North Korean Pledge On Nuclear Shutdown Pacific Nuclear Victims Awarded One Billion Dollars
MISSILE NEWS Skyguard AMOUN Scores Direct Hit In Live Missile Firing Using Raytheon-Upgraded Launcher India Dismisses Airline Complaints Over Missile Test Thailand Embark On Local Missile Program Lockheed Martin Demonstrates P44 Missile Performance And Agility	MISSILE DEFENSE Russia Rejects US Offer On Missile Shield US Releases Technical Details On Missile Shield In Central Europe Czech MPs Visit US Radar Base Earmarked For Missile Shield Oslo Clash On ABM
AEROSPACE Australia Fears Jet Flight Guilt Could Hit Tourism New FAA Oceanic Air Traffic System Designed By Lockheed Martin Fully Operational Nondestructive Testing Keeps Bagram Aircraft Flying NASA Seeks New Research Proposals	UAV NEWS Air Force Official Testifies On UAV Executive Agent Issue Boeing-Insitu ScanEagle UAV Logs 1000 Combat Flight Hours With Australian Army Maiden Flight Killer Bee UAV Global Hawk Lands An Industry First For A Goodrich Production Electric Braking System
IRAQ WARS Black Wednesday In Baghdad Suicide Bomb Attacks Present Top Challenge In Iraq US Wounded Rate Down Sharply Bush Seeks Cover On Iraq	MILTECH Battlefield Technology Key To Atlantic Strike V Seabees Build Modular Protected Billeting For Warfighters New Mission Control Room Ready For F-35 Flight Tests Osprey Aircraft To Take Off In Iraq

The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement