Article: Strange Asteroid Shapes Explained

Selections from the article...

Researchers have been using a vast database to study a staggering 11,735 asteroids. They have discovered that asteroids change shape over time, and they think they know the reason why.

Gyula Szabó from the University of Szeged [Hungary] is the lead author of the study, which was published in the July edition of Icarus. He explains, "There are several hundred thousand asteroids in our solar system. They orbit the sun, but because they are small their surface gravity is low. This means that many have strange, irregular shapes."

Scientists like Gyula think that about one third of known asteroids belong to groups called "families." These clusters probably formed from piles of debris after larger objects collided.

But what changes the asteroids' shape? Gyula and his team have shown that asteroids change shape from elongated to roughly spherical due to being impacted during their lifetimes. They are like pebbles on the beach that become worn smooth over many years -- only in space, erosion is caused by small impacts as rocks knock into each other and chip pieces off.

"Strange Asteroid Shapes Explained"
Lee Pullen
Astrobiology Magazine
03 July 2008

Link: Space.com article

---- ICARUS ABSTRACT

"The shape distribution of asteroid families: Evidence for evolution driven by small impacts"

Gyula M. Szabóa, b, Corresponding Author Contact Information, E-mail The Corresponding Author and László L. Kissc

aMagyary Fellow, School of Physics A28, University of Sydney, NSW 2006, Australia

bDepartment of Experimental Physics, University of Szeged, 6720 Szeged, Hungary

cSchool of Physics A28, University of Sydney, NSW 2006, Australia

Received 17 July 2007;
revised 22 November 2007.
Available online 29 February 2008.

Abstract

A statistical analysis of brightness variability of asteroids reveals how their shapes evolve from elongated to rough spheroidal forms, presumably driven by impact-related phenomena. Based on the Sloan Digital Sky Survey Moving Object Catalog, we determined the shape distribution of 11,735 asteroids, with special emphasis on eight prominent asteroid families. In young families, asteroids have a wide range of shape elongations, implying fragmentation–formation. In older families we see an increasing number of rough spheroids, in agreement with the predictions of an impact-driven evolution. Old families also contain a group of moderately elongated members, which we suggest correspond to higher-density, more impact-resistant cores of former fragmented asteroids that have undergone slow shape erosion. A few percent of asteroids have very elongated shapes, and can either be young fragments or tidally reshaped bodies. Our results confirm that the majority of asteroids are gravitationally bound “rubble piles.”

Link: ICARUS Abstract