3 min read

All in the Family: Scientists Find Mother and Daughter Asteroids

Geological Society of America
Boulder, Colorado

Ann Cairns, Director of Communications and Marketing
acairns@geosociety.org, 303-357-1056

Written by Kara LeBeau, GSA Staff Writer

GSA Release No. 01-59

There are asteroids and there are asteroids. Most were once part of larger "parent bodies" and some supply meteorites that plunge to Earth.

But how do you trace the family line of asteroids? Scientists compare mineralogy of asteroids by analyzing their near-infrared spectra. They also compare asteroids' orbits around the sun. And recently they found a perfect match - "uniting" in a scientific sense, mother and daughter asteroids.

"We determined the mineralogy of asteroid 1929 Kollaa and found that it was once part of a larger asteroid called 4 Vesta. I was inspired to observe these objects because they belong to the rare V-class of asteroids, and they have orbits about the Sun that are very similar," explained Michael Kelley from NASA's Johnson Space Center. "Vesta is the asteroid for which the V-class was established. Until now, no mineralogical analysis had ever been done on another V-type. In that sense, Vesta was unique until our recent work was done. We found not only that this second V-class asteroid, 1929 Kollaa, was once part of Vesta, but that it is also related to a very specific group of meteorites."

Kelley will present this new discovery on Thursday, November 8, at the Geological Society of America's annual meeting in Boston.

Most planetary scientists believe that 4 Vesta is the source of howardite, eucrite, and diogenite meteorites (HED) found on Earth, but Kelley points out that it is not a direct process. "Vesta is located in a part of the main asteroid belt that makes it almost impossible for it to deliver meteorites directly to Earth. So there are probably intermediate asteroids, which were once part of Vesta, located in more favorable orbits that provide delivery."

One of the ramifications of this discovery is that it will help scientists build a geologic map of the asteroid belt and understand what forces have acted on asteroids in the past. This information, along with asteroids' mineralogy, would be crucial if there was ever a need to prevent an asteroid from striking the Earth and causing a major disaster.


During the GSA Annual Meeting, November 4-8, contact Ann Cairns or Christa Stratton at the GSA Newsroom in the Hynes Convention Center, Boston, Massachusetts, for assistance and to arrange for interviews: (617) 954-3214.

The abstract for this presentation is available at:

Post-meeting contact information:

Michael S. Kelley
NASA Johnson Space Center
Code SR
2101 NASA Rd. 1
Houston, TX 77058
E-mail: michael.kelley1@jsc.nasa.gov
Phone: 281-244-5119
Fax: 281-483-1573

Ann Cairns
Director of Communications
Geological Society of America
Phone: 303-357-1056
Fax: 303-357-1074
E-mail: acairns@geosociety.org