[meteorite-list] Earth's 'Quasi-Moon' Is Wayward Asteroid (2003 YN107)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:53 2004
Message-ID: <200403251710.JAA27998_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99994814

Earth's 'quasi-moon' is wayward asteroid
David L Chandler
New Scientist
March 24, 2004

The Earth has only one true Moon, but astronomers have found that we also
have a "quasi-moon" - a travelling companion through space that is circling
the Earth while actually orbiting the Sun.

The object, the only quasi-moon discovered so far, is an asteroid called
2003 YN107 which circles the Sun in an orbit almost identical to Earth's,
but follows a corkscrew path that from time to time means that it appears to
orbit Earth.

Relative to Earth, the asteroid usually follows a horseshoe path that
sometimes lags behind us and is sometimes ahead. But since 1996 its path has
taken it round Earth, making it a quasi-satellite. This phase will last
until 2006.

The asteroid is probably a big chunk of debris from a lunar impact,
according to Paul Chodas, a specialist in asteroid orbits at NASA's Jet
Propulsion Laboratory in Pasadena, California. Chodas and his colleagues
reported the discovery at the Lunar and Planetary Science Conference in
Houston, Texas, last week.

Another object discovered two years ago, 2002 AA29, follows a horseshoe path
relative to Earth, but will not be a quasi-satellite again for 500 years.

A third asteroid, Cluithne, can also sometimes loop around the Earth. These
objects may be the first examples of a new family of asteroids, says Chodas.
They may also make suitable destinations for future space missions from
which samples might be brought back to Earth.
Received on Thu 25 Mar 2004 12:10:19 PM PST