M-type asteroid

M-type asteroids are metallic asteroids; they are moderately bright (albedo .10-.18) and made of nickel-iron, either pure or mixed with stone. They are thought to be samples of the metallic core of differentiated asteroids that were fragmented in the early history of the Solar system by impacts, and originate in the inner portion of the asteroid belt. This type is the third-most abundant in the asteroid belt, and is thought to be the source of iron and stony iron meteorites.

Their spectrum is flat to reddish and usually devoid of large features, although subtle absorption features longward of 0.75 μm and shortward of 0.55 μm are sometimes present.

16 Psyche is the largest M-type asteroid. 21 Lutetia will be the first M-type asteroid to be imaged by a spacecraft when the Rosetta space probe visits it on July 10, 2010. Another M-type, 216 Kleopatra, was the first main belt asteroid to be imaged by radar by the Arecibo Observatory in Puerto Rico.

You can use the "What links here" toolbox link to find more asteroids of this type.

References

1. S. J. Bus and R. P. Binzel Phase II of the Small Main-belt Asteroid Spectroscopy Survey: A feature-based taxonomy, Icarus, Vol. 158, pp. 146 (2002).