Itokawa is an S-type asteroid
that is around 1,800 feet long and around 700 - 1,000 feet wide.
This sequence was followed immediately with images of the nearby S-type asteroid
(755) Quintilla using the same sequence of filters, so that the relative intensity of the two objects could be directly compared.
These studies suggest that the small body--only 2,100 feet (640 meters) long--is an S-type asteroid
with a rocky composition.
Eros is an S-type asteroid
, meaning either that it may consist of primitive rocky material largely unchanged from early in solar-system history or that it melted to produce distinct layers of rock and metal.
are one of the most common objects in the asteroid belt," says Bose.
Many of the asteroids we've examined close up have been of just one type--the so-called S-type asteroids
(S stands for silicaceous).
are of a stony composition, and Itokawa is often referred to as a "rubble pile" due to the boulders, rocks and dust all stuck together by gravity (and possibly van der Waals forces).
Most asteroid specialists suspect that S-type asteroids
have undergone some kind of "space weathering," a catchall term applied to the various processes that might somehow transform the surfaces of ordinary chondrite asteroids into ones with S-type spectra.
Although its disk was not resolved, Masursky's reflectivity suggests that it may not be an S-type (stony) asteroid, as had been assumed based on its orbital association with the Eunomia family of S-type asteroids
. It was named for renowned planetary geologist Harold Masursky (1923-90).
They found that the inner asteroid belt is dominated by S-type asteroids
. The minor planets 951 Gaspra and 243 Ida, studied by Galileo in 1991 and 1993, respectively, are S types, as is 433 Eros.
Spectroscopically, S-type asteroids
bear some resemblance to the meteorite varieties called ordinary chondrites and stony-irons, both of which contain the silicate minerals pyroxene and olivine as well as iron.
Carlson, who heads the NIMS team, the object consists of roughly the same material as Ida itself, with a moderately reflective rocky composition common to S-type asteroids
. "We know for sure it's not an interloper," says imaging-team leader Michael J.