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253 Mathilde

253 Mathilde

NASA image.
Orbital characteristics
Orbit type Main belt
Semimajor axis 2.64724 AU
Eccentricity 0.26522
Orbital period 4.31 years
Inclination 6.70777°
Physical characteristics
Diameter 66×48×46 km
Mass 1.033×1017 kg
Density 1.3 g/cm3
Rotation period 17d 9h 30m
Spectral class C
Albedo 0.04
Discoverer Johann Palisa, 1885

253 Mathilde (asteroid 253) was visited by the NEAR Shoemaker spacecraft on its way to 433 Eros. It is a primitive C-type asteroid, the first such asteroid to be visited by a spacecraft. It is also the largest asteroid to be visited by a spacecraft.

Mathilde is very dark, blacker than coal, and is thought to share the same composition as carbonaceous chondrite meteorites. The density measured by NEAR Shoemaker, 1.3 g/cm3 was less than half that of a typical carbonaceous chondrite; this may indicate that the asteroid is very loosely packed. The same is true of another C-type asteroid recently studied through ground-based telescopes, 45 Eugenia.

Mathilde's orbit is eccentric, taking it to the outer reaches of the main belt. It also has one of the slowest rotation periods of the known asteroids.

The asteroid is marked by a number of extremely large, extremely clear craters; several are wider than the asteroid's average radius.