Pallas is the third-largest asteroid, found in 1802 by Olbers while he was following the newly discovered Ceres. Its orbit is tilted almost 35° to the plane of the planets, so it plunges through the asteroid belt at steep angles - and its heavily cratered surface, battered like a golf ball, shows the violent consequences.
Its orbit is inclined nearly 35° - by far the steepest of the large asteroids.
It was the second asteroid ever discovered, and for decades was counted as a planet.
It is the largest asteroid that no spacecraft has ever visited.
An orbit that keeps visitors away
Spacecraft ride the ecliptic - the flat plane where the planets orbit - because changing orbital planes costs enormous amounts of fuel. Pallas spends most of its time far above or below that plane, which is why the third-largest asteroid has never had a visitor while smaller, better-placed bodies have been orbited, sampled and landed on.
Physical characteristics
Diameter
512 km
Mass
2.000e+20 kg
Density
2.9 g/cm³
Rotation period
7.81 h
Geometric albedo
0.16
Atmosphere and composition
Atmosphere
None.
Composition
B-type: dark, water-altered silicate rock, similar to carbonaceous chondrite meteorites.