| Asteroids
are rocky and metallic objects that orbit the Sun but are too small to
be considered planets. They are known as minor planets. Asteroids range
in size from Ceres, which has a diameter of about 1000 km, down to the
size of pebbles. Sixteen asteroids have a diameter of 240 km or greater.
They have been found inside Earth's orbit to beyond Saturn's orbit. Most,
however, are contained within a main belt that exists between the orbits
of Mars and Jupiter. Some have orbits that cross Earth's path and some
have even hit the Earth in times past. Asteroids are material left over
from the formation of the solar system. One theory suggests that they are
the remains of a planet that was destroyed in a massive collision long
ago. More likely, asteroids are material that never coalesced into a planet. |
The
Asteriod Gaspra
The
Galileo spacecraft flew past Gaspra in October 1991 During these encounters,
high resolution images were obtained. (photo NASA)
|
