Image asteroid


Ida, one of the 5000 known asteroids, is represented in the figure. It is a huge, bare, potato-shaped rock with elevations and long fractures present on its surface.

Asteroids, Ida included, are small, rocky, desert-like bodies of widely varying dimensions. These bodies range in size from a few hundred kilometres to thousands of kilometres. One of the largest is Ceres, which is today classified as a dwarf planet. Asteroids are also known as planetoids.

The total mass of all known asteroids is not as large as that of the Moon.

There are over 5000 known asteroids but there are also many unknown ones, either because they are too small or because they have not been catalogued. The majority of asteroids orbit in a belt between the orbits of Mars and Jupiter.

The origin of the asteroids is still not very clear. It is thought that they are the remaining chunks of a planet that should have been formed between Mars and Jupiter: according to this theory, Jupiter’s enormous gravitational pull was not sufficient to trap them but it did manage to stop them grouping together, which would have resulted in the formation of a new planet.

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