TOPIC OF THE MONTH – ASTEROID BELT

BETWEEN Mars and Jupiter lies a unique region of our solar system containing a band of asteroids; rocks ranging from millimetres to miles in diameter all orbiting round the Sun in formation.

The total mass of all these asteroids is only about four per cent of that of the Moon and half of the total mass is contained within just four large asteroids. Although there are millions of separate asteroids in this region, unlike science fiction films often portray, the asteroids are in fact all very far from each other and many spacecraft have passed through the region without having to make any changes in trajectory.

In fact, although the orbits of larger asteroids are monitored and specifically avoided by space crafts, launches take no account of smaller asteroids and it’s just assumed space craft will have an extremely low chance of hitting one as they pass through the region.

Quite why the asteroids are there is unknown.

Possibly they formed at the same time as the rest of the planets from coalescing dust but were prevented from clumping together to form a small planet by the gravitational force from nearby Jupiter.

Not all the orbits of asteroids are completely regular and if they hit each other they can change course drastically and many hit planets causing the familiar craters we see.

NASA attempts to track the orbits of bigger ones, but it is a difficult job; there are estimated to be between 700,000 and 1.7 million asteroids each larger than one kilometre in diameter.