Jordan Willcocks, of Balclutha School, asks :-

Does Mars have any moons?

Frank Andrews, then an astronomer educator at Wellington's Carter Observatory, responded.

Mars' two tiny moons, Phobos and Diemos, are very small, asteroid-size, bodies which were discovered by Asaph Hall in 1877 at the US Naval Observatory in Washington. Phobos is the larger at 27 by 19km, while Deimos is 12 by 8 km. Phobos orbits Mars in 30 hours, while Deimos zips around the planet in only 7 hours 40 minutes.

Astronomers think that Deimos and Phobos are asteroids that were captured by Mars at some time in the distant past. It is probably just a matter of chance that Mars has only two moons. The giant planets like Saturn and Jupiter have a large number of moons, some of which are almost certainly captured asteroids. Presumeably, being much larger than Mars, they were able to capture a larger share of these small bodies.

If you use the internet the latest information about Mars is at http://pds.jpl.nasa.gov/planets/welcome/mars.htm For any other planet replace mars with its name.

Small moons orbiting the large planets are being discovered quite frequently. Jupiter had 11 tiny new moons added to its list only a few years ago.