Phobos

One of the two moons of Mars, discovered in 1877 by the US astronomer Asaph Hall. It is an irregularly shaped lump of rock, cratered by meteorite impacts. Phobos is 27 × 22 × 19 km/17 × 13 × 12 mi in size, and orbits Mars every 0.32 days at a distance of 9,400 km/5,840 mi from the planet's centre. It is thought to be an asteroid captured by Mars's gravity.

Phobos is named after a son of Ares and Aphrodite from Greek mythology. Phobos has been photographed by three separate probes – Mariner 9 in 1971, Viking 1 in 1977, and Phobos in 1988. A Russian probe called Phobos-Grunt is scheduled to be launched toward Phobos in 2009. (‘Grunt’ means ‘ground’ – the probe will return a Phobos soil sample.)

Phobos

Either of two Soviet spacecraft launched towards Mars in July 1988 to land on Phobos, one of the planet's two moons. Communication was lost with Phobos 1 before it reached Mars. Phobos 2 went into orbit around Mars in January 1989 but contact was lost on 27 March when it had approached to within 800 km/497 mi of Phobos.