Notable deep space missions currently exploring our farthest frontiers.

CASSINI-HUYGENS

A NASA mission with considerable European participation, it arrived in the Saturn system in 2004 and has sent back reams of data and spectacular images of our solar system's second largest planet, its moons and its famous rings. In fact, the moons Titan and Enceladus are primary targets of the mission and Cassini has hugely helped in improving our comprehension of these two prime candidates for finding traces of extraterrestrial life. The Huygens probe plunged into Titan's thick atmosphere and found, among other things, a new world of vast methane lakes and seas. Cassini is scheduled to finally plunge into Saturn in 2017.

DAWN

The Dawn spacecraft has two targets, Ceres, a dwarf planet in the asteroid belt between Mars and Jupiter, and Vesta, the largest asteroid. Both these bodies are considered to be the largest 'protoplanets' (which collided to form the planets of our solar system) that are still intact as their accretion into something bigger was prevented by Jupiter's massive gravitational pull. Dawn, launched in 2007, and currently in orbit around Vesta, will study 'the role of size and water content in determining the evolution of the planets'.

ROSETTA

A European Space Agency mission, Rosetta is the first one designed to orbit and land on a comet - with its Philae lander. The spacecraft carries 20 science instruments and will make a detailed study of comet 67P/Churyumov-Gerasimenko for two years as it approaches the sun. Scheduled to insert itself into orbit in 2014, the probe will be the most detailed mission ever to be launched to a comet and the information it generates will also help shed light on the formation of the solar system.

NEW HORIZONS

Launched in 2006, this ambitious NASA mission aims to enhance our understanding of the outer reaches of our solar system, and especially of Pluto - now a 'dwarf planet' after being downgraded in 2006. It is scheduled to arrive at Pluto in 2015. After a period of studying the dwarf planet, it will be pointed to other interesting objects found in the Kuiper Belt, a region of the solar system beyond Neptune. It is made up of scattered celestial objects (dwarf planes, icy 'volatiles' and asteroids) probably left over from the formation of the solar system.

VOYAGER

The two most famous deep space probes ever sent out, the Voyagers (I & II) were launched a month apart in 1977 and have probably done the most to further our understanding of the solar system. The probes flew past Jupiter and Saturn and then Uranus and Neptune, all the while transmitting mountains of data and historic images of these planets, 48 moons, planetary rings and magnetic fields. These hardy spacecraft are now poised to exit the solar system and beam back some data on whatever they encounter. At a distance of 120 'astronomical units', Voyager 1 is now the farthest human-made object from the sun.

PRAVEEN DASS