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ESA targets Mercury with BepiColombo mission

Joining forces with JAXA

The European Space Agency (ESA) has given the go ahead for a mission to explore Mercury, the inner-most planet of our solar system. The mission was formally adopted at the agency's Science Programme Committee (SPC) meeting last Friday.

BepiColombo is a joint mission between ESA and JAXA, the Japanese space agency. It will consist of two satellites, one for planetary investigations and the other for mapping the world's magnetic field.

It will travel using a combination of very low thrust and gravity assist, as demonstrated by the SMART-1 mission to the moon. The craft carrying the two probes will use the moon, Earth, and Venus to gain speed, as well as its own ion propulsion engine.

Japan is heading up the design and construction of the Mercury Magnetospheric Orbiter (MMO), while ESA has taken charge of the Mercury Planetary Orbiter (MPO). The MMO will carry five instruments, and the MPO will carry 11.

Both orbiters will be truly collaborative works: four of the five MMO instruments will be provided by Japan, but are likely to have European contributions to the technology. Russia will be providing one of the instruments for the planetary orbiter.

Although plenty of probes have been dispatched to Mars and Venus, relatively little is known about Mercury. Mariner 10 flew past the planet three times in 1974 and sent back images of just 45 per cent of its surface. It is a place of extremes: fiercely hot on the side facing the sun - it can reach 470°C on the surface - but bitterly cold on the dark side.

Beyond that, we know Mercury is the only planet aside from Earth with a global magnetic field, but little else.

Pressing as the need for new data is, scientists are not going to find out more for a while. BepiColumbo won't even leave Earth until 2014, and will arrive in orbit around Mercury in 2019.

Part of the reason for the long ramp up to launch is the difficulty of constructing instruments that can withstand the planet's extreme conditions. Not only is the planet baked by the sun's heat, it radiates that heat back into space as well, making orbit a hostile place.

Meanwhile, NASA's Messenger probe is heading towards the smallest planet, and will arrive in 2011. It is also set to study its composition, and map its surface and magnetic field. It will also investigate the possibility of ice deposits at the planet's poles. ®

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