Dawn departs Vesta to become first asteroid hopper

Jacob Aron, reporter

Postcard of Vesta from Dawn (Image:

A chunk of grey rock 525 kilometres wide, the asteroid Vesta is nice for a visit but you wouldn't want to live there. Having learned as much as it could from a year-long survey, NASA's Dawn probe is now departing Vesta for Ceres, the largest asteroid in the solar system (so big, in fact, that these days Ceres is also classed as a dwarf planet).

This will make Dawn the first ever asteroid-hopping spacecraft - a capability that could help pave the way for refuelling stations dotted throughout space and aid futuristic plans to send human explorers to an asteroid.

Dawn was launched on 27 September 2007 and flew 2.7 billion kilometres to reach the orbit of Vesta on 16 July last year, sending images and other scientific data back to Earth to help answer questions about how the early solar system formed. Yesterday it left Vesta's orbit and will travel a further 1.5 billion kilometres to reach Ceres in 2015.

The probe is able to make the "hop" from one asteroid to another thanks to its ion thruster engine, which uses electricity to accelerate xenon ions and then spit them out. This creates similar thrust to a conventional rocket but uses just one-tenth of the fuel.

Dawn's asteroid-hopping demonstration could prove useful to Planetary Resources of Seattle, which earlier this year declared its intentions to mine asteroids. First the company plans to send asteroid-spotting craft into Earth orbit. Then some of the probes will go on to the asteroids themselves to assess their potential value closer-up. Some will look for minerals, but discovering water on an asteroid could allow it to be used as a refuelling station as part of a longer mission to Mars. This would require landing on an asteroid, and then taking off - a bigger feat than Dawn's accomplishment, which involved merely entering and leaving an orbit. Still, it is a first step towards this goal.

More generally, understanding more about sending spacecraft to visit asteroids could also assist with a future crewed mission to a space rock. In 2010, US president Barack Obama announced NASA plans for humans to land on an asteroid as early as 2025.

Source: http://feeds.newscientist.com/c/749/f/10897/s/2325a983/l/0L0Snewscientist0N0Cblogs0Cshortsharpscience0C20A120C0A90Casteroid0Ehopping0Espacecraft0Ema0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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