BioEd Online

NASA is readying to send a speedy craft out to the edges of our Solar System, to give us our first ever close-up of Pluto.

The New Horizons mission, which is due to launch from Florida on 17 January, will zoom past the Moon in just nine hours, travelling at a speed nearly 100 times that of a jet plane. The piano-sized craft is then scheduled to swing past Jupiter in 2007 picking up a gravity 'sling-shot' that will speed up its travel to Pluto. If all goes according to plan, the craft should reach Pluto by mid-2015.

The smallest planet in our Solar System, Pluto is the only one that has not yet been visited by a spacecraft (see Box). It is located at the outermost zone of the Solar System, known as the Kuiper belt. Here a series of comets and icy planetary objects left over from the birth of the Solar System reside.

Pluto has been the subject of a great debate: is it a planet, or simply a large object that belongs to the Kuiper belt? New Horizons might help to shed light on this philosophical question by finding out a little more about the object. The mission should help to determine whether it has an atmosphere, for example, and whether it is completely round or is mis-shapen.

The mission has suffered several setbacks on its way to launch, thanks to noise-plagued instruments and production delays. But now things look set to go. In order to get a boost by sling-shotting around Jupiter, the craft needs to be launched by 3 February. Later launch dates will see it miss this opportunity, pushing its arrival at Pluto back by years.

Low energy

The craft has been designed to run on low power for most of its long haul. Once it passes Jupiter, a modest power input equivalent to that needed to run two light bulbs will keep critical instruments on and will run yearly system check-ups. Otherwise it will be 'asleep' for the remainder of the trip. "It's sort of like being on a long stretch of countryside road on a long bus tour," said co-investigator Ralph McNutt Jr, of Johns Hopkins Applied Physics lab where the craft was designed and built.

Once New Horizons reaches its goal of Pluto, a host of instruments will power up, says McNutt. The small craft is packed with imaging infrared and ultraviolet spectrometers, a multicolour camera, a long-range telescopic camera, two particle spectrometers and a University of Colorado at Boulder student-designed space-dust collector.

These instruments will look at things such as the effects of the solar wind on Pluto and determine the presence and composition of Pluto's atmosphere.

Bang for your buck

In recent years Pluto and its neighbourhood have unfolded a series of surprises. In 2001, astronomers discovered a number of other systems similar to Pluto and its moon in the Kuiper belt. And in 2005, two extra moons were found around Pluto. Because New Horizons was originally designed just to look at Pluto and its single known moon Charon, project scientist Hal Weaver notes that they will be able to "look at four for the price of two".

"In a sense, it was 'let's go see the oddball,'" says Mike Brown, a planetary scientist from the California Institute of Technology, about the original motivation to visit Pluto. "Now it's 'hey, it's not such an oddball'," he laughs. But that's even more reason to visit the outer edges of the Solar System, he adds.