NASA has is to send a probe on a collision course with a comet's nucleus to find out more about the composition and history of the bodies.
The mission, dubbed "Deep Impact", launches from Florida on 12 January and will arrive at its destination, the comet Tempel 1, six months later, on 4 July. It will then deploy a probe - a 360kg, metre-long, cylindrical projectile - that will collide with the comet at around 37,000 kph.
Scientists hope that the space craft will create a crater in the surface of the comet, and so allow them a glimpse of the interior. It is possible, however, that the probe will merely be destroyed on impact (it is designed to be) without damaging the comet at all.
The probe will carry a camera to capture images of the comet's surface as it approaches, but the mothership will be nearby, recording events.
"We will be capturing the whole thing on the most powerful camera to fly in deep space," said Dr. Michael A'Hearn, Deep Impact's principal investigator and astronomy professor at the University of Maryland. "We know so little about the structure of cometary nuclei that we need exceptional equipment to ensure that we capture the event, whatever the details of the impact turn out to be."
Deep Impact follows the launch of the European Space Agency's Rosetta mission. This mission aims to land on the surface of a comet and conduct a number of experiments, including analysis of the composition of the comet, and the interaction of the comet with the solar wind.
NASA's mission was originally scheduled to launch this month, but an equipment review found some faults that needed correction. It is schedule to depart on 12 January, but the launch window lasts a bit longer, and the mission will be able to go ahead up until 28 January. ®