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Wednesday, 26 September, 2001, 09:45 GMT 10:45 UK
Q&A: Comet Borrelly images

The American space agency, Nasa, has published astonishing pictures of Comet Borrelly's nucleus, taken by the unmanned spacecraft Deep Space 1.

The mission's director, Dr Marc Rayman, has himself described the images as stunning. The BBC asked him what the new close-up pictures tell us about the nature of comets.

A: The data are so new that it's too soon to draw conclusions, but comets previously were just very, very mysterious, and now we have enough information to start putting together the pieces of a puzzle that will tell us about the nature of comets and therefore the origin and evolution of the Solar System and Earth, and perhaps even life on Earth.

DS1 Nasa/JPL
The DS1 images reveal different types of terrain
What have we learnt about the kind of terrain, the landscape, on these objects?

A: Well, indeed, prior to DS1's encounter with Comet Borrelly, we had a set of beautiful images of Comet Halley from the Giotto spacecraft. But they weren't clear enough actually to see any terrain on the comet, and now we can see not only terrain, but several different kinds of terrain.

There are plains, and maces, and jumbled rough areas and flat areas, and we can see areas that are producing high-velocity jets of material, and so it's really like, literally, a whole new world to explore.

Giotto's image of Comet Halley showed us little of the surface of the nucleus
So, why haven't we had images like this before now? What's been the difficulty?

A: There are several difficulties. One is that it's simply very difficult to get spacecraft to comets. They have orbits which make them difficult to reach, and they present very, very challenging and difficult environments to penetrate, and, in fact, on DS1, I actually did not have high confidence that the spacecraft would survive its passage by the comet.

In addition, it's only been recently that the full scientific importance of comets has begun to be appreciated, and that then has led to a renewed interest in comet missions.

So what, just to sum up, would you say is their importance?

A: Well, comets are like time capsules. They contain remnants from the formation of the Solar System. They have the materials and the conditions of the time the Solar System was formed preserved in them, and so by studying them, we can learn much more about the Solar System and again life on Earth - perhaps.

Dr Marc Rayman
Only recently has the full scientific importance of comets been appreciated
See also:

25 Sep 01 | Sci/Tech
'Stupendous' comet pictures revealed
21 Sep 01 | Sci/Tech
Countdown to comet encounter
20 Sep 01 | Sci/Tech
Spaceprobe set for comet encounter
27 May 01 | Sci/Tech
Nasa to crash probe into comet
08 Aug 00 | Sci/Tech
Hubble finds missing comet pieces
05 Apr 00 | Sci/Tech
Longest comet tail detected
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