Stardust Published

This morning the Italian newspapers all seem to have Stardust on their front pages - even the free ones! I thought there must be big news and I asked my Italian colleague to tell me what had happened. He tells me that the reporters are claiming that new results "prove" that we are all made of star dust. Although I thought this was likely to be reporter's hyperbole, the first thing I did when I got to work was to find out what has actually been announced.

You may remember that the Stardust mission to Comet Wild 2 was launched back in February 1999. I remember it because it was the first mission I was aware of that took a CD of names with it. As you can imagine, I added most of my family and friends to it. At the start of 2004 Stardust caught up with the Wild 2 and returned some images. It also exposed one side of an aerogel tile to the shower of particles streaming from the comet. As the comet originates out in the Kuiper belt, it was hoped that some of these small flecks of dust may originate from a time before the start of our solar system and so shed light on what conditions were like before the Sun "turned on". Stardust was also the first mission to return solid samples from another solar system body since the Apollo missions.

The reason for the sudden interest by the newspapers and TV is that today's Science Express has a special series of articles about Stardust (and there is a press release from JPL in case you need a subscription for Science) in which the preliminary science results from the mission are published. So what exactly has got the Italians (and the BBC) so excited? The news that seems to have made the press is the discovery of organic molecules (Science 15 December 2006: Vol. 314. no. 5806, pp. 1720 - 1724). Of course, organic molecules have been discovered in many different places in space and, rather than referring to life, the term 'organic' means that the molecule contains carbon and hydrogen. It's still quite exciting though.

The organic molecules that they've found are similar to those in interplanetary dust grains and carbonaceous meteorites, although they seem to have more nitrogen and oxygen. This suggests that the molecules brought back from Wild 2 are not the result of ejecta from stars or even chemical processes in the diffuse medium between stars but they are consistent with ices being heated by radiation in a dense cloud such as that surrounding our Sun when it was just a proto-star. The ratios of oxygen to carbon and nitrogen to carbon are also higher than for meteorites and even those seen by the Giotto spacecraft at Comet Halley. The paper suggests that it may be a new class of organic molecules not previously seen in extraterrestrial samples.

The cometary dust samples also contain some minerals that could only have formed at high temperatures. This is surprising because the comet originates in the outer solar system yet these minerals seem to have come from the inner solar system. The Stardust team suggest that this may infer large flows of material in the very early solar system outwards from the Sun.

So lots of results there and I don't have time just now to read the rest of the papers they published. But this is just the end of the preliminary phase and the in-depth science is actually only just beginning. Not only is there is still a possibility for Stardust and Deep Impact to visit further comets, but results from the other side of the aerogel (exposed to interstellar dust) are still to appear. Expect much more science from Stardust in the future.

Posted in astro blog by Stuart on Friday 15th Dec 2006 (10:43 CET) | Permalink
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