Astrophysicist Scott Sandford Discusses Stardust Preliminary Findings (Segment 2)

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Astrophysicist Scott Sandford Discusses Stardust Preliminary Findings (Segment 2)
03.28.07
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(Segment 2/Music begins)

Jesse Carpenter: Welcome to Part 2 of our podcast interview with Scott Sandford from the NASA Ames Research Center.

Tell us a little bit about the team who analyzed the samples.

Scott Sandford: We decided early on that the samples shouldn’t be examined just by the members of the Stardust team, but that we should put together a wider team of people from around the world who could bring a whole variety of analytical techniques to bear. And in the end, the preliminary examination team, I believe, had something on the order of 175 scientists on it from around the world. And I’m not sure the total number of institutions involved but it’s something like 70 or 80 institutions. I know on the organics paper for the organics team that I led I think the final paper had 55 authors from 31 institutions.

So while NASA certainly deserves huge credit for getting this mission together and paying the bill and getting it there successfully and all of that, the actual analysis of the sample has been opened up to the worldwide community -- I think to NASA’s credit -- and it’s been a real joint effort on the part of all these folks. And I anticipate in the future, as samples continue to be allocated beyond the Stardust mission, that we’ll see this same thing happening -- that we’ll see participating by people from all around the world. Scientists from many, many institutions will continue to look at this stuff in much the same way that people from all around the world are free to request lunar samples brought back by the Apollo astronauts, Antarctic meteorites found by ANSMET and so on.

Jesse Carpenter: How rare is it is for us to get something that’s this old?

Scott Sandford: Well, certainly there’s nothing on that belongs to the Earth that’s four and a half billion years old. Every rock on the Earth has been processed since the Earth formed. So there’s nothing that old that’s the Earth’s. Okay, but we do get things that are four and a half billion years old that land on us all the time in the form of meteorites, so in that respect this old material is not super-rare. It’s pretty rare -- I mean you don’t see that many meteorites lying around. But the fact that this is from a comet and known to be from a specific comet makes it an extremely rare and unique specimen.

And I’d also point out that while most of this material is presumably four and a half billion years old -- so it’s as old as the forming solar system -- we have good evidence for a component of meteorites and also in the comet dust that some of the material is older than the solar system. In other words, there are components present in the comet that existed as material before the solar system formed -- so they were in the dense cloud of gas, dust and ice from which our solar system formed before the solar system was a gleam you know, in anybody’s eye.

And then as part of that cloud started to collapse into the solar nebula and the planets and the sun started to form, some of that material from that previous phase survived into the comet without any alteration at all. So there are materials in the comet that are not as old as the solar system – they’re older than the solar system.

Jesse Carpenter: So does that older material present any unique surprises?

Scott Sandford: Well, I mean, we’re always very interested in that because that allows us to see beyond the origin of the solar system. It’s like if you watch a movie -- you only know what happens to the beginning of the movie. Well, in this case if you find these materials you can see what happened before the movie, you know? And so in the case of the organics we can see isotopic anomalies in hydrogen and nitrogen so these are ratios of the isotopes of these elements that are different from what we see in the solar system.

They can actually give us clues on what kinds of processes were happening in this original cloud, so they can tell us something about the environment and the chemistry and the physics going on in this cloud before the solar system even started. And in some cases we can find in the minerals isotopic anomalies that go even further back in time than that, and they tell us something about what was going on in a star that’s exploding. Okay some, when a supernova blows up and throws stuff out some of that material can form grains and those will have weird isotopic ratios.

And we find grains in meteorites that have these weird isotopic ratios, and so they tell you that this is a grain that’s older than the solar system and potentially even older than the cloud from which the solar system came from. And so if that isn’t cool, I don’t know what is. I don’t know how to describe it any more than that! So obviously a lot of us get very excited about that kind of thing. It’s a slightly different part of the science -- instead of learning about the formation of the solar system you’re learning about processes even beyond that.

But even then, they tell you something about the origin of the solar system because they tell you that when the solar system formed the conditions had to be such that those grains could survive.

(Music out/End Segment 2)
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