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The following interview occurred on April 6, 2006 between Dr. Kevin McKeegan and Jacinta Behne, McREL Genesis education and public outreach team.
JB: Can you identify reasons why sample return missions offer benefits that other classes of missions can’t?
KM: I’m astonished that it’s a controversy. Genesis and Stardust represent the first returns in my career. The important thing about sample return is that the mission begins when samples return. It’s important to remind people that it took 10-15 years of studying moon rocks before the paradigm of how the moon formed by a giant impact — that study took about a dozen years to generate.
The most important reason is that it allows the normal operation of the scientific method in a reasonable timeframe. Samples are examined, hypotheses are put forward, and they are challenged. That’s the normal way we do science.
JB: NASA Administrator Mike Griffin has indicated a strong favor for involving higher education—specifically targeting graduate students—in future mission Education and Public Outreach (E/PO) work. How do you respond to that?
KM: That’s another good thing about sample return. It involves graduate students, post docs, and so on. Of course other students work on other missions, but the strength here is that they are grad students and remain on task for 4 years of sample return studies. There will be graduate student theses that come out of Genesis.
JB: If given the opportunity to propose a new mission based upon gathering new science and developing new technologies, what would that be? Are there gaps that you can identify that you know are critical?
KM: Sample return from the asteroid belt or from a comet — landing and getting a core of a comet. Everyone is very keen on return samples from Mars.
JB: What was it about this mission that said to you, “I need to be a part of this!”?
KM: For me it was straightforward — to measure the oxygen isotope of the sun. That was the overriding principal. The rest came along with it. I was involved in oxygen isotope measurements ever since my PhD. As a grad student I was at Washington University and Don Burnett, the Genesis principal investigator, was a frequent collaborator there.
JB: When you observed the hard landing on September 8, 2004, what was your second reaction?
KM: I was one of the master of ceremonies at JPL. My reaction was, “Maybe it’s not so bad. We have the sample.” It looked like it had buried itself. It was not a really bad thing. The really bad thing would have been if it didn’t come back, or we got nothing. It’s just a delay.
JB: Genesis hopes to verify that it has collected fossil pieces of the solar nebula. Is that realistic?
KM: For the major science objectives, yes, but it doesn’t mean that the list will be completed. Oxygen is the first one. If we get a good measurement of the oxygen, everyone will consider this to be an unequivocal success. In the case of oxygen, nobody knows. Just this week in Nature an article was published characterizing oxygen isotopes on the moon.
JB: At what point did you join the team?
KM: I was involved in Seuss-Urey (1993-4).
JB: Were you a part of the initial, pre-flight, collector identification team?
KM: Yes, we were heavily involved in characterizing the purity of the collector materials. I still think we got it right. That silicon carbide is good stuff.
JB: Tell me, why MegaSIMS [working at mega volts]?
KM: Fundamentally, we have an ion probe which was the best in the world instrument but couldn’t make the Genesis measurements. There were some things that were very straightforward to think about. Then there’s the problem that most of what we’d collect was still hydrogen. One of the problems that you get in ion probe analysis is that oxygen will attach itself to the atoms that you are interested in analyzing. So this causes a big problem for oxygen isotope elements — oxygen 16 is abundant, oxygen 17 is rare. If hydrogen attaches itself to 16 it's very close in mass to 17. So you have to measure the abundance of 17 in the presence of 16 hydride, which is much more abundant. So, the strategy that we use in MegaSIMS is to destroy or break apart this oxygen 16 molecule, more easily allowing us to analyze oxygen 17. (MegaSIMS destroys all molecules so that we can liberate the oxygen from the sample, but as we do that the hydrogen attaches itself to some oxygen, so we filter that so we can measure the samples.)
JB: When did you receive your first samples for analysis?
KM: Hopefully, Summer 2006.
JB: Is “identify, characterize, verify, and extract” your process?
KM: We’ll do all of that at once, in very small areas. We’ll get a sample, look at a 100 micron spot on the sample, dig a small hole — a very small hole, 0.1 millimeters on a side — and when we do that we’ll verify that it’s there.
MEGA means that we’re at mega volts, rather than kilo volts. The reason that we do that is that it allows us to efficiently destroy the molecules. Our job has to been to build this instrument. We start at the implantation stage and go to the final end in some number, to try to give us an idea of what it looks like. We go through the following steps:
- Get solar wind out
- Ionize and collect it
- Destroy the molecules
- Separate by mass (put each in a separate detector and count them). The efficiency is very high, with a 99% chance of counting it.
- Count relative abundances of the atomic ions (that’s what we’re after).
JB: In the end, what would you say will be Genesis’ greatest contribution to science?
KM: If the most abundant thing in the rocky planets is very different than what it started as, then there’s a very important mechanism in how planets are formed that we need to understand. There are no measurements of the oxygen isotopes in the sun that the theorists can claim correct. This would be a good contribution to science.
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