Isotope Geochemist, UCSD
The following interview occurred on June 14, 2006, between Dr. Mark Thiemens, and Jacinta Behne, McREL Genesis education and public outreach team.
JB: In your opinion,
what strengths do sample return missions bring to NASA's body
of solar system science?
MT: Precision. I fly rockets for a living myself. We fly and collect atmospheric whole air samples from the top of the atmosphere and bring the samples back. You can measure things in situ, but the real advantage of returning science is that you can gain much more from high precision and accurate measurements.
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 (EPO) work. How do you respond to that?
MT: I think it’s a great idea. I think he should do the next thing, which is putting money into it in a significant way. Programs in which I’m now working are getting cut 15-20% —not an optimal way to train graduate students. The level of funds available isn’t enough to support graduate students in a meaningful way. They make about $22,000 in salary, and with benefits, cost $45,000. Average funding, in many programs, is $60-70,000, which will cover a grad student, but leaves very little left to do the science.
I hope that graduate student involvement will be pursued.
I’ve had a number of students who have benefited from
funding, and they go out into the world with exceptional laboratory
training. Summer programs are great for the graduates. For
example, NASA programs at Johnson Space Center, Kennedy Space
Center, and Moffett Field have been extraordinarily important.
The quality of science that comes out of NASA funding is overall
extraordinary. Programs such as these highly leverage the
funding for basic science while training the future generation
of space scientists, which is vital.
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?
MT: My own personal preference is for return
atmospheric samples from Mars, and in a mission that does
not involve landing. So here's the pitch. We have Martian
meteorites and measured them. Pathfinder has been glorious
in the scientific return. We're now focusing on biomarkers
for origins of life on other planets such as Mars. Part of
what I do is measure samples of the oldest rocks on Earth
to learn about the evolution of life. There are two things
that arise from these studies. One, beginning life on earth
is going to highly likely to involve nitrogen fixation. The
by- products are well known, with nitrous oxide one of them.
This has the potential to provide a molecular marker
O2 is no good because you can chemically and abiogenically
make it other ways. What you are left with is nitrous oxide
for which you need biology. The internal molecular isotopic
distribution of it is somewhat like a DNA fingerprint. If
you can collect a sample of the atmosphere, you might be identifying
a biologic source. This is the potential marker but one that
requires a very high laboratory precision measurement, You
can't measure it in situ on Mars because of the exacting requirements.
You need to return it to Earth to make the relevant measurement.
The machine that we use to do the work weighs 2,000 pounds
and cannot be flown!.
JB: What was it about
this mission that said to you, "I need to be a part of
MT: Oh, it didn't really work that way in
my case exactly. Here's how I got involved. In the mid 1970s
I was at the University of Chicago doing my post doctorate
research. I was measuring solar wind looking at nitrogen isotopes,
and then came here as an assistant professor. One day at the
annual Lunar and Planetary Science Conference, Don Burnett
spoke to me over beer and pretzels. "Mark, you measure
solar wind for nitrogen in linear samples. Wouldn't it be
interesting to measure the current oxygen isotopic composition?
Would you want to work on it? What do you think?" At
this point, my engagement began, which was before the development
of the original proposal and is how I got involved.
JB: When you observed the hard landing on September 8, 2004, what was your second reaction?
MT: In my mind, I always assumed the worst
case, that it's going to crash. My whole protocol for
doing the analysis is that we can do "dirty stuff."
Realism is that stuff crashes on occasion, an experience from
my own rocket sampling program. The question is whether or
not, if it crashed, the silicon carbide would survive. There
were contingencies from the beginning by the Genesis team.
For my analysis, it's made so that you can do the measurement
even with disaster.
JB: Given the sample
return scenario, retrieval, curation, and ultimate dissemination,
what would you identify as the mission's greatest challenge
in approaching science analysis?
MT: The same that it's always been. It's
just that the samples are so small. With oxygen, the implications
are significant for understanding the evolution of the planets
in our solar system. Along with the small size, the issue
of needed high isotopic precision is formidable, though the
stakes are high. Oxygen has been the big mystery of cosmochemistry
since the beginning of time. It's unique on the whole periodic
table in terms of the ubiquity of the anomaly and its size,
as well as its abundance in planets.
JB: Genesis hopes to verify that returned samples hold the key to the building blocks of our original solar nebula. Is that realistic?
MT: In this game of oxygen isotope lottery,
in the 1970s, oxygen isotopes were identified as weird, according
to Bob Clayton in Chicago. There's no chemical way to do this.
There has to be a nuclear process. This was the main doctrine
for 15-20 years and is a very big deal. No other element on
the whole periodic table is anomalous in the way that oxygen
is. The whole solar system is involved in creating its peculiar
oxygen isotopic composition, and on such a massive amount
of material. It now appears certain that chemical processes
reproduces the oxygen isotopic composition. There are several
models that propose to account for the mechanism by which
the anomalies arise and key to proving which is correct, is
a high precision oxygen isotope ratio measurement of the sun!
My sense is that when we get this solar result, the sun is going to look a whole lot like the Earth. Forgetting about the scale of things, I hope to get measurements to eliminate some theories, and introduce new ones.
I will eventually have a piece of the concentrator target. I discovered something else while preparing for the final measurement of oxygen. In one of our other research efforts, we are collecting small atmospheric particles at the pier at the Scripps Institution of Oceanography. The goal is to use the oxygen and sulfur isotopic composition of these particles to detail how much emissions from Asia affect California. As a result, we developed the technique to measure small amounts of sulfur for its isotopes and we hope to make these measurements now on the Genesis samples, though this was not originally planned. Sulphur is significant cosmochemically and may add to our understanding of solar system processes. The requirement is that we have to measure really, really small amounts of sulphur. I this could be quite interesting and is a measurement that we can make simultaneously with oxygen and at no additional cost.
JB: Were you a part of the initial, pre-flight, collector identification team? If so, how did you determine which materials would fly as good sample collection hardware?
MT: Yes. The number one on the hit list is cleanliness. We were involved with measurements to help make the determination along with the team.
JB: You are investigating oxygen using fluorine gas to remove water and organics from the surface of the wafer, then burning off layers of silicon carbide with a laser to free the captured oxygen for analysis with mass spectrometry. Tell me why? What do you hope to learn?
MT: The easiest way to think of it is that
to burn off a surface is like laser shaving--we can burn off
a prescribed amount of surface and vaporizes everything for
analysis. The system is a large laser coupled
to a mass spectrometer. I’m going to etch the brown
stain off with fluorine before getting to the solar wind oxygen.
The final spot will be a centimeter on the side. It makes
a trench about 10 microns. Angstroms--think of hairs.
There is another aspect of local importance to the Genesis
mission. You know the first rendition of this proposal was
Seuss- Urey. I was hired here to replace Hans Seuss and took
over Urey's old laboratory, so there was an emotional component
JB: When did you receive your first samples for analysis?
MT: Within the last month--Spring 2006--yet
JB: Is "identify,
characterize, verify, and extract" your process? If so,
why? If not, how would your describe the analytic cycle that
you are using?
MT: Yes--pretty much true of all of us.
JB: Have you reached
a point where you can say that "we've had our first breakthrough?"
If so, can you share any information with us that will help
us understand the significance of this science?
MT: Well, the breakthrough is being able to make the measurement. This approach to coming up with a faster answer on other samples than originally planned is a nice advancement.
JB: If today you were to characterize the chemical picture of your Genesis work for me, what would it look like?
MT: It's pretty much based on understanding
oxygen as a global way to understand the solar system. The
one thing everyone agrees on is that you can't understand
how the solar system formed and evolved happened if you don't
understand the chemistry of oxygen.
JB: Tell me about the historical connection between Genesis and Harold Urey and Hans Seuss.
MT: They (Suess and Urey) wrote a classical paper on the Origin of the Elements paper in 1947. This is a very big deal in Cosmochemistry. I used to always explain to students in chemistry classes what a major breakthrough this paper was. It was in this paper that we learned that the abundance of the elements derives from their creation in stars.
JB: Do you help the public understand the small scale?
MT: It's really hard to give a concept of scale.
When you get down to nanometer levels, it's difficult to provide
any realistic scale because one is at the size of atoms.