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Marilyn fixing the mass spectrometer. The Pig Hat (Arkansas razor back) is put on to channel energy and intelligence. |
Most people work with
things they can see. Doctors deal with patients, real humans. Even if they are
trying to figure out a disease, they can look at blood and tissues, listen to
organ systems working away. Most ecologists deal with plants, animals, or soils
that they can hold or observe, count with their eyes, or manipulate. Even
chemists can carry out reactions with liquids, solids, and gases and create
products that can be seen, smelled, and weighed. Engineers create tangible
things—cars, computers, and bridges. Non-scientists sell things, nurse people
back to health, teach students, or manage money.
I’ve spent over 40 years
working with something that I can’t see, hear, smell, or taste—studying the
stable isotope, which can only be studied through a complicated series of
chemical and physical steps that result in a very small electric charge being
turned into a computer signal. The work is abstract. It’s picky. I have to be
satisfied with looking at a computer screen or a spreadsheet to get my work’s
reward.
Why in the world would
anyone spend four decades in such a pursuit? Because those small differences in
the types of isotopes—carbon, nitrogen, oxygen, hydrogen, and sulfur—can tell
those who have studied them how animals and plants have survived over billions
of years. We can understand chemical reactions that can’t be seen, but are
vital for living organisms to function. We can tell the types of foods you’ve
been eating. We can figure out where you were born and where you moved during
your childhood years.
My expertise did not
come suddenly, and it wasn’t learned from a book. When I was a graduate
student, I knew nothing. We had to memorize how a mass spectrometer—the
instrument we use for our measurements—worked, but had no real understanding.
As a postdoc, I made many mistakes in the laboratory. Broke a lot of glass
lines, blew up a few things. I learned from those mistakes, but truly, couldn’t
work my way out of any complicated situation. What I did learn during this time
was how to interpret the “magic numbers” that were calculated after all the
chemistry and physics was done right. I figured out something about the biology
of the organisms I was working on. The magic numbers were no longer
“magic”—they were real.
As a new staff member
building my own lab, I built up my experience by learning new things every year
or so. Many scientists spend their whole lives researching one slim topic. I
branched out quite early, which was key for developing a broad sense about
invisible isotopes and what they mean. Today, I can trouble shoot an instrument
from my desk in Mariposa, talking to students and postdocs via Skype. None of
us see the isotopes, but we measure times, temperatures, flow rates, and peak
sizes. They are learning the nuts and bolts of their chosen field.
We analyze substances
referred to as isotope standards. There are internationally recognized isotope
standards, commercial isotope standards, inter-laboratory isotope standards,
and individual laboratory isotope standards. These substances range from toilet
seats, peach leaves, plastic, oil, amino acids, milk protein, water, gases,
hair, feathers, fertilizers, extinct fossil shells to meteorites. Some believe
that if you are going to analyze animal tissue (e.g. squirrel monkeys), you
need to have a squirrel monkey standard. Every time we isotope geochemists
measure one sample, we analyze 3-4 standards of different types to compare it
to.
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Shuhei Ono's lab at MIT |
For a first pass, our
standards need to provide the correct “magic number” or else something is
wrong. One of the chemical steps might need adjustment. There might be a vacuum
leak. An electrical wire might be loose. If the numbers do come out matching
what others have measured, we then look to see if they are reproducible. The
laws of chemistry and physics are the same in Riverside, California, as they
are in Beijing, China. If we can make a measurement in August, we should be
able to repeat it in December. To make accurate and precise and reproducible
measurements of small, sub-microscopic particles demand that attention be paid
to the smallest details.
What sort of person
takes up this type of science? Starting in the 1960s, only a
handful—literally—was interested and involved in the field. When I started in
the 1970s, you personally knew almost everyone in the field. You read just
about every paper published with stable isotopes. Now, there are several
thousand scientists interpreting these “magic numbers” figuring out how the
Moon was formed, learning about processes on distant planets, and finding out
if Tour d’France bike racers used illicit performance enhancing drugs.
We’re a fairly tight
knit group in some ways. I correspond with about 100 different people a week on
the small details of stable isotope analyses. We criticize each other’s work,
usually supportively. Many of us meet once or twice yearly in person, where we
present our findings for critical review.
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My lab at UC Merced |
The hazards in this
field are numerous. We depend on explosive chemicals—fluorine gas, for example.
We generate poisonous gases—carbon monoxide, for example. We use deadly
chemicals—hot mercury and hot uranium. I’ve been burned, shocked, hit with
flying glass shards. Some of my colleagues have suffered much worse. With only
a very few exceptions, isotope scientists are careful people. We work well with
details.
Now, when I see a
landscape or learn about a new animal, I think, “How would stable isotopes help
figure how these things work?” It might be surprising to anyone else that
someone could spend such a long time devoted to things I can’t see, smell,
taste or hear. But, to others, not surprising at all.
We’re isotope nerds.
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Isotope Nerds at Univ. of New Mexico: Marilyn, Seth Newsome, Page Chamberlain (Stanford), Paul Koch (UCSC) | Back row: John Whiteman, Alexi Besser, Christy Mancuso, Emma Elliot-Smith |
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