Postdoc Spotlight: Cosmochemist My Riebe

My Riebe

When My Riebe was a kid, she used to run around the fields and forests of southern Sweden wondering how the hills she ran up and down formed, or what the stars she gazed at are made of. As she grew older, her questions became more daunting. What is the meaning of life? Where do we come from? What is her role in an endless universe? While many people might ask these questions of themselves at some point in their life, most do not take up the profession of actually trying to figure out the answers. Riebe did. Today, she is a postdoctoral associate at DTM working to understand how organic matter that did not form by biological processes in meteorites developed. These organic molecules delivered to the early Earth via meteorites and comets might have helped "kick-start" life, an answer Riebe has been searching for ever since she was a young girl. 

We talked to Riebe about what research projects she's currently working on and the research she hopes to do in the future in our latest Postdoc Spotlight.

DTM postdoctoral associate My Riebe in front of the Cameca NanoSIMS 50L at DTM. Photo courtesy of My Riebe, DTM.

DTM: When did you first become interested in your field of research? Why? 

My Riebe: As a kid, I spent a lot of time outdoors running around the fields and the forests in southern Sweden asking myself questions like: Why is this hill here? What are those stars made of? Why do these trees lose their leaves in the winter when the needles get to stay? Later, during my adolescence, I was asking myself the same big questions as all teenagers do: What is the meaning of life? Where do we come from? What is my role in an endless universe? Sometimes, I feel like I never left that stage. The difference is now I’m going to work every morning fighting to put together small pieces to the huge puzzle that is the formation of our Solar System, the origin of our home. It is really quite amazing that billions of years of nucleosynthesis in stars and evolution on Earth resulted in the rich life that exists today. I feel very privileged to get to study these processes.

DTM: How did you first hear about DTM? What brought you here?

Riebe: I became familiar with DTM during my Ph.D. at ETH Zurich in Switzerland. The institution has a very good reputation internationally and I was glad when I got the opportunity to come here and work with Larry Nittler and Conel Alexander, two of the top researchers in the field of cosmochemistry. There is also a great access to state-of-the-art instrumentation here at DTM. For me, one of the coolest machines here is the NanoSIMS, which allows us to make isotopic maps with a spatial resolution down to ~100 nm. With the NanoSIMS we can, for example, see that organic matter in meteorites is isotopically very heterogeneous, this gives us constraints on how the organic matter formed. 

A ~10 µm large fragment of insoluble organic matter from the meteorite Tagish Lake. The fragment is being transferred to a sample holder for analysis with the NanoSIMS using a micromanipulator. Image by My Riebe, DTM.

DTM: What excites you about your work? 

Riebe: I am very fortunate to work in such an interesting field! Sometimes, you get lost in the details and annoyed with something that doesn’t work. But if you look up and remember the big picture, what we do is really quite cool. I also really like working with people. I have the great pleasure of working with some really smart and inspiring people here at DTM and the Geophysical Laboratory, like Larry Nittler, Conel Alexander, George Cody, and Andrew Steele.

DTM: What research projects are you working on now at DTM?

Riebe: Currently, I’m working on organic matter in meteorites. This is organic matter that did not form by biological processes, but we are still working on trying to figure out exactly how it formed. It has been suggested that organic molecules that were delivered to the early Earth by meteorites and comets might have helped to “kick-start” life. Together with Conel Alexander, Larry Nittler, Jianhua Wang, Rhonda Stroud (NRL), Scott Sanford (NASA Ames), and Michel Nuevo (NASA Ames), I am looking to answer questions such as: How was the organic matter that we find in meteorites today formed? Was organic matter formed in the early Solar System or prior to Solar System formation? 

In particular, I am investigating the role of irradiation in the formation of organic matter. One characteristic of extraterrestrial organic matter is that it has much higher D/H and 15N/14N ratios than the Sun. In addition, large variations in isotopic compositions of hydrogen and nitrogen occur both between the bulk organic matter of different types of meteorites and on a µm and sub- µm scale in the organic matter of the same sample. The process(es) that formed organic matter likely contributed to these heavy isotopic compositions. One way that relatively complex organic molecules could have formed is through irradiation of ices of simple molecules. The irradiation breaks the bond in the molecules which, upon heating, recombine to form more complex molecules. Organic dust formed in this way could potentially be subjected to additional irradiation, producing heavier hydrogen. By comparing the isotopic composition of hydrogen and nitrogen in organic residues from ices subjected to controlled radiation exposures with those of organic matter in primitive Solar System materials, we are investigating how irradiation could have contributed to the formation of organics.

A hydrogen isotopic map made with the NanoSIMS of an interplanetary dust particle collected in the stratosphere by NASA. The bright spot has considerably heavier hydrogen isotopic composition than the rest of the particle. Image by My Riebe, DTM.

In another project, I am working together with Conel Alexander, Larry Nittler, George Cody, Andrew Steele, Dionysis Foustoukos, and Bjorn Mysen to better understand the effects of heating on organic matter in small particles during atmospheric entry. The organic matter in these samples has received a lot of attention as it sometimes has characteristics indicative of a very primitive nature, such as high D/H and 15N/14N ratios. However, this is not the case for all dust particles, perhaps because they have been modified by atmospheric entry heating. Our results show that flash heating simulating atmospheric entry heating clearly modifies IOM by driving off hydrogen to a higher degree than carbon and producing isotopically lighter hydrogen and nitrogen. These results indicate that the thermally unstable part of IOM is isotopically heavier in H and N than the thermally stable part and that atmospheric entry heating can make IOM in small particles less isotopically anomalous. Using Raman spectroscopy and Fourier Transform Infrared Spectroscopy we are currently investigating how to non-destructively identify the least heated particles. 

DTM: What research do you hope to pursue at your next job?

Riebe: So far, both at DTM and earlier during my Ph.D., I have mainly focused my research on the volatile elements in the Solar System. Investigating the origin, transport, and alteration processes of the volatile elements improve our understanding of the formation of the Solar System, including the Earth. I would like to continue working in this field at my next job. Part of the excitement of working in research is that you get to constantly develop new skills and attack new problems. Perhaps more than hoping to get to pursue research in a particular field, I hope that I get to keep challenging myself and learn new things. 

Making the most of a beautiful spring day at the BBR campus by bringing the laptop outside. Photo courtesy of My Riebe, DTM.

DTM: Where do you see yourself in 20 years? 

Riebe: In 20 years, I hope that I am mentoring the next generation of scientists as we are conducting cutting-edge science in a lab with equipment that we can only dream of today. Better spatial resolution, better sensitivity, better mass resolution, better yields, better ways to get rid of interferences, better everything! I think our understanding of the different bodies in the Solar System will be much improved over the next couple of decades by sample return missions. In 20 years, we should have samples from various asteroids and one of Mars’ moons. Hopefully, we will also have samples returned from Mars by then. Maybe we will have samples from Mercury? Enceladus? Titan? Where it’s from, I can’t wait to study them. 

DTM: If you could meet one science icon, dead or alive, who would it be and why?

Riebe: Marie Curie, she was such an amazing scientist. The pioneering work in radioactivity by Curie was the basis for a deeper understanding of the building blocks of atoms and the later discovery of isotopes. My work today is focused on isotopes, some of which are radiogenic. I wonder what it was like to do science in a time of so many fundamental, great discoveries. I also wonder how it was to be a female scientist more than 100 years ago.

My Riebe

Interview by Robin Dienel // May 23, 2017

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