2011 Bowen Awardee

I was delighted and honored when Marc Hirschmann asked me to give the citation for his Bowen Award. I've known and admired Marc since we were graduate students together at the University of Washington, where he was advised by Mark Ghiorso. Soon afterward, he achieved a Promethean feat as a postdoc, "carrying the flame" of the MELTS solution model for natural silicate liquids from its originator, Ghiorso, to Ed Stolper's petrology group at Caltech. Given the very different cultures involved, building a bridge from Berkeley, Carmichael and Helgeson to Caltech, Harvard and Thompson, required a deep knowledge of the thermodynamic underpinnings of the model, plus an equal measure of tact, generosity and human understanding. Marc's successful feat initiated a very productive period of research all around him, particularly in collaborations with Ed and Ed's student, Paul Asimow. For example, Hirschmann and Stolper wrote a classic paper on melting of mafic veins in the mantle. They pointed out that, for small veins in a large, solid reservoir, thermal diffusion into the melting veins would offset the heat of fusion, leading to a super-adiabatic PT path, and to very large degrees of decompression melting. As with many such classics, the main result seemed immediately obvious once you read it, but it was completely unanticipated beforehand.

After moving to the University of Minnesota, Marc made a career change that initially worried me on his behalf. A theoretician until this point, he became an experimental petrologist, and set out to quantify the melting behavior of mafic rocks under mantle conditions. Given the diversity of natural mafic lithologies, and the resulting ten-dimensional complexity of the poorly explored P-T-X space into which he ventured, I was afraid that, in essence, Marc would go in there and never emerge. Clearly, I was wrong, and instead he and his students have been able to map this territory and delineate quantitative, general properties that apply to a wide range of compositions. The resulting data underpin much recent work by others on partial melting of two-lithology sources in the mantle source of ocean islands, large igneous provinces, and even mid-ocean ridge basalts.

Marc soon ventured into more uncharted terrain, first investigating the effect of water on mantle melting (alongside many other labs in a long tradition) and then - largely with his student Raj Dasgupta, who is emerging as an exceptional scientist in his own right - the less-studied effect of CO2. Again, tackling this topic using natural rock compositions posed the risk of getting lost in the wilderness, but this time I was less concerned. Instead, of course, Hirschmann and Dasgupta have forged valuable trails that will surely guide all those who follow.

Because of this experimental work, Marc has become a sought-after expert on volatile cycling in the Earth, writing a series of influential review papers on global geochemistry. If we stop and consider the breadth of these papers, and their fundamental implications for Earth history and planetary evolution, we can see that Marc has, de facto, been appointed by community consensus to a role that few attain, the small group of petrologists, geochemists and geophysicists whom we treat as authorities on the entire solid Earth system, and its interaction with the hydrosphere, the atmosphere and the biosphere. It's a select group, a really rare honor.

Given the range of Marc’s achievement and his high level of productivity, I am grateful for his input as a colleague. When time allows, I like to engage in scientific discussions via email that are more interactive and immediate than somewhat staid dialectic of peer-reviewed papers. Mark is a willing participant in such discussions, clearly as interested in understanding a topic as in the more tangible measures of scientific productivity.

As a result of all his success, achieved with grace and without rancor, Marc has been asked to fulfill a variety of leadership roles in the Earth Science community, for example serving as a long-time member of the MARGINS Steering Committee. While generally I am not very happy about being steered, I have been relieved to see Marc in these roles. I have always trusted him for unbiased, altruistic, well-informed and proactive leadership, in community service as well as in his research.

I am honored to know Marc, and I feel privileged to have played a role in celebrating his well-deserved Bowen Award.

I kind of took the long route to my career, so I don’t have time to mention everybody who inspired me. I’ll single out just a few. Were it not for Ian Carmichael, I wouldn’t have become a petrologist. I learned a ton about rocks and had great arguments with Charlie Bacon in two summers at Crater Lake. Mark Ghiorso taught me the interior secrets of quantitative petrology and Ed Stolper’s high expectations showed me a new level of rigor and how to ask bigger questions.

At Minnesota they solved our two-body problem even though there was supposed to be one job. Then we showed up with an infant and still they were more than welcoming to all 3. There, I’ve benefited from the great mentorship of David Kohlstedt and Larry Edwards and from a string of students, and research scientists who of course, do most of the work. Maik Pertermann, Jen Engstrom, Raj Dasgupta, Sandeep Mukherjee, Travis Tenner, Fred Davis, Ben Stanley, Hongluo Zhang, Patrick Hastings, Johnny Zhang, Dimitris Xirouchakis, Tetsu Kogiso, Ken Koga, Tony Withers, Cyril Aubaud, Paola Ardia, Haijin Xu, Anja Rosenthal, and at least that many undergraduates. I could tell stories about them all, so I’ll just say that if it weren’t for Tony Withers, my research enterprise would be a total failure.

I think of geology as the family adventure, and so I’m grateful that Donna and Naomi are with me on the ride. In the beginning Donna had to read all my manuscripts, listen to all my practice talks, and to hear about all my stress regarding, well, everything. It’s true I did the same for her, but her stress didn’t derive from quite the same level of pessimism.

When I was a student and I heard or read acceptance speeches of this kind, I must confess they always left me… demoralized. It seemed future awardees all had had wonderful times as students, had easily landed the most enviable jobs, and so on. Their careers seemed to have been effortless sequences of success. I found this hard to relate to. Now here I am, sounding like one of those guys I kind of resented back then. Of course, I now see that it’s natural to gloss over the tough parts. And yet, there were tough parts along the way. Talking about rejected papers and the like is boring, so I just want to share with you one of the challenging days I remember, when as post-doc, I accidentally threw out what was to that point my only successful partial melting experiment. I spent the entire next morning inside a dumpster, going through every disgusting bag of trash to find a polished capsule smaller than a pea. Standing in that dumpster, apart from telling myself, “I’m such an idiot”, I was also thinking, “What will I tell Ed if he walks by and sees me in here?” Anybody who has stuck around long enough has stories like these. I’m fortunate to have had more successes than dumpster days.

I’m humbled to receive an award given previously to so many illustrious people and I feel particularly lucky that I’ve had the benefit of friendship or mentorship from quite a few of them. I'm even more humbled when I think of some of my peers who have not received this recognition but are certainly more worthy than me. Thank you.