February 2017 Letter from the Director

Besides the record warmth we are enjoying in Washington this “winter”, something else unusual for DTM occurred in February - we hired a new staff scientist! We are very pleased to welcome Dr. Hélène Le Mével to the DTM geophysics group. Hélène is a volcanic geodesist, studying the sometimes miniscule ground motions around volcanoes to understand what is going on beneath them. She is a recent graduate of the University of Wisconsin-Madison where she used a variety of geodetic methods including interferometric synthetic aperture radar, high precision GPS, and gravity meters, to investigate the movement of magma and the establishment of new hydrothermal circulation beneath the Chilean volcano Laguna del Maule. This volcano is one of the large caldera-forming systems in the Andes, and as such, is known for the potential for very large, and very damaging, eruptions. Her work spans from the field studies needed for the measurement of ground deformation around active volcanoes, to the analysis of satellite radar data, to the geodynamic modeling of how magma movement in the shallow crust can produce the deformation measured at the surface. Hélène expands our efforts in volcano geophysics that started with the seismic imaging of regions of active volcanism by David James, carried on now by Lara Wagner, the installation of strainmeters near volcanoes by Alan Linde and Selwyn Sacks, and the active seismology studies of restless volcanoes done by Diana Roman. I am also pleased to report that Diana was selected as one of this years Carnegie Capital Science lecturers, so you all are invited to attend the presentation of her exciting work on May 31 at the Carnegie Headquarters in downtown Washington. The modeling done by Hélène intertwines well with that done by Peter van Keken and Peter Driscoll, all of whom are making good use of the still developing high-performance computing facilities now available within the Carnegie Institution. We welcome Hélène to the BBR campus and look forward to her contributions that will improve our understanding of how volcanoes work, with implications both for the basic science of magma movement in Earth’s interior, and the potential to better predict the hazards that would result from impending eruptions.

Helene Le MevelHélène Le Mével at her field area in Chile. Photo courtesy of Hélène Le Mével.

One thing that wasn’t unusual this month is that DTM scientists produced a range of interesting discoveries. Paul Butler and colleagues released a compilation of over 60,000 Doppler velocity measurements of over 1,600 stars made with the HIRES instrument on the 10-meter Keck telescope in Hawaii. In their own analysis of the data, preliminary indications of at least 100 exoplanets have been found. The data are open, and available through links on the DTM web page, for use by the astronomical community in the hunt for exoplanets, the evidence for which can be teased out of the small periodic velocity variations of the stars as they wobble about the center of mass of the planetary systems that orbit around them. The discovery of more exoplanetary systems continues to show the creativity of nature and its ability to form planetary systems with a wide range of planet sizes and orbital radii. The seven near Earth-mass planets recently reported around the small star TRAPPIST-1 provides a good example of a planetary system very different from our own.




On a related subject, but at a scale some 22 orders of magnitude smaller, Larry Nittler and colleagues, using new measurements of the proton-capture rate of 17O, were able to document that many of the micron or smaller presolar grains found in primitive meteorites derive from intermediate mass stars. Although such stars have long been expected to have contributed a large fraction of material to the interstellar medium, oxygen isotope analyses of presolar grains extracted from meteorites failed to show the expected isotopic signature of this source. The new proton-capture rates show that previous expectations of the isotopic composition of oxygen synthesized within intermediate mass stars are incorrect. The new data indicate that grains ejected from this common class of star do indeed form an important component of the presolar grains found in meteorites.

Yingwei PeterYingwei Fei (left) with Peter Driscoll (right) at BBR. Photo courtesy of Carnegie Science.

Some other good news for the department this month is that Peter Driscoll and Yingwei Fei were awarded a Carnegie Science Venture grant to investigate the physical properties of the materials that make up the interior of super-Earth sized exoplanets. The Carnegie Venture grants sponsor collaborative work between members of different departments with the goal of promoting cross-disciplinary studies. The Venture grants foster future work within the department, but we also have had success this month in preserving our history. BBR librarian, Shaun Hardy, was awarded a $10,000 grant from the American Institute of Physics’ Center for History of Physics to organize and preserve the archives of former DTM staff scientist Oliver Gish. Gish was a pioneer in atmospheric and terrestrial electricity in the early 20th century. His extensive files were donated to DTM in 2015 by his granddaughters Nancy Crow and Dorothy Crow-Willard. The papers provide a good look not only at Gish’s major contribution to the subject, but also to the organization of both American and international geophysics during its growth as an independent field of science in the first half of the previous century.

Among the postdocs arriving in the Fall, we are proud to report that two of them will be coming to DTM after being awarded, prestigious national fellowships. Our first Origins Fellow, shared between DTM and the Carnegie Observatories, Johanna Teske, will be continuing her work at Carnegie as a Hubble Fellow. Meredith MacGregor, a soon to be a Ph.D. astronomer from Harvard, was awarded an NSF Postdoctoral Fellowship and has chosen to take the fellowship at DTM. We welcome Johanna back and look forward to Meredith joining DTM in the Fall. 

Richard Carlson, Director, DTM
Carnegie Institution for Science
February 2017 Newsletter

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