May 2019 Letter from the Director
Now in its 5th year, the all-campus annual poster session has become an ongoing tradition in May. With topics ranging from material science to exoplanets, and everything planetary in-between, discussion was plentiful on what was a beautiful Spring day. This year’s session was efficiently and effectively organized by DTM’s Rubin Fellow Jaehan Bae and GL’s Carnegie Postdoctoral Fellow Peng Ni. As in years past, participants included not only staff and postdocs from the two departments, but also colleagues from the University of Maryland and, for the first time this year, the Applied Physics Laboratory. The Applied Physics Lab began as an outgrowth of DTM’s defense-related research during World War II, but is now managed by John Hopkins University. The posters are now mounted along the wall of the tunnel connecting the Research and Abelson buildings, where they will remain until replaced by next year’s posters. If you visit BBR and are interested in getting a good impression of the breadth of cutting-edge science being done on our campus, be sure to stroll through the tunnel and take a good look at the posters. DTM alumni likely will find the poster prepared by Jan Dunlap of interest as it is a collage of the pictures of a very large fraction of the postdocs DTM has had the privilege of hosting over the past 30-35 years.
The poster session was held the day before the final Neighborhood Lecture of the season, presented by Sally Tracy, the most recent addition to the scientific staff of the Geophysical Laboratory. Dr. Tracy provided a very engaging tour through what high-pressure means, how one produces high-pressure conditions experimentally, and the science that can be done through the determination of material properties at conditions approaching those present in the center of giant planets. This type of work is a component of a new large-scale research effort within Carnegie that is focused on the role of a planet in establishing the conditions that make it habitable. The case for this effort was recently well made by GL Staff Scientists Anat Shahar and George Cody with DTM’s Alycia Weinberger and Peter Driscoll.
With the discovery of thousands of exoplanets, an important question is how many of these planets sustain environments that may have allowed life to develop. Judging from the exoplanetary systems discovered to this point, our own Solar System may not be a particularly good example of planetary systems in general with its out of the ordinary mixture of small rocky, volatile-poor, inner planets and distant gas giants. The extreme temperature of the surface of Venus compared to the clement surface of Earth shows clearly that planet size, and proximity to the host star, are not the only factors that determine conditions on planetary surfaces. But the question remains: What are the critical factors that would lead to an Earth-like planet elsewhere?An artist's impression of a sunset from a cold super-Earth discovered orbiting Barnard's star, the second closest star system and the nearest single star to Earth. Credit: Martin Kornmesser/ESO.
Carnegie’s Habitability Project has the broad goal of understanding what determines planetary habitability, but the answer to this question will require input from many different disciplines. Is the composition of the host star the primary factor in determining the composition of planets orbiting it? How much does the composition of a planet influence its interior dynamics, especially the question of whether a system of mass exchange between surface and interior similar to Earth’s plate tectonic system can operate? What role does the speed of planet formation play in allowing a planet to capture nebular gas or escape initial global melting driven by the heating of short-lived radioactive elements so it doesn’t end up as a water-poor “rock” like Earth? Is a distant gas-giant, like Jupiter, essential to the formation of Earth-like planets within the habitable zone? Do exoplanets have magnetic fields that can be detected, and are such fields essential to protect a planet from stellar winds capable of eroding its atmosphere and sterilizing its surface? The questions to be addressed in the Habitability Project thus include a range of topics that require the breadth of research expertise available within the Carnegie Institution. This type of topically-driven research is a historic strength of Carnegie Science that we hope to apply to obtain a better view of whether we are alone in the universe, or if not, where best to look for life elsewhere.
As a final note, I am pleased to report that representatives from the Smithsonian Institution are in the process of transferring a large fraction of our former colleague Erik Hauri’s extensive inventory of volcanic rock samples from around the world to the collections of the Smithsonian. Many of these samples were collected by Erik from remote sites in the South and West Pacific and the Aleutian Islands. Once incorporated into their collection and properly cataloged, the Smithsonian will make the samples available for loan to the scientific community for additional research and thereby extend the many contributions Erik made to understanding our home planet.