June 2019 Letter from the Director
They Are Not Just Rocks
As mentioned in last month’s newsletter, we have been working on the transfer of the extensive rock collection of our departed colleague Erik Hauri to the collections of the Smithsonian Institution. Most rocks, at least the kind we study, do not require storage under tightly controlled environmental conditions. The rocks in our collections tend to be heavy, usually of irregular shape with sharp edges, and often are sources of what most would consider “dirt.” As a result, they end up being stored in the spaces that no one else wants to use. With the rocks often wrapped in newspaper for cushioning during shipping, stored on shelves in decaying cardboard boxes, or more recently in 5-gallon plastic paint cans or 10-gallon milk cans from Mongolia, rock rooms often don’t visually convey the importance of the samples they contain. This is true at DTM, but also in most other Earth science research departments around the world. To the uninitiated, visits to “the rock room” tend not to elicit the same awe as do visits to the high-tech clean chemistry laboratories or advanced-instrumentation-rich labs that we use in our studies of the rocks. Nevertheless, the rock samples are the treasures that contain the record of Earth's history and the processes that have served to shape our planet to its current state.
Erik’s samples provide a good example of the importance of a group of rocks collected from around the world by a skilled scientist interested in deciphering the record of Earth history they contain. A large component of his collection is from a wide variety of small volcanic islands in the South Pacific that most have never heard of (Rapa, Rimatara, Tubuai, Upolu, etc.) and that can only be reached by local inter-island boat transport. Besides collecting the volcanic rocks that make up the islands, Erik returned with a number of mantle xenoliths that sample the material in Earth’s interior that melted to produce the ocean island volcanism. Xenoliths are fragments of the rock through which the magma flows to erupt at Earth’s surface. If the flow is sufficiently fast, pieces of the wall rock surrounding the magma conduit are broken off and carried to the surface, in some cases from depths of many hundreds of kilometers, as in the case of the diamonds studied by staff scientist Steve Shirey.Leslie Hale points to a xenolith from Erik Hauri's collection at DTM. Photo: Roberto Molar Candanosa, Carnegie DTM.
My own rock collection includes hundreds of pounds of these mantle samples from Mongolia and many areas of southern Africa. Another component of Erik’s collection is a series of samples from Hawaii and the islands of the Aleutians that were collected as close to the sites of eruption as possible. The quicker a lava is cooled, the more likely it is to retain a good fraction of the volatile compounds, such as water and carbon dioxide, present in the magma prior to eruption. Such material was key to Erik’s and colleagues’ goal of determining the flux of water and carbon transferred from Earth’s interior to its surface via volcanism. What makes these materials even more unique, and justifies their long-time archiving by the Smithsonian, is the data that we were able to obtain on the rocks during their study in DTM’s laboratories. The rocks in our collections have been used to:
- estimate the flux of water and carbon between Earth’s surface and interior
- understand the role that oceanic plate subduction plays in instigating the volcanism along convergent plate boundaries such as in South America, Japan, the Cascades, and the Aleutians
- track the return of surface materials into Earth’s deep interior and the rate that convection distributes and mixes away returned crustal materials in the mantle
- understand the timescale and processes by which Earth’s first crust was created
- determine the composition of Earth and how that relates to the meteoritic materials that sample the original building blocks of the planet.
The treasure trove of information contained within these samples has only partly been decoded by our work. As our understanding of Earth advances, and as analytical techniques expand and improve, new questions about Earth history can be investigated with these same samples. We are proud that the samples collected by Erik, and the work he did on them, has turned these “dirty” rocks into priceless scientific artifacts. Through the curation provided by the Smithsonian, the information the samples contain will continue to be read and deciphered well into the future.
Communing with Colleagues
Summer starts the time when our staff travel to the field and collect more rocks, to observe on telescopes around the world, especially those at Carnegie’s Las Campanas Observatory, and to meetings to exchange the latest discoveries with international colleagues. DTM’s leadership role in this latter activity is illustrated by staff scientist Larry Nittler serving as Chair for this year’s Gordon Research Conference on the Origins of Solar Systems. DTM staff scientist Alycia Weinberger will serve the same role in the 2021 conference on this subject. In June, DTM computer scientist Cian Wilson and postdocs Nathan Sime, Shi (Joyce) Sim, and Tim Jones, with the help of DTM staff Susana Mysen and Janice Dunlap, arranged and hosted the FEniCS19 workshop on campus. FEniCS is a continually developing open-source computing platform for solving partial differential equations that sees a good deal of use in the studies done here on the fluid dynamics of the slow movements of Earth’s interior. The workshop drew participants from the Universities of Cambridge, Luxembourg, Bergan, and Denmark, to name a few. Another event spearheaded by DTM staff was the Centennial Symposium of the Mineralogical Society of America (MSA), co-organized by staff scientist, and former MSA President, Steve Shirey that was held in the Elihu Root Auditorium at P-Street. Carnegie has been involved with MSA for nearly the whole history of its existence, with ten of MSA’s Presidents coming from Carnegie.FEniCS'19 attendees at Carnegie's Broad Branch Road Campus, June 13, 2019. Photo: Roberto Molar Candanosa, Carnegie DTM.
Two other extremely pleasing news items from June involve tributes to our departed colleague Vera Rubin. The first of these was a symposium hosted by Georgetown University, Vera’s alma mater, on the nature of dark matter in the universe, which was a subject Vera’s research brought into general acceptance within the astrophysics community. As a part of this event, Vera’s long-time friend and Princeton astrophysicist, Neta Bahcall, presented a marvelous public lecture on Vera, dark matter, and dark energy to a packed house in the Elihu Root Auditorium at P-Street.
The other news is that a bill has been introduced in Congress to rename the NSF and DOE funded Large Synoptic Survey Telescope, now under construction in Chile, as the Vera Rubin Survey Telescope. Both events speak to the major impact that Vera’s work had on our understanding of the universe, work that we are proud to note was done with Carnegie support during Vera’s 49-year career at DTM.