Cosmochemist Larry Nittler studies extraterrestrial materials, including meteorites and interplanetary dust particles (IDPs), to understand the formation of the Solar System, the galaxy, and the universe and to identify the materials involved. He is particularly interested in developing new techniques to analyze different variants of the same atom—isotopes—in small samples. In related studies, he uses space-based X-ray and gamma-ray instrumentation to determine the composition of planetary surfaces. He was part of the 2000-2001 scientific team to hunt for meteorites in Antarctica.
Nittler is especially interested in presolar grains contained in meteorites and in what they can tell us about our cosmic origins. He develops and uses advanced microanalytical techniques to locate and analyze these tiny particles. The Solar System formed about 4.5 billion years ago from a cloud of gas and dust. Most of the original dust grains were vaporized during Solar System formation, but in the 1980s, researchers discovered that a fraction of these particles survived, trapped in meteorites. Presolar grains are about one thousandth of a millimeter in diameter. They predate other solid material in the Solar System and are believed to have formed in winds and explosions of ancient dying stars. The unusual abundance ratios of different isotopes in presolar grains compared with other Solar System products are their defining feature. They give researchers information about a number of processes, including how elements are synthesized inside stars, how the Milky Way galaxy evolves, and what the first Solar System materials were.
As Deputy Principal Investigator on NASA’s MESSENGER mission to Mercury, Nittler is playing a leading role in determining the chemical composition of the Solar System’s innermost planet. MESSENGER, led by former Terrestrial Magnetism director Sean Solomon, has been returning a wealth of scientific data since entering obit around Mercury in March 2011. By analyzing x-ray and gamma-ray signals emitted by rocks at the planet’s surface, Nittler and colleagues have determined that Mercury is surprisingly rich in magnesium, sulfur and sodium and low in iron. By comparing elemental maps to other data sets, Nittler is unraveling clues to the origin and geological history of Mercury, an end-member of planetary formation in our solar system.
Nittler recently worked on NASA’s Near Earth Asteroid Rendezvous (NEAR) mission to advance our understanding of the relationship of asteroids to meteorites. Although it is known from both calculations and observations that most meteorites originated from asteroids, it has been difficult to link specific asteroid classes to specific meteorite classes.
Nittler, with collaborators, reduced and interpreted data from NEAR to determine the elemental composition of the asteroid's surface. The data clearly showed that Eros is primitive; it has not differentiated into a core, mantle, and crust. Except for the ratio of sulfur to silicon, the elemental ratios agree with those measured in ordinary chondrites—the most common type of meteorite—indicating a possible relationship. The sulfur/silicon ratio, however, is much lower than in chondrites, a fact that most likely reflects some sort of “space-weathering” processes causing sulfur to volatilize and escape.
Nittler received his B.A. in physics from Cornell University and his Ph. D. in physics from Washington University. Before coming to Carnegie as a staff researcher in 2001, he was a postdoc at Carnegie, and a researcher at NASA’s Goddard Space Flight Center. He has also consulted with Lawrence Livermore National Laboratory for numerous years. For more information see http://www.dtm.ciw.edu/people/larry-r-nittler