Sean Solomon, a member of the National Academy of Sciences, was awarded the Arthur L. Day Prize and Lectureship from the National Academies in 1999. He was also awarded the G. K. Gilbert Award from the Geological Society of America that year. He was president of the American Geophysical Union from 1996 to 1998, and he received that organization's Harry H. Hess Medal in 2005. He is a recipient of Caltech's 2006 Distinguished Alumni Award.

Mercury, the closest planet to the Sun, is a world of extremes. Its diurnal temperature varies from -180°C (-290°F) at night to 450°C (840°F) during the day. The compact spacecraft (1.62 x 1.62 x 1.32 meters) and its seven-instrument suite are thus specially outfitted for these exceptional conditions. As an additional precaution, the craft will pass over the hottest areas of the planet for only short periods.

(Image courtesy Johns Hopkins University Applied Physics Laboratory.)

Sean Solomon balances his position as director of the Department of Terrestrial Magnetism (DTM) with research in planetary geology and geophysics, seismology, marine geophysics, and geodynamics. His experience ranges from oceanographic expeditions on Earth to spacecraft missions to Venus, Mars, and Mercury.

As Principal Investigator for the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, Solomon heads a multiinstitutional consortium of scientists and engineers who operate the small, efficient MESSENGER spacecraft, which launched in 2004 and will reach its target orbit in 2011.

To date, the only craft sent to Mercury was Mariner 10 in the 1970s, and it imaged less than half of the planet. With a suite of seven miniaturized instruments, MESSENGER will address questions that are key to understanding terrestrial planet evolution. Solomon’s particular interests are to learn more about Mercury’s bulk composition and what that tells us about planet formation in general; to investigate its volcanic, tectonic, and internal evolution; and to understand how the planet’s magnetic field originated and determine whether there is a liquid outer core. Mariner 10 discovered that Mercury has a weak magnetic field, which may arise from an electromagnetic dynamo created in a liquid metallic outer core. Because the planet is small, scientists had thought that the core had cooled and solidified long ago. MESSENGER will investigate this question as well as the nature of the planet’s thin atmosphere and the composition of the permanently shadowed polar deposits.

Solomon is also Principal Investigator for Carnegie’s research as part of the NASA Astrobiology Institute (NAI). Astrobiology is an interdisciplinary approach to understanding the origin of life on Earth and its potential for existing elsewhere. Scientists from DTM and the Geophysical Laboratory are addressing the pathways of carbon and other ingredients for biology from elements and compounds in the interstellar medium to circumstellar disks and planetary habitats, to prebiotic chemistry under a variety of conditions, to early organic processes on Earth, to the search for biomarkers on Earth and other planetary bodies.

Solomon is also a team member on a variety of other projects including the Mars Orbiter Laser Altimeter (MOLA) investigation and the Plume-Lithosphere Undersea Mantle Experiment (PLUME). Data from MOLA, an instrument on the Mars Global Surveyor spacecraft, have been used to construct precise topographical maps to understand Martian geology, geophysics, and atmospheric circulation. PLUME is a combined land and ocean-bottom seismic experiment to image the mantle beneath the Hawaiian hotspot. Solomon is leading the land section of this project.

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