How and Why Is Mercury Different From Its Sibling Rocky Planets?

  • Speaker
  • Sean C. Solomon, Ph.D. Director, Lamont-Doherty Earth Observatory; Associate Director for Earth Systems Science, The Earth Institute; William B. Ransford Professor of Earth and Planetary Science, Columbia University
Date & Time


About Mathematics and Physical Sciences

Mathematics and Physical Sciences lectures are open to the public and are held at the Gerald D. Fischbach Auditorium at the Simons Foundation headquarters in New York City. Tea is served prior to each lecture.

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The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was the first to orbit the solar system’s innermost planet. Measurements acquired from orbit over four years, 2011-2015, provided the first global view of Mercury and changed our views on the formation and evolution of rocky planets.

In this lecture, Sean Solomon will summarize the scientific findings and the technical challenges from the MESSENGER mission. Mercury has a distinctive, chemically reduced composition marked by a high fraction of iron metal and abundances of volatile elements much higher than predicted by pre-mission planet formation theories. The planet hosts a dominantly dipolar internal magnetic field, but the dipole is substantially offset from the planet’s center. Mercury’s polar deposits, first detected with Earth-based radar, are confirmed to consist largely of water ice trapped in permanently shadowed regions inside polar impact craters. The water ice is mostly covered with a low-reflectance volatile material that is stable to temperatures somewhat higher than water ice and likely consists of organic material.

About the Speaker

Solomon is director of Lamont-Doherty Earth Observatory, the largest research division within the Earth Institute at Columbia University. He is also principal investigator of NASA’s MESSENGER mission to Mercury, the most comprehensive investigation yet of the planet closest to the sun. Solomon came to Lamont in 2012 after serving for nearly two decades as director of the Carnegie Institution’s Department of Terrestrial Magnetism in Washington, D.C. Among other roles, he served as principal investigator for Carnegie’s part of the NASA Astrobiology Institute, which seeks to understand the origin of life on Earth and its potential to exist elsewhere. He completed his Ph.D. in geophysics at the Massachusetts Institute of Technology in 1971, where he stayed on to teach and conduct research for two decades. He is a 1966 graduate of the California Institute of Technology.
Solomon  received the National Medal of Science in 2014 and is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. He has received numerous other awards, among them the Geological Society of America’s G. K. Gilbert Award and the American Geophysical Union’s Harry H. Hess Medal. When he stepped down as a director at Carnegie in 2011, his colleagues arranged to have a previously discovered asteroid named after him. Asteroid 25137 Seansolomon, about a mile and half wide, is currently orbiting the sun between Mars and Jupiter.
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