GTCC’s Cline Observatory and the GTCC Foundation present
Our 19th annual Fall Astronomy Day Lecture
Friday, 2 October 2015, 7:30 p.m.
Koury Auditorium, GTCC, Jamestown
The MESSENGER Spacecraft Mission to Mercury: Surprises from the Innermost Planet
Sean Solomon, Lamont-Doherty Earth Observatory, Columbia University
With all the attention the New Horizons Mission to Pluto has generated about the outer solar system this summer, it is easy to overlook the fact that NASA just wrapped up a multi-year mission to explore the solar system’s innermost planet, Mercury. The MESSENGER Mission to Mercury was only the second spacecraft to visit the planet, and the first in over three decades! The Mariner 10 flybys of Mercury in 1974 allowed only a partial mapping of Mercury, and raised many interesting questions. MESSENGER finally brought us back to Mercury with a robust and long-term monitoring program, spending over four years in orbit and giving planetary scientists an unprecedented look at the innermost planet. Our speaker, Dr. Sean Solomon, of the Columbia University’s Lamont-Doherty Earth Observatory, was the lead investigator in charge of the MESSENGER Mission, and his lecture at GTCC will present what we have learned about the small world at the inner reaches of our solar system.
This event is free and open to anyone with an interest in astronomy. No reservations are necessary. Cline Observatory will be open for viewing after the talk, weather permitting.
This note is being sent to the TriStar distribution list – please note that this lecture is in a different location from TriStar. Koury is Building #19 on this campus map: http://www.gtcc.edu/media/10954/jamestowncampusmap.pdf
The MESSENGER Spacecraft Mission to Mercury: Surprises from the Innermost Planet
Sean C. Solomon
Lamont-Doherty Earth Observatory, Columbia University
Mercury, the smallest and innermost solar system planet and the planet formed from the densest materials, remained comparatively unexplored for more than three decades following three flybys by the Mariner 10 spacecraft in 1974–75. Space exploration of Mercury resumed with the selection for flight, under NASA’s Discovery Program, of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. Launched in 2004, MESSENGER flew by the innermost planet three times in 2008–2009, was inserted into orbit about Mercury in March 2011, and operated until propellant was exhausted in April 2015. MESSENGER’s chemical remote sensing measurements showed that Mercury has a low-iron surface composition that differs from those of the other inner planets. Moreover, surface materials are richer in volatile constituents – those that would be removed by high temperatures – than predicted by most planetary formation models. Global image mosaics and targeted high-resolution images reveal that Mercury experienced globally extensive volcanism, including large expanses of plains erupted as flood lavas and widespread examples of pyroclastic deposits emplaced during explosive eruptions of volatile-bearing magmas. Bright deposits within impact craters host fresh-appearing, rimless depressions or hollows, often with high-reflectance interiors and halos; such hollows likely formed through the geologically recent loss of one or more volatile compounds. On the basis of imaging, neutron spectrometry, near-infrared reflectance, and thermal models derived from measured topography, Mercury’s polar deposits first detected with Earth-based radar consist largely of water ice in permanently shadowed cold traps within polar impact craters. In most locations, the water ice is covered with a 10–30-cm-thick layer consisting of a low-reflectance volatile stable to temperatures somewhat higher than water ice and likely consisting of impact-derived organic material.