Boston University Astronomers Detect Sodium Gas Ejected by Lunar Impact

9 October 2009

This press release on work done on a telescope located at McDonald Observatory was provided by Boston University.

FORT DAVIS, Texas — Boston University astronomers announced today observations of a cloud of sodium gas ejected from the Moon’s surface as a result of the NASA impact experiment that was part of its Lunar CRater Observation Sensing Satellite (LCROSS) mission. Jeffrey Baumgardner and Jody Wilson, senior research associates in the Center for Space Physics (CSP), conducted the observations from BU’s observing facility housed on the grounds of McDonald Observatory in Fort Davis, Texas.

“Sodium near the Moon’s south pole went from zero to blazing just after the impact!” Wilson reported to colleagues back in Boston.

Added Baumgardner: “We took a series of five-minute time exposures before, during and after the event and the detection is unambiguous.”

Sodium is a minor component of the lunar regolith (soil), but it can serve as a tracer of more abundant elements because it scatters (or reflects) sunlight very efficiently. The observing strategy of the BU team was to make their measurements at a point approximately 100 km above the lunar impact point, an altitude sufficient for sodium gas to be in sunlight (and therefore visible) and yet far enough away from the bright glare of the Moon’s surface.

“Sodium is continuously being ejected and lost from the Moon, creating an always present, but very faint and transient lunar atmosphere,” Wilson explained. “The ways that so-called surface-sputtering occurs on primitive bodies, such as the Moon, the planet Mercury and Jupiter’s moon Io, are topics of great interest to astronomers who study how atmospheres can escape from a large celestial body.”

Impacting meteors, the solar wind and sunlight are all agents that can eject sodium atoms from the Moon. While such surface-physics processes can be studied in laboratories here on Earth, this was the first successful attempt to conduct a “laboratory in space” experiment where the characteristics of the impactor were so well known.

“The full implications of these results will, of course, require detailed data analysis and modeling,” commented Michael Mendillo, professor of Astronomy at Boston University. “At this point, all we do know is that the BU team had a better night than the Red Sox.”

Baumgardner added: “The relation between what we saw in sodium and what the main objective of the experiment was --detecting possible signatures of water — will require coordinated analyses of all of the observations made on Earth and on board the NASA spacecraft.”

Research in BU’s Center for Space Physics involves interdisciplinary projects between members of the Astronomy Department in the College of Arts and Sciences and faculty, staff and students in the College of Engineering. Research areas include observational and theoretical studies in atmospheric, ionospheric and magnetospheric physics, planetary and cometary atmospheres, solar and heliospheric physics, and space weather.

Founded in 1839, Boston University is an internationally recognized institution of higher education and research. With more than 30,000 students, it is the fourth largest independent university in the United States. It contains 17 colleges and schools along with a number of multi-disciplinary centers and institutes which are central to the university’s research and teaching mission.

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Media Contact: Jeffrey Baumgardner, Boston University, 617-353-5639

Contacts at Boston University's Center for Space Physics:

Michael Mendillo, (617) 353-2629

John Clarke, (617) 353-0247

Supriya Chakrabarti, (617) 353-5990

Joshua Semeter, director, (617) 358-3498