LADEE reveals the force of meteoroid strikes on lunar exosphere
NASA researchers have announced new findings about the Moon’s exosphere, the thin layer of gas surrounding the Moon that’s one 25-trillionth of the density of Earth’s atmosphere. Data collected by NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft indicates the meteoroid strikes cause a predictable increase in the amount of two key elements within the lunar exosphere.
Space weathering – the physical process of meteor impacts, solar wind, UV radiation from the Sun, and collisions from cosmic rays – steadily transforms the surface of the Moon, releasing gasses into the lunar exosphere. An increase the emission of gasses was observed by the LADEE spacecraft as the Moon passed through a meteor stream, resulting in an increase in meteoroid impacts on its surface. The meteoroids can hit the lunar surface at velocities greater than 21 miles (34 kilometers) per second, converting their kinetic energy into intense heat and vaporizing part of the lunar regolith as well as the meteoroids themselves.
Within those observed gas emissions from the lunar surface are sodium and potassium ions. LADEE’s Ultraviolet and Visible light Spectrometer (UVS) instrument measured levels of sodium and potassium around the Moon every 12 hours for a period of more than 5 months.
These frequent readings revealed a rise in gas levels whenever meteor streams bombarded the Moon, with concentrations of both elements returning to normal levels after the stream had passed.
The two gases returned to normal levels at very different rates; whereas potassium returned to pre-shower levels within days, sodium took several months.
The findings were presented on Thursday at this week’s meeting of the American Geophysical Union (AGU) in San Francisco, California, and published in the journal Science. Scientists will apply these findings to exosphere models of the Moon and similar bodies to increase their understanding of how the Solar System originated and how it is changing over time.
“To understand the moon’s exosphere requires insight into the processes controlling it, including the interaction of meteoroid showers as well as solar wind bombardment and ultraviolet radiation of the surface,” said Anthony Colaprete, researcher at NASA’s Ames Research Center located at Moffett Field, California, and principal investigator of the UVS instrument. “Understanding how these processes modify the exosphere allows researchers to infer its original state. Since these processes are ubiquitous across the Solar System, knowledge gained by examining the Moon’s exosphere can be applied to a range of other bodies, granting us greater insight into their evolution through time.”
The Moon can serve as a nearby celestial laboratory for scientists studying the effects of space weathering on the lunar regolith and apply their observations to similar objects throughout the Solar System.
“These observations enable us to constrain the physical processes that contribute to the lunar exosphere,” said Menelaos Sarantos of NASA’s Goddard Spaceflight Center in Greenbelt, Maryland, and the University of Maryland, Baltimore County, and co-author of the paper. “We’re using these findings to build new exosphere models of how the space environment interacts with the surfaces of airless bodies, which we can use to better predict the processes and behaviors around similar bodies.”
LADEE was launched in September 2013 atop an Orbital ATK Minotaur V rocket from NASA’s Wallops Flight Facility in Virginia. The spacecraft orbited the Moon for approximately 6 months and collected detailed information about the lunar exosphere, the conditions near the surface, as well as the environmental influences on the lunar dust.
Video courtesy of NASA
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.