LIBS Operation on Airless Bodies
The excitation
characteristics of the LIBS plasma spark are pressure dependent, providing
the greatest signal in the range of 10-100 Torr. Optimization in
this pressure range occurs because of competition between free expansion
of the plasma, which limits the intensity of the signal at low pressures,
and plasma-shielding, which limits the laser energy incident on the surface
at higher pressures, affecting the amount of material that is ablated,
atomized, and excited to emit light. Although LIBS signals are reduced
at low pressures, the method remains useful for stand-off and in-situ analysis
of airless bodies…
We are carrying
out LIBS analyses of several different types of meteorites, indicative
of possible types of materials that could be encountered on asteroidal
surfaces…
Images of the surface of 433 Eros taken by the Near Earth Asteroid Rendezvous, or NEAR, mission. The picture on the left was taken at about 1,150 meters (3,773 feet) from the surface, and shows an area about 54 m (180 ft) wide. The middle picture was taken from a range of 700 meters (2,300 feet) and shows an area 33 meters (108 feet) across. The picture on the left was taken from a range of 250 meters (820 feet). It shows an area only 12 meters (39 feet) across. Courtesy of NASA/ Johns Hopkins University Applied Physics Lab