Lunar Prospector

Mission Profile

Lunar Prospector was NASA's third Discovery-class mission, launched on 7 January 1998 aboard an Athena II rocket to a low polar orbit around the Moon to map its surface composition and gravity field with a highly capable neutron spectrometer suite. The mission's most significant finding was strong evidence for water ice in permanently shadowed craters near both lunar poles, detecting hydrogen concentrations consistent with water ice deposits of 1 to 10 billion tonnes. Lunar Prospector also produced the first comprehensive magnetic field and gravity maps of the entire lunar surface, revealing mascons and confirming the Moon's small iron core. At mission's end in July 1999, the spacecraft was deliberately impacted into a suspected polar ice deposit in a final attempt to detect a water vapor plume, though none was conclusively detected.