Lunar Trailblazer

NASA’s Lunar Trailblazer ended its mission to the Moon on July 31, 2025. Despite extensive efforts, mission operators were unable to establish two-way communications after losing contact with the spacecraft the day following its Feb. 26, 2025, launch.

Selected by NASA’s Small Innovative Missions for Planetary Exploration (SIMPLEx) competition in 2019, Lunar Trailblazer aimed to map the distribution of the different forms of water that exist on the surface of the Moon. That would have helped scientists to better understand the lunar water cycle and inform future human missions as to where supplies of water may be found and extracted as a resource.

The mission was managed by NASA’s Jet Propulsion Laboratory and its science investigation was led by Caltech, which manages JPL for NASA.

While it is known that water exists on the lunar surface, little is known about its form, abundance, or distribution. The water may be locked inside rock and regolith – broken rock and dust – or it may collect as surface water ice inside the Moon’s permanently shadowed craters. In cold shadows, water molecules may also settle for short periods as frost: When the Sun moves across the sky during the lunar day, the shadows move, cycling these water molecules into the Moon’s exosphere and moving them to other cold places where they can settle once more as a frost.

Lunar Trailblazer would have used two cutting-edge instruments to help scientists better understand where these different forms of water are located, how the thermal properties of the lunar surface affect their distribution, and how the different forms of water change over time.

• The High-resolution Volatiles and Minerals Moon Mapper (HVM3) was a JPL-developed imaging spectrometer sensitive to the spectral fingerprints of the different forms of water and can make high-resolution maps.
• The Lunar Thermal Mapper (LTM) was developed by the University of Oxford in the U.K. and designed to detail the temperature properties of the Moon’s surface.