PROVIDENCE, R.I. [Brown University] — NASA has given the green light to build a small satellite that will investigate surprising evidence of water on the surface of the Moon. The spacecraft, called Trailblazer, could launch as early as 2023.

Carle Pieters, a professor emerita in Brown University’s Department of Earth, Environmental and Planetary Sciences, will serve as a co-investigator on the mission. Bethany Ehlmann, a professor at the California Institute of Technology who earned her Ph.D. at Brown in 2010, will lead the mission as principal investigator. Another Brown Ph.D. graduate, Rachel Klima, who is a senior scientist at the Johns Hopkins University Applied Physics Laboratory (APL), will assist Ehlmann as the mission’s deputy principal investigator.  

For many years, scientists had assumed that the Moon was bone dry. But that idea started to change in 2009, when an instrument called the Moon Mineralogy Mapper (M-cube, or M3) that flew aboard India’s Chandrayaan-1 spacecraft detected an extremely thin veneer of water molecules across much of the Moon’s surface. Trailblazer is designed to fill in critical details of what was found by M3, an instrument for which Pieters was the principal investigator.

“For me, Trailblazer is particularly exciting because the thrust of this mission follows directly from our 2009 discovery,” Pieters said. “We haven’t returned to the Moon to follow up on that surprising water discovery until now.”

Trailblazer’s water-sniffing instrument will be an updated version of M3 called the High-resolution Volatiles and Minerals Moon Mapper (HVM3). The mission team will use the instrument to take detailed looks at the surface at different times in the lunar day. One goal is to see if the water on the surface is embedded in lunar rock or if it’s mobile — decreasing and replenishing molecule by molecule in response to solar radiation.

If the water is indeed mobile, it would provide definitive evidence of an active water cycle on the Moon, and perhaps other airless bodies. Over time, such a cycle could provide a source for the ice deposits detected in permanently shadowed craters near the Moon’s poles. Trailblazer is designed to peer inside those permanent shadows to map ice deposits using only light scattered from the crater rim.  Understanding the source of those ice deposits has important implications for ongoing lunar exploration and the possibility of a long-term lunar research base.  

“We know this thin layer of hydration occurs across much of the Moon’s surface, so it is a fundamental property of Earth's nearest rocky neighbor,” Pieters said. “We now have the opportunity to study the mysterious lunar water cycle further.”

The mission was selected for development as part of NASA’s Small Innovative Missions for Planetary Exploration (SIMPLEx) program. With a length of only about 3.5 meters with its solar panels fully deployed, Trailblazer is small enough to ride along with other instruments in their way to the Moon.

“This is a truly exciting little mission that could give us big scientific return,” Pieters said. “I’m looking forward to working with the mission team to make discoveries that provide valuable insight into our Earth-Moon system.”

With approval from NASA to design and build the satellite, a launch could come as early as 2023 or 2024.

The mission will be managed by the Jet Propulsion Laboratory, which Caltech manages for NASA. In addition to Brown, Caltech and APL, other mission partners include Lockheed Martin, the University of Oxford, Pasadena City College, Northern Arizona University and the University of Central Florida.