NASA's upcoming Artemis II mission is slated to return astronauts to the Moon no sooner than April 2026. Astronauts were last on the Moon in 1972 during the Apollo 17 mission .
Author
- César León Jr.
Ph.D. Student of Planetary Geology, Washington University in St. Louis
Artemis II will utilize NASA's Space Launch System , which is an extremely powerful rocket that will enable human space exploration beyond Earth's atmosphere. The crew of four will travel in an Orion spacecraft , which the agency launched around the Moon and successfully returned during the Artemis I mission .
But before Artemis II, NASA will send two missions to scout the surface of the lunar south pole for resources that could sustain human space travel and enable new scientific discoveries.
Planetary geologists like me are interested in data from Lunar Trailblazer, one of these two scouting missions. The data from this mission will help us understand how water forms and behaves on rocky planets and moons.
Starting with scientific exploration
PRIME-1 , or the Polar Resources Ice Mining Experiment, will be mounted on a lunar lander. It's scheduled for launch in January 2025.
Aboard the lander are two instruments: The Regolith and Ice Drill for Exploring New Terrain , TRIDENT, and the Mass Spectrometer for Observing Lunar Operations , MSOLO. TRIDENT will dig down up to 3 feet (1 meter) and extract samples of lunar soil, and MSOLO will evaluate the soil's chemical composition and water content.
Joining the lunar mining experiment is Lunar Trailblazer, a satellite launching on the same Falcon 9 rocket .
Think of this setup as a multimillion-dollar satellite Uber pool , or a rideshare where multiple missions share a rocket and minimize fuel usage while escaping Earth's gravitational pull.
Bethany Ehlmann, a planetary scientist , is the principal investigator of Lunar Trailblazer and is leading an operating team of scientists and students from Caltech's campus . Trailblazer is a NASA Small, Innovative Mission for PLanetary Exploration, or SIMPLEx .
These missions intend to provide practical operations experience at a lower cost. Each SIMPLEx mission is capped at a budget of US$55 million - Trailblazer is slightly over budget at $80 million. Even over budget, this mission will cost around a quarter of a typical robotic mission from NASA's Discovery Program . Discovery Program missions typically cost around $300 million, with a maximum budget of $500 million.
Building small but mighty satellites
Decades of research and development into small satellites , or SmallSats , opened the possibility for Trailblazer. SmallSats take highly specific measurements and complement data sourced from other instruments.
Multiple SmallSats working together in a constellation can take various measurements simultaneously for a high-resolution view of the Earth's or Moon's surface.
SIMPLEx missions can use these SmallSats. Because they're small and more affordable, they allow researchers to study questions that come with a higher technical risk . Lunar Trailblazer, for example, uses commercial off-the-shelf parts to keep the cost down.
These low-cost, high-risk experimental missions may help geologists further understand the origin of the solar system, as well as what it's made of and how it has changed over time. Lunar Trailblazer will focus specifically on mapping the Moon.
A brief timeline of water discoveries on the Moon
Scientists have long been fascinated by the surface of our closest celestial neighbor, the Moon. As early as the mid-17th century, astronomers mischaracterized ancient volcanic eruptions as lunar mare , derived from the Latin word for "seas."
Nearly two centuries later, astronomer William Pickering's calculations suggested that the Moon had no atmosphere. This led him to conclude the Moon could not have water on its surface, as that water would vaporize.
However, in the 1990s, NASA's Clementine mission detected water on the Moon. Clementine was the first mission to completely map the surface of the Moon, including the lunar poles. This data detected the presence of ice within permanently shadowed regions on the Moon in low resolution.
Scientists' first water detection prompted further exploration. NASA launched the Lunar Prospector in 1998 and the Lunar Reconnaissance Orbiter in 2009. The India Space Research Organization launched its Chandrayaan-1 mission with the Moon Mineralogy Mapper , M3, instrument in 2008. M3, although not designed to detected liquid water, unexpectedly did find it in sunlit areas on the Moon.
These missions collectively provided maps showing how hydrous minerals - minerals containing water molecules in their chemical makeup - and ice water are distributed on the lunar surface, particularly in the cold, dark, permanently shadowed regions.
Novel mission, novel science
But how does the temperature and physical state of water on the Moon change from variations in sunlight and crater shadows?
Lunar Trailblazer will host two instruments , the Lunar Thermal Mapper , LTM, and an evolution of the M3 instrument, the High-resolution Volatiles and Minerals Moon Mapper , HVM3.
The LTM instrument will map surface temperature, while the HVM3 will measure how lunar rocks absorb light. These measurements will allow it to detect and distinguish between water in liquid and ice forms.
In tandem, these instruments will provide thermal and chemical measurements of hydrous lunar rock. They'll measure water during various times of the lunar day , which is about 29.5 Earth days, to try to show how the chemical composition of water varies depending on the time of day and where it is on the Moon.
These results will tell researchers what phase - solid or liquid - the water is found in.
Scientific significance and what's next
There are three leading theories for where lunar water came from. It could be water that's been stored inside the Moon since its formation, in its mantle layer . Some geologic processes may have allowed it to slowly escape to the surface over time.
Or, the water may have arrived on asteroids and comets that collided with the lunar surface. It may even have been created by interactions with the solar wind , which is a stream of particles that comes from the Sun.
Lunar Trailblazer may shed light on these theories and help researchers make progress on several other big science questions, including how water behaves on rocky bodies like the Moon and whether future astronauts will be able to use it.
César León was previously affiliated with the California Institute of Technology in 2023 for a Summer Undergraduate Research Fellowship. He worked in Professor Bethany Ehlmann's lab (Principle Investigator of Lunar Trailblazer) on a different, non-Lunar Trailblazer project.
