Much of the moon’s frozen water is likely below the surface, out of view of orbiting spacecraft.
A drill on Athena will give scientists a first look at that water. The mission is named Polar Resources Ice Mining Experiment 1, or PRIME-1. The drill is named The Regolith and Ice Drill for Exploring New Terrain, or TRIDENT.
Near the south pole where temperatures are very cold, volatiles — chemical substances that easily change into a gas — are likely to be trapped in the soil.
The volatiles would give clues about the origin of the solar system, and they could also provide key resources for future astronauts, including water to drink, air to breathe and rocket fuel.
“It’s going to be important to understand, on the surface of the moon and beneath the surface, where these volatiles are, exactly what they are,” Joel Kearns, the deputy associate administrator for exploration in NASA’s science mission directorate, said during a news conference in February.
The drill was built by Honeybee Robotics of Altadena, Calif. It can drill to a depth of one meter.
When penetrating through loose soil, the drill bit turns like a normal drill. But the drill also has a mode that behaves more like a jackhammer “that we can turn on whenever we hit rocks or we hit ice,” Kris Zacny, vice president for exploration systems at Honeybee, said in an interview. “Frozen ground is as hard as pavement and even harder.”
The drill cuttings will be lifted out from the drill hole about four inches at a time and dumped on the lunar surface. The volatiles lurking in those cuttings, including water and carbon dioxide, will turn into gases and be detected by a mass spectrometer.
The drill also has two temperature sensors. One is the located right at the drill bit. The second, along with a heater, is eight inches above the drill bit. The heater also serves as a science experiment, allowing measurements of the flow of heat between the two sensors, which could reveal how much frozen water is in the lunar dirt.
If the soil is a good thermal conductor, heat from the heater would not change the temperature much. That is what would be expected if there is ice in the soil — what planetary scientists call regolith.
“But if the lunar regolith is a very good insulator and we turn the heater on, the temperature is going to go up very, very quickly because there is nowhere for heat to go,” Dr. Zacny said.
The thermal conductivity will be low if the regolith is dry.
The amount of power needed to push the drill downward will also reveal something about the material, whether it is loosely compacted soil or something hard like rock or ice.
