As astronauts prepare to explore the lunar surface again as part of the Artemis program, they may need to make use of the resources that already exist on the lunar surface, but first we need to understand what is there and how much.
Take water, for instance: Because it's a heavy, and therefore expensive, resource to launch from Earth, our future explorers might have to seek out ice to mine.
Once excavated, it can be melted and purified for drinking and used for rocket fuel. But how much water is there on the moon, and where might we find it?
This is where NASA's Lunar Flashlight comes in. About the size of a briefcase, the small satellite – also known as a CubeSat – aims to detect naturally occurring surface ice believed to be at the bottom of craters on the moon that have never seen sunlight.
Barbara Cohen, principal investigator of the mission at NASA's Goddard Space Flight Centre in Greenbelt, Maryland, said, “Although we have a pretty good idea there's ice inside the coldest and darkest craters on the moon, previous measurements have been a little bit ambiguous.”
Managed by NASA's Jet Propulsion Laboratory in southern California, the spacecraft is a technology demonstration: it will seek to achieve several technological firsts, including being the first mission to look for water ice using lasers.
It will also be the first planetary spacecraft to use a "green" propellant, a new kind of fuel that is safer to transport and store than the commonly used spacecraft propellant hydrazine.
“Scientifically, that's fine, but if we're planning on sending astronauts there to dig up the ice and drink it, we have to be sure it exists,” Cohen explained.
John Baker, Lunar Flashlight project manager at JPL, added, “A technology demonstration mission like Lunar Flashlight, which is lower cost and fills a specific gap in our knowledge, can help us better prepare for an extended NASA presence on the moon as well as test key technologies that may be used in future missions.”
Over the course of two months, Lunar Flashlight will swoop low over the moon's South Pole to shine its lasers into permanently shadowed regions and probe for surface ice. Found near the North and South Poles, these dark craters are thought to be "cold traps" that accumulate molecules of different ices, including water ice.
The molecules may have come from comet and asteroid material impacting the lunar surface and from solar wind interactions with the lunar soil.
Lunar Flashlight's four-laser reflectometer will use near-infrared wavelengths that are readily absorbed by water to identify any accumulations of ice on the surface. Should the lasers hit bare rock as they shine into the South Pole's permanently shadowed regions, their light will reflect back to the spacecraft, signaling a lack of ice.
However if the light is absorbed, it would mean these dark pockets do indeed contain ice.
The greater the absorption, the more widespread ice may be at the surface.
Cohen added, “The sun moves around the crater horizon but never actually shines into the crater. Because these craters are so cold, these molecules never receive enough energy to escape, so they become trapped and accumulate over billions of years.”
Cohen’s team includes scientists at the University of California – Los Angeles, John Hopkins Applied Physics Laboratory and the University of Colorado.
While the CubeSat can provide information only about the presence of ice on the surface, and not below it, Lunar Flashlight seeks to fill a critical gap in our understanding of how much water ice these regions possess.
"We will also be able to compare the Lunar Flashlight data with the great data that we already have from other moon-orbiting missions to see if there are correlations in signatures of water ice, thereby giving us a global view of surface ice distribution," added Cohen.
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