The moon is not bone dry, scientists now know. But how many drops of water will thirsty astronauts find? No one knows for sure.
A robotic NASA spacecraft called Lunar Trailblazer, which launched Wednesday night from Kennedy Space Center in Florida, is aiming to provide a detailed map from orbit of the abundance, distribution and form of water across the moon.
Lunar Trailblazer tagged along for the ride to space on the same SpaceX Falcon 9 rocket as Athena, a commercial lunar lander built by Intuitive Machines of Houston, which will deploy a NASA instrument to drill in the moon and sniff for water vapors.
Athena will study one spot on the moon. Lunar Trailblazer will provide a global picture of water on the moon.
“That’s another exciting thing for us as we get more science into space with one launch,” Nicola Fox, the associate administrator for NASA’s science mission directorate, said during a news conference before the launch.
Less than an hour after liftoff, Lunar Trailblazer and Athena went their separate ways. Athena is taking a direct path to the moon, with landing scheduled for March 6, while Lunar Trailblazer set off on a meandering but fuel-efficient journey that will take four months to reach its destination. After it enters orbit, the spacecraft will make observations for at least two years.
One area of interest is water in the moon’s sunlit regions.
“Does it change as a function of time of day?” Bethany Ehlmann, a professor of planetary science at the California Institute of Technology who serves as the mission’s principal investigator, said in an interview. “You could think about it as almost like a frost coming and going.”
For decades, the moon has been regarded as a world devoid of water. But beginning in the mid-1990s, spacecraft found evidence of ice in the eternal shadows of craters in the moon’s polar regions.
In 2009, NASA slammed a rocket stage into one of the craters. The distinct color signatures of water were seen in the debris kicked up by the impact, confirming the earlier hints.
That same year, scientists made a surprising discovery that water was observed not just inside the polar craters, but also all around the moon. That came from observations of reflected light by a NASA instrument aboard Chandrayaan-1, India’s first lunar orbiter.
If water is somehow more widespread, that could ease future settlement of the moon, especially if significant amounts of water could be easily extracted from the soil. The water molecules could then be split to produce oxygen, for breathable air for astronauts. Hydrogen and oxygen can also be used to fuel rockets or generate power.
However, the instrument aboard the Indian spacecraft, designed to identify minerals on the surface, did not quite cover the swath of wavelengths needed to identify how the water was arranged.
The molecules could have been stacked as crystals of ice or stuck to the surface of minerals — what scientists call adsorbed. Those forms of water would probably not be very difficult to collect.
But the signal might also point to hydroxyl, a molecular group consisting of one hydrogen atom and one oxygen atom, as opposed to the two hydrogen atoms and one oxygen atom of water.
Hydroxyl would most likely be trapped inside rocks but could be released as water if heated to about 1,000 degrees Fahrenheit or more. That would require energy-guzzling ovens to bake piles of rock.
Lunar Trailblazer is carrying a scientific sensor, built by NASA’s Jet Propulsion Laboratory in California, that is similar to the one that was aboard Chandrayaan-1. But the new instrument is more advanced and covers all of the wavelengths needed to differentiate between ice, adsorbed water and hydroxyl.
The instrument can even make observations in the shadowed regions of the moon, which are not completely dark because sunlight often bounces indirectly into the crater. “That is the most fun part,” Dr. Ehlmann said. “It’s effectively a sort of double bounce of light.”
A second instrument, built by the University of Oxford in England, will measure the temperature of the surface. “The two instruments work together to get this simultaneous data set of water temperature and mineral composition all at the same time at the same place,” Dr. Ehlmann said.
Lunar Trailblazer is one in a series of lower-cost, higher-risk robotic science missions by NASA. The cost of building and operating the spacecraft is $94 million. But as a secondary payload on the Intuitive Machines mission, the cost of getting to space was only $8 million, much less than if NASA had purchased a rocket just to launch Lunar Trailblazer.
It is the third mission to launch from a program called Small, Innovative Missions for Planetary Exploration, or SIMPLEX. The first two failed once they got to space.
Two other SIMPLEX spacecraft lost their ride when problems with NASA’s Psyche spacecraft delayed the launch and changed the trajectory. One of those, Janus, which was to study asteroids, was canceled.
The other, ESCAPADE, which is to measure the magnetic fields of Mars, was then moved to the debut launch of New Glenn, the orbital rocket from Blue Origin, the space company founded by Jeff Bezos. But that mission was moved off when it appeared that New Glenn would not be ready in time to meet a tight launch window to send it on a specific path to Mars. It is still waiting for its launch.
Lunar Trailblazer also experienced travel changes. It was originally slated to ride along with the Interstellar Mapping and Acceleration Probe mission, or IMAP, but was then moved to the Intuitive Machines launch as the IMAP mission faced a delay.
“Lunar Trailblazer is being conducted in a fortunate time,” Dr. Ehlmann said, “because there’s a lot of interest in the moon, meaning there are opportunities to get a ride to the moon.”
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