NASA hopes modern tools and techniques will bring fresh discoveries from rocks that astronauts collected in 1972.
A day after their spidery lunar lander touched down on the moon in December 1972, Apollo 17 astronauts Gene Cernan and Harrison "Jack" Schmitt hammered a 16-inch-long aluminum cylinder into the lunar surface and extracted roughly a pound and a half of the rocky soil known as regolith.
The men — the last of the dozen NASA astronauts to walk on the moon — carefully sealed the so-called drive tube and brought it back to Johnson Space Center in Houston, where it has remained untouched for almost half a century.
Now, NASA says the time has finally come to crack the tube open. The space agency has selected nine teams to study the 47-year-old sample, as well as some moon rocks that were only briefly examined before being placed into long-term storage.
Most of the rocks and regolith collected during the Apollo program, which ended with Apollo 17, have already been examined. But NASA held these back so they could be analyzed by a new generation of scientists using tools and techniques that were unavailable in the 1970s.
"This is really an opportunity for the next generation to get their hands on some new samples," said Sarah Noble, a lunar scientist at NASA headquarters in Washington, D.C. "We always set aside plenty of samples for future generations. But at some point, you get to those future generations."
Another reason NASA has ordered up the new analysis of the old moon rocks is that the agency is gearing up for its Artemis program, which aims to send astronauts to the moon in 2024. Artemis astronauts — including the first female moon walker — will bring back more samples, and NASA wants to make sure scientists have the know-how to analyze a new batch of moon rocks.
Schmitt has likened NASA's decision to open the samples to a whole new Apollo mission. "You can always have another mission to the moon, just go back and work on the samples," he said in April at a Universities Space Research Association symposium on the past 50 years of space exploration in Washington. "I don't recommend that as your only mission to the moon," he joked.
The nine lucky teams picked to examine the samples come from NASA's Ames Research and Goddard Spaceflight centers, as well as the University of Arizona, the University of California, Berkeley, the University of New Mexico, Mount Holyoke College, the U.S. Naval Research Laboratory, the Planetary Science Institute and the Bay Area Environmental Research Institute.
Follow the water
Scientists hope their analyses will bring new discoveries about the moon, including the geologic history of the sites where the samples were collected, how rocks "weather" on the airless lunar surface, and how different storage techniques on Earth affect the samples over time.
Perhaps the most intriguing science question to be answered is how much water the samples contain. When scientists first examined Apollo moon rocks in the 1970s, they didn't find any water. But when scientists with more sophisticated equipment took another look in 2008, they found trace amounts.
Where the moon's water came from— and Earth's, for that matter — is a long-standing scientific mystery.
Scientists think a Mars-size object they call Theia struck Earth about 4.5 billion years ago, with debris from the impact clumping together in Earth's orbit to form the moon. If Earth already had water at that point, some of it may have been transferred to the newly forming moon. Another possibility is that both the moon and the Earth were pelted with water-bearing asteroids or comets at a later date.
The teams may be able to suss out the origin of water in the lunar samples by checking its so-called hydrogen isotopic ratio, which is essentially a unique atomic signature, said Jessica Barnes, a University of Arizona cosmochemist who is leading one of the research teams.
"Different objects in the solar system have different hydrogen isotopic ratios, so we can kind of use hydrogen isotopic ratios like a fingerprint to try to trace the water through time," she said.
One shot for science
The Apollo 17 drive tube is still vacuum-sealed at the Johnson Space Center; the other samples, from Apollo 15 and 17, were preserved in helium or placed into storage freezers.
Along with rocks and soil, the drive tube brought back by Cernan and Schmitt contains a smidgeon of noble gases that were locked within the rocks and soil. This too will be analyzed: NASA scientists will have one shot to open the tube and funnel the gas into a mass spectrometer, an instrument designed to detect the substances present in a sample. The abundance of noble gases in the sample can help determine its age.
The drive tube will be opened at the Johnson Space Center, while some of the new samples will be shipped to research teams in different locations, where various science instruments are available. The process and timing of the experiments are still being finalized, but work could begin as early as next year.
"We have an order from least destructive to most destructive analyses that we want to conduct," Barnes said. "You obviously don't want to ruin the part of the sample you want to look at before you've had a chance to do other analyses on it."
Fortunately for the scientists, they'll get more chances in 2024, thanks to the back-to-the-moon Artemis program. Preliminary plans call for an initial landing on the moon in 2024, followed by more surface visits each year through 2028 and the establishment of a permanent moon base.
NASA has yet to decide how many new moon rocks Artemis might bring back to Earth, but if the Apollo program is any guide, it could be a lot: In just six missions between 1969 and 1972, astronauts collected 842 pounds of samples for return to Earth.
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