On Monday (Dec. 5), a NASA spacecraft saw every landing site on the moon that humans have ever visited in person.
NASA's Orion spacecraft zoomed in close to the moon on Monday on the eighth anniversary of another Orion capsule's first brief test flight in Earth orbit in 2014. This time, the human-rated spacecraft was completing an engine burn near the moon to send the Artemis 1 mission back home as it entered the final week of a nearly month-long journey.
On a live NASA Television broadcast just before the successful engine burn, NASA spokesperson Sandra Jones spoke with deputy Apollo curator Juliane Gross about the six Apollo lunar landing sites visible behind the uncrewed Orion and how NASA's new moon program will build on Apollo's geological legacy.
Starting with the crewed Artemis 3 landing mission in 2025 or so, NASA plans to recover a wider range of rocks than basalts, which represented most of what Apollo astronauts found at their equatorial landing sites, Gross explained.
"We don't really expect a lot of basalts there," Gross said, referring to the south polar region of the moon where Artemis program astronauts will touch down. "That's more like a highland region," she added.
During the broadcast, Orion was flying roughly 2,000 miles (3,200 kilometers) above the sites where a dozen Apollo astronauts journeyed on the lunar surface during short excursions between 1969 and 1972. All told, six missions touched down: Apollos 11, 12, 14, 15, 16 and 17; Apollo 13 aborted its landing following a spacecraft emergency.
"Apollo wasn't so much about science," Gross said. "It was more about, 'We're actually going to the moon, and we can do it [with] the technology to show that we can do it." However, all lunar astronauts received at least some fundamental geology training — and that expanded later in the Apollo program.
Among the earlier missions' achievements was the pinpoint landing of Apollo 12, which proved that future excursions could do geology "in more difficult terrain," Gross said, referring to the highland equatorial regions targeted by the latter three Apollo missions. The astronauts and their geology teams tracked down younger basalts than found during Apollo 11, helping with relative dating of events on the moon, she said.
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Apollo 14 brought back about 92 pounds (42 kilograms) of lunar rocks, including some excavated by the collision that created the huge Imbrium basin, Gross said. The rocks, when exposed to so much heat and pressure, "reset" their geologic clocks — which is useful to date the impact event, she added. "We want to know when Imbrium formed, because it's such a big event that happened on the moon," she said.
Both Apollo 12 and Apollo 14 samples included a "weird component" called KREEP, Gross said. KREEP is an acronym geologists use for rocks that include potassium (K on the periodic table), rare earth elements (REE) and phosphorous (P).
Apollo 15 also collected KREEP, which scientist believe formed in the aftermath of a world-colliding moment when a Mars-size planetoid slammed into Earth, creating the moon. The rock type formed as the moon was solidifying from its "magma ocean" stage as the bits and pieces surrounding Earth began to coalesce, according to the Lunar and Planetary Institute.
Gross didn't detail the geology work of Apollos 15, 16 and 17 during the broadcast, but those astronauts did as much highland region science as feasible in three-day-long missions. These astronauts underwent extensive geology training led by California Institute of Technology geologist Lee Silver, who died earlier this year at age 96. NASA also flew a single professionally trained geologist, Harrison Schmitt, aboard Apollo 17; he found young "orange" soil during his surface excursions.
Gross called all the Apollo rocks "really, really cool" (the astronauts returned with some 842 pounds, or 382 kilograms, of material, according to NASA.) But all six excursions stuck to equatorial regions of the near side, which are not representative of all the moon has to offer.
"If I would give you six missions and you land them on Earth, and you land them all in Yellowstone National Park ... you get, geologically speaking, really interesting rocks," Gross said. "But they're not representative for the United States, or for the rest of the world."
The south pole landing site of Artemis, by contrast, will feature fewer basalts and more volatiles (lightweight elements like water) in the basin left by a huge impact that may have thrown up datable rocks telling us when the cosmic crash happened, Gross said.
Landing at the south pole could show "our own history and how the moon formed and evolved over time, better than we can with Apollo," she added. "We're missing a lot of rocks and processes with Apollo and hopefully, we can fill these gaps with Artemis."
Elizabeth Howell is the co-author of "Why Am I Taller?" (ECW Press, 2022; with Canadian astronaut Dave Williams), a book about space medicine. Follow her on Twitter @howellspace. Follow us on Twitter @Spacedotcom or Facebook.