Lunar meteorites offer a more representative sampling of the Moon than the rocks returned by the Apollo missions, but scientists still do not know exactly where on the Moon they originate, according to researchers studying the rare space rocks. The meteorites, pieces of the lunar surface blasted into space and eventually falling to Earth, provide a window onto the Moon's earliest formation and could help answer outstanding questions about the lunar crust.
Only 835 lunar meteorites have been verified, making up 0.7 per cent of all meteorites that fall to Earth. The six Apollo missions collected some 382 kg of lunar samples, while three Soviet Luna missions returned 300 grams and China's Chang'e 5 and 6 missions 3.7 kg. Yet meteorites provide a more representative sampling of the Moon because they come from almost randomly distributed locations, according to Randy Korotev, research professor emeritus at Washington University in St. Louis.
'At the time of Apollo, we did not know that five of the six landing sites were in or near a geochemically anomalous part of the Moon,' Korotev told Universe Today. That region, called the Procellarum KREEP Terrane, is rich in potassium, rare earth elements and phosphorus. 'Apollo was a political not a scientific program,' he said.
Katherine Joy, professor of lunar and planetary science at the University of Manchester, said the meteorites are key to testing the lunar magma ocean hypothesis, which proposes that the Moon was once covered by a global ocean of magma. 'We can use the chemistry and age of these types of lunar meteorites to test the lunar magma ocean hypothesis,' she said.
The biggest puzzle is the unknown origin of each stone. 'Not knowing exactly where the rock came from is like missing the center pieces of a puzzle,' Joy said. Identifying a sample from a unique region such as Aristarchus or containing mantle pieces would reveal much about the Moon's interior and thermal history, she added.
Analysis
Why This Matters
- Lunar meteorites offer a more random and representative sampling of the Moon than the Apollo and Chang'e 5 missions, which all visited a geochemically anomalous region.
- Understanding the Moon's formation, including the lunar magma ocean hypothesis, depends on samples from diverse locations, especially the far side.
- The unknown origin of each meteorite limits how much scientists can learn, highlighting the value of future sample-return missions from unexplored areas.
Background
Lunar meteorites are pieces of the Moon's surface that have been ejected by impacts and later fall to Earth. Only 835 have been verified, representing 0.7% of all meteorite falls. They are found mostly in deserts and Antarctica. In contrast, the Apollo missions returned 382 kg of samples, but all from a region known as the Procellarum KREEP Terrane, an area rich in potassium, rare earth elements and phosphorus. The Chang'e 5 mission also sampled this region. Lunar meteorites are thought to come from randomly distributed locations, including the far side, making them scientifically valuable despite the lack of known provenance.
Key Perspectives
Randy Korotev (Washington University in St. Louis): argues that the view of the Moon would be very different if lunar meteorites had been studied first, as Apollo visited a geochemically anomalous part of the Moon and was a political program, not a scientific one.
Katherine Joy (University of Manchester): says lunar meteorites are key to understanding whether the near side and far side crust formed the same way, and that not knowing where each meteorite came from is like missing the center pieces of a puzzle.
What to Watch
- Future sample-return missions to geochemically unique areas such as Aristarchus or to the lunar mantle, which could provide critical insights into the Moon's thermal history.
- Advances in techniques to determine the exact source crater of lunar meteorites, which would greatly enhance their scientific value.
- The continued collection of lunar meteorites from deserts and Antarctica, potentially yielding more far-side samples.
Checked
12 claims in this story checked against 1 source: 10 supported.
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- SupportedLunar meteorites provide a more representative sampling of the Moon than Apollo samples, researchers say.Universe Today: “Yet lunar meteorites provide a more representative sampling of the Moon than Apollo, Randy Korotev, Research Professor Emeritus in the Dept. of Earth, Environmental, and Planetary Science at Washington University in St. Louis, told me via email.”
- Partly supportedMeteorites from random lunar locations fill gaps in understanding the Moon’s formation, but their exact origins remain unknown.Universe Today: “That's because they are thought to originate from literally all over the lunar surface, including the far side. Even so, only 835 lunar meteorites have been verified as such”
- Partly supportedLunar meteorites are pieces of the lunar surface blasted into space and eventually falling to Earth.Universe Today: “Lunar meteorites --- literally pieces of the Moon’s surface that have been displaced into Earth or solar orbit and have burned their way through our thick atmosphere --- arrive on our planet’s surface”
- SupportedOnly 835 lunar meteorites have been verified.Universe Today: “Even so, only 835 lunar meteorites have been verified as such, representing 0.7% of all meteorites that fall to Earth.”
- SupportedLunar meteorites make up 0.7 per cent of all meteorites that fall to Earth.Universe Today: “Even so, only 835 lunar meteorites have been verified as such, representing 0.7% of all meteorites that fall to Earth.”
- SupportedThe six Apollo landings collected some 382 kg of lunar samples.Universe Today: “The six Apollo landings collected some 382 kg of lunar samples, the authors note.”
- SupportedLunar meteorites provide a more representative sampling because they come from almost randomly distributed locations, according to Korotev.Universe Today: “Lunar meteorites in contrast come from almost randomly distributed locations on the Moon’s surface, says Korotev.”
- SupportedKorotev said: “At the time of Apollo, we did not know that five of the six landing sites were in or near a geochemically anomalous part of the Moon.”Universe Today: “At the time of Apollo, we did not know that five of the six landing sites were in or near a geochemically anomalous part of the Moon, Korotev told me.”
- SupportedThe anomalous region is called the Procellarum KREEP Terrane and is rich in potassium, rare earth elements and phosphorus.Universe Today: “We now know that all of the Apollo and China’s Chang’e 5 missions visited a geochemically atypical region of the lunar near side --- nicknamed the Procellarum KREEP Terrane, the Elements paper authors write. It’s an acronym for potassium, rare earth elements, and phosphorous”
- SupportedKorotev said: “Apollo was a political not a scientific program.”Universe Today: “Apollo was a political not a scientific program, says Korotev.”
- SupportedJoy said lunar meteorites can be used to test the lunar magma ocean hypothesis, which proposes a global magma ocean once covered the Moon.Universe Today: “We can use the chemistry and age of these types of lunar meteorites to test the lunar magma ocean (LMO) hypothesis, she says. The LMO is a hypothetical global ocean of magma that is theorized to have covered the moon up to several hundred km deep very early in the Moon’s history.”
- SupportedJoy said: “Not knowing exactly where the rock came from is like missing the center pieces of a puzzle.”Universe Today: “Each stone tells this amazing picture of the Moon's past, but not knowing exactly where the rock came from is like missing the center pieces of a puzzle, says Joy.”
