Nov 16, 2021 - Science

A little space rock with strange origins

The Moon seen from the International Space Station.

The Moon seen from the International Space Station. Photo: NASA

A relatively small piece of rock that sticks close to Earth in its orbit around the Sun may actually be a broken-off hunk of the Moon, according to a new study.

Why it matters: Learning more about the possible origins of mysterious objects even in nearby space can help researchers piece together the evolution of our solar system from its earliest days to now.

State of play: A new study in the journal Nature Communications Earth and Environment suggests the object Kamo'oalewa has properties that indicate it could actually be a piece of the Moon that broke off and orbits the Sun while remaining near Earth.

  • Originally, scientists thought Kamo'oalewa, which was discovered in 2016, was an asteroid captured by Earth's gravity at some point in the past, but this new data suggests otherwise.
  • The team used a telescope to put together a spectrum — the reflected light — from the space rock's surface and matched it to Moon rocks, which look very similar.
  • "This spring, we got much needed follow-up observations and went, 'Wow, it is real,'" Ben Sharkey, an author of the study, said in a statement. "It's easier to explain with the Moon than other ideas."

The big question: How did Kamo'oalewa break off from the Moon and form?

  • Scientists don't yet have an answer to that question, but it's possible a meteor impact cleaved some material from the Moon, allowing it to form the Ferris wheel-sized object.
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