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Title: Moon's Ancient Magnetic Field May Have Flickered On and Off

Link: https://science.slashdot.org/story/26/02/26/2...

sciencehabit quotes a report from Science Magazine: For decades, planetary
scientists have pored over a mystery hidden within the Moon rocks retrieved
by Apollo astronauts in the 1960s and '70s. Minerals in the rocks record the
imprint of a magnetic field, nearly as powerful as Earth's, that existed more
than 3.5 billion years ago and seemed to persist for millions of years. But
generating a magnetic field requires a dynamo -- a churning, molten core --
and most researchers believed the Moon's tiny core would have long since
cooled off, 1 billion years after it formed. Corroborating that picture are
other ancient Moon rocks of about the same age that suggest the field was
weak -- leaving planetary scientists baffled. Now, researchers are proposing
a new way to solve the puzzle. A paper published today in Nature Geoscience
theorizes that between 3.5 billion and 4 billion years ago, blobs of titanium-
rich magma melted episodically just above the core, rising in plumes that
drove volcanic eruptions on the surface. By intermittently stirring up the
Moon's core, these bouts of melting would have caused the Moon's magnetic
field to flicker on in short, powerful bursts. The paper "links a few
different concepts that people were thinking about separately, but hadn't
actually brought together," says Sonia Tikoo, a planetary geophysicist at
Stanford University who was not involved in the study.

Read more of this story at Slashdot.

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