Metallic Asteroids May Once Have Had Iron-Erupting Volcanoes

As a metallic asteroid such as Psyche cooled and solidified, iron volcanoes may have erupted on its surface. Elena Hartley/UC Santa Cruz

Billions of years ago when our Solar System was first forming, molten blobs of liquid metal once hung around suspended in space – the result of catastrophic collisions stripping protoplanets of their rocky outer layers in order to expose their iron-rich molten core.

Now, researchers at the University of California, Santa Cruz have reason to believe that as the metal cooled and solidified around the outside of these asteroids, volcanoes spewing liquid iron may have blown through a solid iron crust on their surface.

And there’s only one way to find out for certain.

The research is part of NASA’s Psyche mission set to launch in 2022 to a unique metal asteroid known as Psyche, which is orbiting around the Sun between Mars and Jupiter and seems to have the exposed nickel-iron core of an early planet – one of the building blocks of the Solar System. Scientists hope that an analysis of Psyche will help inform our understanding of how terrestrial planets once formed.

NASA's Psyche mission is set to explore one of the building blocks of planet formation: iron cores. JPL/NASA

"There are lots of these metallic meteorites, and now that we know what we're looking for, we might find evidence of volcanism in them," said researcher Francis Nimmo in a statement. "If material got erupted onto the surface, it would cool very fast, which would be reflected in the composition of the meteorite. And it might have holes in it left by escaping gas."

For example, deep in rocky terrestrial planets – including our own – scientists believe there are metallic cores far below rocky mantles and crusts. Since we can’t dig or see that far into our own earth, analyses of Psyche may help to explain how Earth might have formed.

"In some cases, [the object] would crystallize from the center out and wouldn't have volcanism, but some would crystallize from the top down, so you'd get a solid sheet of metal on the surface with liquid metal underneath," Nimmo said.

What exactly the iron volcanoes might have looked like depends on the composition of the asteroid's molten material.

"If it's mostly pure iron, then you would have eruptions of low-viscosity surface flows spreading out in thin sheets, so nothing like the thick, viscous lava flows you see on Hawaii," said graduate student Jacob Abrahams. "At the other extreme, if there are light elements mixed in and gases that expand rapidly, you could have explosive volcanism that might leave pits in the surface."

NASA's Psyche probe is expected to make it to the asteroid in 2026. Meanwhile, the team’s study has been accepted for publication in Geophysical Research Letters

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