Metallic Asteroids Might Have Had Volcanoes Erupting Molten Iron. That’s So Metal

Remember the asteroid Psyche? It’s the largest known asteroid in the asteroid belt between Mars and Jupiter. It’s been in the news because of its unusual properties, and because NASA plans to launch a mission to Psyche in 2022.

Psyche, aka 16 Psyche, is unusual because it’s quite different from other asteroids. Psyche appears to be the remnant, exposed nickel-iron core of an early planet. Because of that, Psyche is a building block left over from the early Solar System, when planets were still forming. It’s like a planet without a crust.

But Psyche has another weird characteristic that scientists are keen to study: it’s much less dense than it should be, given the fact that it’s largely composed of iron and nickel.

A new theory tries to explain how this iron-nickel asteroid, with a metallic surface, could have a density far lower than it should.

Psyche is a class of asteroid called a pallasite, after Peter Pallas, a German who studied the Krasnoyarsk meteorite in 1722. That rock fell to Earth near the Russian city of Krasnoyarsk, and was the first pallasite ever found. Those were back in the days when nobody believed meteorites even came from space. It weighed about 700 kg (1500 lb) and is one of only 61 pallasites ever identified.

A slice of the Krasnoyarsk meteorite on display at the American Museum of Natural History. Image Credit: By Jon Taylor – Flickr: Krasnojarsk AMNH, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=16096581

While most asteroids consist mostly of rocky rubble, pallasites like Psyche are enigmatic, composed mostly of iron and nickel with olivine crystals entrained in it. Scientists think they formed when planetesimals collided, stripping away outer material and leaving the inner metallic cores. The asteroid then cooled from the outside in.

As it cooled, an alloy of residual melted pockets of iron, nickel and lighter elements like sulfur, might have erupted to the surface through fluid-filled cracks called dikes, creating virtual volcanoes of molten metal. That material would have created a coating on the topmost, rocky layer. That process is called ferrovolcanism.

Psyche may owe its lower-than-expected density to ferrovolcanism. Since Psyche, like other pallasites, is a mixture of core and mantle material, it may have experienced this type of mixing. The pockets of liquid metal mixed with sulfur are lower density than surrounding material, forming dikes that allowed ferrovolcanism to happen.

This diagram depicts a theoretical phenomenon called ferrovolcanism, where metallic asteroids erupt molten iron in a class of asteroids called pallasites. The ferrovolcanism might result when pockets of melted alloy rise to the surface. An upcoming NASA space mission to the asteroid Psyche may allow scientists to confirm their theory. (Purdue University image/James Keane)

“Our calculations suggest that ferrovolcanic eruptions may be possible for small, metal-rich bodies, especially for sulfur-rich melts and bodies with mantles thinner than about 35 kilometers or bodies where the mantle has been locally thinned by large impact craters,” said co-author of the paper, Brandon C. Johnson, associate professor of earth, atmospheric and planetary sciences at Purdue University.

Since Psyche is one of the most massive bodies in the asteroid belt, at about 200 km (120 mi) in diameter, ferrovolcanism may explain its low-density, while also explaining the surface metallicity it shows in radar and other evidence.

“Ferrovolcanism may have transported core material to the surface, causing the radar detections of metal,” Johnson said.

Psyche’s density is so low that it’s about half that of an iron meteorite. It’s also the largest metallic asteroid in the Solar System, that we know of. If its low density is due to ferrovolcanism, as the authors of the paper say it might be, it’ll be up to NASA’s mission to Psyche to figure it out.

NASA’s badge for the upcoming mission to the asteroid Psyche. Image Credit: NASA/JPL.

That mission is due to launch in 2022. It’ll be the first spacecraft to visit a metallic asteroid. Since ferrovolcanism is just a proposed model at this point, it’ll be up to that spacecraft to confirm its role. The mission to Psyche might also answer questions about the role metallic asteroids played in the development of the Solar System.

The paper outlining this work is published in the journal Nature Astronomy. It’s titled “Ferrovolcanism on metal worlds and the origin of pallasites.” The authors are Brandon C. Johnson, Michael M. Sori & Alexander J. Evans. 

More:

Evan Gough

Recent Posts

It’s Not Just Rocks, Scientists Want Samples Mars’s Atmosphere

Mars holds a very special place in our hearts. Chiefly because of all the other…

2 hours ago

Something’s Always Been Off About the Crab Nebula. Webb Has Revealed Why!

The Crab Nebula has always fascinated me, albeit amazed me that it doesn’t look anything…

7 hours ago

Lake Shorelines on Titan are Shaped by Methane Waves

Distant Titan is an oddball in the Solar System. Saturn's largest moon—and the second largest…

8 hours ago

Could We Put Data Centers In Space?

Artificial intelligence has taken the world by storm lately. It also requires loads of band-end…

11 hours ago

The JWST Peers into the Heart of Star Formation

The James Webb Space Telescope has unlocked another achievement. This time, the dynamic telescope has…

13 hours ago

Matched Twin Stars are Firing Their Jets Into Space Together

Since it began operating in 2022, the James Webb Space Telescope (JWST) has revealed some…

1 day ago