The asteroid 16 Psyche may be the remnant metallic core of a failed planet. We’re about to find out.
Inside our planet is a core that — as far as we can tell — is made of metal and spins to give our world its protective magnetic field. Without the help of Jules Verne, however, we can’t go look for ourselves.
But an asteroid called 16 Psyche might be the next best thing — the suspected remnant core of a planet, out there floating freely in space. We’ve only ever studied it from afar with telescopes, but soon, a NASA spacecraft of the same name will launch on a mission to study this fascinating object up close for the first time.
“We think Psyche may be the core of a body that had its outside stripped off,” says Ben Weiss at the Massachusetts Institute of Technology, Deputy Principal Investigator on Psyche. “So it’s potentially an opportunity to visit an exposed planetary metallic core.”
Psyche will launch on a SpaceX Falcon Heavy rocket from Cape Canaveral in Florida on October 12th. It will then take nearly six years to traverse some 4 billion kilometers to its target using an ion thruster, arriving in August 2029, where it will enter orbit around the potato-shaped object some 280 kilometers wide at its longest point. The Supercluster team will be on-site at Kennedy Space Center for liftoff.
The launch of the mission was moved off its original October 5th date due to an issue with the spacecraft. During routine pre-flight tests, engineers noticed that the settings used to operate the thrusters were incorrect. "The change allows the NASA team to complete verifications of the parameters used to control the Psyche spacecraft’s nitrogen cold gas thrusters," said a statement from NASA. "These thrusters are used to point the vehicle in support of science, power, thermal, and other demands, such as spacecraft orientation and momentum management."
Radar observations of Psyche, which orbits in the asteroid belt between Mars and Jupiter, show that it is extremely dense and more reflective than other asteroids. This means it might be rich in metal, with 40 to 60% of its bulk thought to be mostly iron compared to the fractions of metal seen in regular asteroids. What we don’t know is whether this metal will be mixed into the rock of the asteroid or appear as sheets or even lakes of metal on its surface.
“Right now it’s just wild speculation as to whether it’s gleaming, whether it’s a smooth surface or a rough surface,” says Weiss.
“We’ve speculated about glittering cliffs.”
The solar-powered Psyche spacecraft has two cameras and three instruments to study its namesake, allowing it to probe the asteroid’s composition, its surface, and even look for any evidence of a remnant magnetic field. “Maybe the body in its early state might have generated a magnetic field,” says Weiss.
The thinking is that Psyche might have begun life in the same way as Earth and the other planets, with a metallic rocky core forming and starting to pull in other material. At some point early in the 4.6 billion-year history of the solar system, however, when it was about twice its current size, Psyche was hit by a large impact. This may have torn away its still-forming outer layers and left only the metal core behind, or perhaps the object was destroyed entirely and re-formed as a metal-rich object mixed with rock.
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Support“It was starting to form as this little baby planet,” says Stephanie Jarmak, a research scientist at the Southwest Research Institute in Texas. “As it was forming, it got so big and hot in the center that it condensed this primary metallic core.” Psyche also rotates on its side relative to the Sun, perhaps supporting the impact idea, with several large craters thought to be on its surface from remote telescope observations. Another possibility, however, might be that Psyche simply formed in a metal-rich pocket of the solar system, rather than undergoing this impact-formation scenario.
In March, Jarmak used the James Webb Space Telescope (JWST) to study Psyche and plans to submit her results for publication in October. One of the goals was to see if there was any evidence of water mixed into the asteroid. “We’re trying to figure out if it’s this pristine sheet of metal, or if there are deposits of water-rich rocky material interspersed across its surface,” she says, which could tell us more about the object’s origin.
The high metallicity of Psyche has led to various overzealous headlines in recent years, some proclaiming Psyche to be worth “$10,000 quadrillion”. Such figures are speculative – we don’t really know exactly what Psyche is made of, while the prospect of mining asteroids for resources remains tentative at best. But that does not diminish the exciting interest in this object.
“Any of its components, in the far-flung future, would be useful for building components,” says Jarmak. “Even any of the [water-rich] material on Psyche’s surface could be equally valuable for fuel.”
The asteroid is part of a class of objects called M-type asteroids and, while it is fairly unique in this class, there are other similar objects in the solar system, such as the asteroid 216 Kleopatra. The planet Mercury also seems to look like the exposed core of a once larger planet. “It’s a weird planet because it’s basically a core with a little bit of rock on top,” says Weiss.
By comparison, Psyche seems to have its metallic core exposed on the surface. Studying it should hopefully teach us about planet formation, and not just in our solar system but around other stars too. “Psyche gives us an opportunity to start to understand how you could form something [like this],” says Weiss.
Much remains unknown about such objects. “We’ve sent spacecraft to rocky worlds like Mars, icy worlds like Europa, but this is an opportunity to go to a metal world,” says Weiss. “We want to know what it is like geologically. What does a volcano or impact crater look like on a metal world?”
At the end of this decade, we’ll find out. Get your asteroid mining picks at the ready.