Giant Craters May Reveal if Psyche is a Lost Planetary Core

A new peer-reviewed study models the large impact crater on asteroid 16 Psyche's north pole using 3D collision simulations, establishing specific predictions about the asteroid's interior that the NASA Psyche spacecraft will test when it arrives in 2029. The paper, published this month in the Journal of Geophysical Research: Planets (https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JE009231), does not tell us what Psyche is made of. That question remains open. What it does is build the framework that will eventually answer it.

The lead author is Namya Baijal, a PhD candidate at the University of Arizona's Lunar and Planetary Laboratory (LPL). Co-authors include Erik Asphaug, an LPL professor and specialist in planetary collisions, and Adeene Denton, a NASA Postdoctoral Program Fellow at Southwest Research Institute. The University of Arizona press release (https://news.arizona.edu/news/large-craters-offer-clues-origin-asteroid-16-psyche) has the full methodology and direct quotes from both researchers; the paper itself is paywalled.

The paper arrives as the Psyche mission approaches a critical milestone. In April 2025, the Psyche spacecraft lost thrust. A pressure drop in the primary xenon fuel line, traced to a valve malfunction, took all four Hall-effect thrusters offline. For two months, the spacecraft sat coasting on momentum while engineers at NASA's Jet Propulsion Laboratory (JPL) worked the problem. The fix was to switch to the backup xenon line. By June 16, 2025, full propulsion had resumed (https://science.nasa.gov/blogs/psyche/2025/06/20/nasas-psyche-spacecraft-resumes-full-time-propulsion/), according to a NASA Science Blog post. Mission planners scheduled three months of makeup thrusting through November 2025 to recover the lost trajectory margin. The Mars gravity assist flyby — the critical slingshot toward the asteroid belt — is now in May 2026, about two months out, and still on schedule. August 2029 arrival at the asteroid remains the target.

What the simulation is doing

Asteroid 16 Psyche — discovered in 1852, roughly 140 miles across, and the largest known metal-rich asteroid in the main belt — has a large concavity near its north pole. About 30 miles wide and 3 miles deep. The question is what formed it and what its shape reveals about the interior.

The team ran three-dimensional Smoothed Particle Hydrodynamics (SPH) simulations — a standard method for modeling large-scale collision dynamics — using a real 3D shape model of Psyche derived from ground-based telescope observations. They varied impactor size and assumed interior composition, and tested two competing structural models.

A layered model: an iron-nickel metallic core with a thin rocky (silicate) mantle, consistent with a differentiated protoplanet that lost its outer layers in a violent ancient collision. A homogeneous model: a uniform blend of metal and silicate throughout, consistent with a more catastrophically mixed formation history similar to certain metal-rich meteorites found on Earth.

The best match to the observed crater — a roughly 3-mile-wide impactor at a 45-degree angle, moving at about 3 miles per second — is consistent with both models. This is the important part: the paper does not determine which model is correct. Both produce craters that fit what's observed. The paper's purpose is to build the prediction framework that spacecraft data will test. As ScienceDaily noted in its coverage (https://www.sciencedaily.com/releases/2026/03/260317064440.htm), the crater dimensions and impact parameters are independently confirmed by this secondary source.

Porosity is the methodological contribution

What's technically significant beyond the Psyche-specific findings is the modeling approach. The team incorporated realistic porosity — the fraction of empty space inside the asteroid's interior — into their SPH simulations, something previous work on comparable problems largely skipped because it is computationally expensive to include. It matters: a porous asteroid absorbs impact energy more efficiently than a dense one, producing deeper, steeper craters with less ejecta scattered across the surface. Depending on the assumed porosity, the predicted crater morphology shifts enough to affect which interior model fits the eventual spacecraft data. Building it into the workflow now, before the mission has collected a single measurement, is the Arizona team's primary contribution.

Universe Today (https://www.universetoday.com/articles/giant-craters-may-reveal-if-psyche-is-a-lost-planetary-core), which covered the paper in its first week, noted the 2029 spacecraft arrival but did not report the 2025 propulsion incident or the approaching May 2026 Mars flyby.

Why Psyche matters

The asteroid has attracted disproportionate attention partly because of a number that circulates constantly: "$10 quintillion in metal resources." Economists and planetary scientists have noted that this figure is economically incoherent — there is no extraction technology for asteroid-scale material, and delivering that volume of iron-nickel to Earth's commodity markets would collapse them. The number persists anyway. It is not the reason this mission exists.

The actual reason is older and stranger. Earth has an iron-nickel core. So do Mars and Venus. We know roughly what they're made of from seismic measurements and planetary models, but we've never directly observed one. The deepest drill hole in human history — the Soviet Kola Superdeep Borehole — reached 12.26 km. That's about 0.2 percent of the way to Earth's center. "We can't get to the cores of Earth or Mars or Venus, but maybe we can get to the core of an early asteroid," Asphaug said in the UA press release.

Psyche may be that core, sitting in the asteroid belt, available for inspection. Or it may not be. Four competing origin hypotheses have been debated since the asteroid's discovery 174 years ago: intact differentiated core, partially differentiated body that retained some crust, primordially metal-rich remnant that never fully melted, or a body whose interior was mixed by repeated impacts. Three decades of radar and spectroscopic observation from Earth have not resolved it. The Baijal et al. paper is a more rigorous version of the prediction framework. The spacecraft is the experiment.

What's actually coming

According to the JPL mission page (https://www.jpl.nasa.gov/missions/psyche/), the science objectives are: determine whether Psyche is a core or an unmelted metal-rich body; characterize relative surface age and topography; assess whether the asteroid incorporates light elements expected in Earth's high-pressure core; and understand the role of impacts in shaping metal-rich bodies.

The spacecraft — built by Maxar Technologies, a satellite manufacturer, and managed by JPL — was originally led by principal investigator Lindy Elkins-Tanton at Arizona State University; she has since moved to the University of California, Berkeley. It carries four instruments: a multispectral imager, gamma ray and neutron spectrometers, a magnetometer, and a radio science system. According to JPL, the Psyche mission is the first interplanetary demonstration of Hall-effect electric propulsion — the same thruster type that failed in April 2025 — and the first deep-space test of laser optical communications beyond the Earth-Moon system.

The Mars gravity assist flyby is in May 2026. Orbital insertion at Psyche is planned for August 2029.

The propulsion glitch in 2025 was the mission's most serious incident to date. The backup xenon line worked. There is no tertiary option if it does not. The spacecraft has three more years of cruise ahead of it before the science begins.

The prediction framework the Arizona team published this month will be waiting when the spacecraft gets there — assuming it gets there.