This summer, NASA will launch its first mission to a metallic asteroid, 16 Psyche, in the main asteroid belt between the orbits of Mars and Jupiter. Previous missions have explored rocky and icy asteroids, but Psyche’s composition is widely believed to consist of a considerable amount of metal. Of course, in today’s clickbait culture, googling Psyche will take you down the proverbial internet rabbit hole of stories about how it is worth more than the global economy. As enticing as that idea is, we are not going to scrap it and sell it for parts.
From a scientific perspective, though, Psyche is priceless.
In school, we learn that Earth has a layered structure: crust, mantle and core (inner and outer). Billions of years ago, as Earth and other planets were forming, solid bodies collided more frequent than today. Some of these collisions helped to build up these layers, creating larger bodies that became planets. Other collisions blew apart still-forming planets. The metallic asteroids are thought to be their remnants, cores of would-be planets that were stripped of their outer layers through high-velocity impacts.
The largest of these remnants, with an approximate diameter of 140 miles, Psyche may hold answers to questions about the early solar system, including how planets form or fail to fully form. The NASA mission will be equipped with instruments for measuring various properties of Psyche, and these data can provide more insight into the asteroid’s composition, including how much of it is metallic and how much empty space is present.
The mission will arrive at Psyche in 2026. In the meantime, computer modeling and simulations can help us to explore the feasibility of different material compositions of the asteroid. Psyche has two large impact craters in its southern hemisphere. Simulating their formation using Los Alamos National Laboratory’s supercomputers helps to visualize how such large and relatively shallow craters could have formed. Our simulations indicate Psyche may be a rubble-pile configuration, consisting of large boulders held together by gravity. Simulated impacts into rubble piles created crater shapes similar to those found on Psyche: wide but relatively shallow.
At Los Alamos, we are interested in solid bodies for another application: planetary defense. If a large body were on an Earth-crossing path, the more we knew about the object, the more likely an Earth mission could prevent a catastrophic impact through deflection. Perhaps the most commonly known event was the Chicxulub impact, which wiped out the dinosaurs about 65 million years ago, changing Earth’s environment forever.
Before panic sets in, note the frequency of such catastrophic impacts ranges from tens of thousands to hundreds of millions of years. To further clarify, Psyche is not on an Earth-crossing path and does not pose a threat. Data from the Psyche mission, however, can give us a better idea of how well our observational and modeling tools determine material properties of distant objects. Such information would be crucial to successfully deflecting future potentially hazardous objects.
An ongoing planetary defense mission may hold the answers to the question of whether we can deflect an asteroid with a kinetic impactor—essentially a big cannonball. NASA’s Double Asteroid Redirection Test (DART) mission, launched in November 2021, will travel to a two-asteroid system, where a smaller body, Dimorphos, orbits the larger Didymos. Like Psyche, Dimorphos is far away, limiting Earth-based observations of its material properties. Further, like Psyche, Dimorphos does not pose a threat to Earth.
The spacecraft will hit Dimorphos at more than 3.7 miles per second. The crash is expected to alter the orbit of the asteroid. Data will be collected before, during and after impact, and those data will be used to evaluate the success of the kinetic impactor method for planetary defense.
We are currently using the same modeling techniques we employed to understand Psyche to model impacts on Dimorphos. Dimorphos is considerably smaller than Psyche and can be modeled in more detail. We modeled Psyche using the nickel-iron alloy Monel, which likely has similar properties to metallic asteroids. Dimorphos, on the other hand, is rocky, so we use materials like basalt in our models. Because the DART mission has had years of planning, we can finely tune the Dimorphos models with more accuracy.
The good news is that these missions will give us additional data to update our models for more accurate results in the future. The data will also help us determine the uncertainties of our models and could highlight areas in which we could reduce those uncertainties.
When the Psyche mission launches this summer, and when the DART spacecraft crashes into Dimorphos this fall, be sure to raise a glass to science. 2022 is going to be the most exciting year for planetary science since I entered the field as a graduate student. For the first time ever, a mission will begin a trip to the main asteroid belt to visit a metallic asteroid, potentially opening a window to the early days of the solar system. Shortly after that mission launches, the DART spacecraft will reach Dimorphos on a one-way trip to an epic crash that could pave the way for a new era in planetary defense. Science is about trial and error, and although we do not always get it right, we never stop trying.