When we think of asteroids, we almost immediately think of giant rocks bouncing around like the iconic chase scene in Empire Strikes Back, and we often hear how they are remnants from the birth of the solar system. While the asteroids that comprise the Main Asteroid Belt of our solar system are not only spread far apart from each other, they are also not all made of rock. One asteroid approximately the size of the State of Massachusetts called 16 Psyche is made of metal, which planetary scientists hypothesize could be the remnants of a protoplanet’s core that didn’t build into a full-fledged planet. But how did such a unique asteroid form?
Now, an international team of scientists might be one step closer to answering that conundrum, as they attempted to ascertain how a large impact in the north polar region of 16 Psyche might have formed. The findings from this incredible study were recently published in the Journal of Geophysical Research: Planets and could help scientists gain insight into planetary formation and evolution, specifically during the early days of the solar system.
Using computer models, the researchers conducted 3-D simulations of impacts near the north polar regions of 16 Psyche and how these impacts could influence the interior characteristics of the large asteroid, specifically the distribution of metal within the asteroid. The team used 3-D models since the images from ground-based telescopes have provided limited data and NASA’s Psyche spacecraft, which launched in October 2023, isn’t slated to arrive at 16 Psyche until August 2029.
The researchers considered 16 Psyche’s physical shape into their models, noting that 16 Psyche is shaped like a potato while having a large impact basin near its north pole. Additionally, they also considered 16 Psyche’s interior structure, including whether it consists of one type of material throughout, or a homogenous model, and whether it’s layered with an iron core and volcanic rock on the outside. Finally, the team considered the asteroid’s interior porosity, or empty space, and how this played a role in impact crater formation, specifically what’s known as the crater’s depth-diameter ratio, or how deep the crater is compared to how wide it is.
In the end, the researchers developed several hypotheses regarding the interior of 16 Psyche, which they note they will confirm once the Psyche spacecraft arrives at the asteroid.
"One of our main findings was that the porosity – the amount of empty space inside the asteroid – plays a significant role in how these craters form," said Namya Baijal, who is a PhD Candidate at the University of Arizona’s Lunar and Planetary Laboratory and lead author of the study. "Porosity is often ignored because it's difficult to include in models, but our simulations show it can strongly affect the impact process and shape of craters left behind."
As noted, NASA’s Psyche spacecraft is slated to arrive at 16 Psyche in 2029, whose primary mission goals include determining if 16 Psyche is indeed a metal core remnant of a planetesimal, or an early planetary body. Through this, scientists hope to gain insight into how planets form, as this will be the first time in history that we can directly explore the interior on a planetary body. For context, while the distance from the Earth’s surface to its center is approximately 6,300 kilometers (4,000 miles), we’ve only drilled 12.26 kilometers (7.6 miles) into the Earth, or approximately 0.2 percent to the center of the Earth.
Part of accomplishing this primary goal will be to ascertain the interior composition of 16 Psyche, specifically regarding whether it’s layered or comprised of one mixture. The researchers in this study hypothesized that the 16 Psyche’s interior could play a role in crater morphology, specifically regarding its depth-diameter ratio. For example, they note that a stronger interior of the impact crater target sight would result in preserving large amounts of the impactor, whereas a weaker interior would result in preserving small amounts of the impactor.
Better understanding 16 Psyche and its origins will not only enable scientists to gain greater understanding of how planets throughout the solar system form and evolve, but also planets beyond the solar system. This could, in turn, help scientists understand both where and how to search for life beyond Earth.
What new insight will researchers make into asteroid 16 Psyche, including from the en route Psyche spacecraft? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!