Unlocking Psyche's Secrets: Simulations Predict Asteroid's Inner Composition
New research from the University of Arizona's Lunar and Planetary Laboratory has utilized simulations to model the formation of a large crater on asteroid 16 Psyche. These simulations aim to provide predictions regarding the asteroid's internal composition and origin, aiding the interpretation of data from NASA's Psyche mission, which is scheduled to arrive in 2029.
About Asteroid 16 Psyche
Located in the main asteroid belt between Mars and Jupiter, Asteroid 16 Psyche is the 10th-most massive asteroid in this belt. It is recognized as the largest known metallic asteroid, measuring approximately 140 miles in diameter. Fewer than 10% of main-belt asteroids are metal-rich, making its formation a significant subject of scientific investigation.
Hypotheses for Psyche's Origin
Several hypotheses currently exist regarding Psyche's formation:
- It may be a remnant building block of an early planet that was fragmented by collisions.
- It could be a fragment of a planetary body that once had separated layers but subsequently lost its rocky outer mantle.
- Alternatively, it might be an ancient remnant that was either initially rich in metal or developed a mixed composition of rock and metal following repeated impacts with other asteroids.
Research and Simulation Methodology
Researchers at the University of Arizona's Lunar and Planetary Laboratory conducted simulations focused on understanding how a large crater near Psyche's north pole may have formed. The findings of this study were published in JGR Planets.
Namya Baijal, a doctoral candidate at LPL and lead author, stated that large impact basins can offer insights into an asteroid's interior composition.
The simulations generated predictions for Psyche's overall composition, intended to be tested against observations from the upcoming spacecraft mission. The team utilized a 3D shape model of Psyche, derived from telescope observations, to simulate the formation of a concavity approximately 30 miles across and three miles deep. Simulated impacts occurred at speeds typical for the asteroid belt, around three miles per second.
The study varied the size of virtual impactors and tested two primary internal structures for Psyche:
- Layered Structure: A metallic core surrounded by a thin, rocky mantle, suggesting formation from a violent collision that stripped away outer layers.
- Uniform Mixture: A blend of metal and silicate, potentially created by a catastrophic impact that homogenized materials, similar to some metal-rich meteorites.
Role of Porosity in Crater Formation
A key finding from the research highlights the significant influence of porosity—the amount of empty space within the asteroid—on crater formation. The study indicated that porosity, often excluded from previous models due to its complexity, affects the impact process and the resulting crater shape. In asteroids with higher internal porosity, impact energy is absorbed more efficiently, leading to the formation of deeper, steeper craters and a reduced amount of ejected material.
Comparing these simulated crater characteristics with future spacecraft observations can assist scientists in determining if Psyche's interior has distinct layers of metal and rock or a more uniform mixture.
Adeene Denton, a postdoctoral researcher and co-author, noted the significance of incorporating porosity for realistically simulating impacts into unique asteroid types.
Simulation Results and Implications
The simulations determined that an impactor approximately three miles across would create a crater matching the known dimensions. The formation of this crater was found to be consistent with both the layered and the uniform mixed composition scenarios for Psyche. The inclusion of porosity in these models demonstrated its substantial effect on crater depth, shape, and the distribution of ejected material.
Erik Asphaug, a professor at LPL and co-author, noted that while the cores of planets like Earth or Mars are inaccessible, an exposed core of an early asteroid, if Psyche proves to be one, could provide insights into planetary evolution.
Future Interpretations for NASA's Psyche Mission
The NASA Psyche spacecraft carries instruments designed to study the asteroid's surface, gravitational field, magnetic field, and chemical composition. The simulations offer predictions that extend beyond crater shapes, including density variations caused by internal compression from impacts and the potential distribution of metal-rich debris across the surface. These predictions are expected to provide initial insights for the mission's geochemists, geologists, and modelers in interpreting the data collected upon the spacecraft's arrival.
The Psyche mission is led by Arizona State University and managed by NASA's Jet Propulsion Laboratory. Maxar Technologies (now Intuitive Machines) provided the spacecraft chassis. Psyche is designated as the 14th mission in NASA's Discovery Program.