Researchers infer collisions between Mars-size bodies from the composition of extreme debris disks around young stars. The findings, published in The Astrophysical Journal on October 1, 2026, draw on mid-infrared spectra from the James Webb Space Telescope (Webb) and archival observations from the Spitzer Space Telescope.
What the 21-disk sample contains
The researchers studied 21 extreme debris disks: five from Spitzer archival observations and 16 examined with Webb. Of the Webb observations, 12 were new and four followed up on systems previously examined by Spitzer.
These disks contain unusually high concentrations of warm dust, with smaller grains than those found in protoplanetary or typical debris disks. Their brightness also varies irregularly. Mid-infrared spectra reveal features that let researchers identify the disks’ composition and interpret what kinds of collisions may have produced the debris.
NASA estimates that about 1% of young stars show observable signs of this extreme-debris-disk phase, based on observations gathered so far.
Silica points to two possible collision regimes
About one-third of the disks in the sample are silica-rich. Researchers associate them with high-energy impacts between Mars-size bodies, in which rocky material may have vaporized. The roughly two-thirds that are silica-poor are associated with lower-energy, smaller-scale collisions, including grazing impacts between Moon-size objects.
These categories connect the dust’s composition with a likely impact regime. They offer clues to how rocky material behaves as young planetary systems form and evolve.
The disks’ ages and changing brightness
Silica-rich disks in the sample have so far been identified around stars younger than 300 million years. Silica-poor disks appear across a broader range of stellar ages and often show greater brightness variability. Just three disks in the sample fit the older-age criterion discussed by the researchers.
Researchers propose that changing orbits and further collisions could help explain how the debris and infrared brightness vary over time. That is a possible explanation for the patterns, rather than a demonstrated cause for every disk.
What the findings may say about the Moon
The disk patterns are consistent with the scenario in which a Mars-size body struck the early Earth and contributed material that formed the Moon. NASA also discusses a possible connection to the Late Heavy Bombardment as a hypothesis. The study places these ideas in the context of how rocky planets form and evolve.
