The James Webb Space Telescope has measured dust around young stars whose chemistry points to planet-shattering collisions, the same kind of giant impact thought to have formed our Moon.
What Webb and archival Spitzer observations of 21 extreme debris disks suggest about collisions between Moon- and Mars-sized bodies, and what remains uncertain.
0:00 A collision that made a Moon?
0:37 What Webb actually saw
1:47 How rocky planets are built
2:35 A rare kind of disk
3:31 Three family traits
4:11 Reading the glass: silica
5:19 Not the first clue
6:29 Scars close to home: Mercury and Uranus
7:17 Our Moon's possible story
8:16 What this does not show
8:56 The question
What is measured: Webb's MIRI instrument (16 systems) and archival Spitzer data (5 systems) show these disks have unusually small, heated dust grains rich in silica and crystalline minerals, lots of warm dust, and irregular brightness changes. What is interpreted: that the dust comes from large collisions; that silica-rich disks (8 of 21) record high-energy impacts between Mars-sized bodies and silica-poor ones (13 of 21) smaller or grazing impacts. Webb did not photograph a collision. The Moon-forming "Theia" impact is the leading explanation, not a proven one; the 2022 NASA/Durham simulation shown is one possible outcome.
Sources
- NASA: "NASA's Webb Provides Crash Course on Planet-Shattering Collisions" (1 Oct 2026); ESA/Webb weic2618
- Su et al., "Extreme Debris Disks: Insights into Violent Collisions in Planet Formation and Destruction", The Astrophysical Journal (2026), arXiv:2607.06684
- NASA Ames / Durham University Moon-origin simulation, Kegerreis et al., ApJ Letters (2022)
- Lisse et al. (2009) on HD 172555 (Spitzer); NASA Spitzer binary-star collisions (2010); NASA RZ Piscium (2017)
- NASA Webb MIRI cryocooler; terrestrial planet formation (PNAS 2011); Mercury and Uranus impact hypotheses (MESSENGER; Kegerreis 2018)
Visuals: NASA, ESA, CSA, J. Olmsted (STScI) — Webb artwork and data graphic; NASA Ames / Durham University simulation; NASA/JPL-Caltech (Spitzer artist concepts, MIRI cryocooler photo, Voyager 2); NASA/JHUAPL/Carnegie (MESSENGER); NASA Goddard Scientific Visualization Studio; Webb "Cosmic Cliffs" NASA, ESA, CSA, STScI. Simulations, artist concepts and examples are labelled on screen.
Narration is a synthetic voice. Independent production, not affiliated with or endorsed by NASA, ESA or CSA.
If you could point Webb at one of these dusty systems for a year, what would you most want to learn? Tell us in the comments.
