JWST Spectra of 21 Extreme Debris Disks Identify Submicron Silica Grains from Moon-Mars Body Collisions

The study design combined archival Spitzer photometry with new JWST MIRI spectroscopy for a sample of 21 systems selected by stochastic infrared variability. Spectra were modeled for grain size, composition, and optical depth using radiative transfer codes, directly comparing mineralogy against protoplanetary disk templates. This approach isolates the signature of hypervelocity impacts that reset dust populations on timescales of years rather than steady-state grinding.

Results show EDDs contain grains smaller than 1 micron at fractions far exceeding typical debris disks, with silica features indicating flash heating above 1000 K. These properties distinguish EDDs as markers of late-stage dynamical instability, where giant-planet migration or scattering triggers Moon-Mars scale impacts during terrestrial planet assembly. The mineralogy matches predictions from hydrocode simulations of differentiated planetesimal collisions.

A key limitation is the modest sample size and reliance on infrared excess selection, which may miss fainter or edge-on systems. Larger JWST surveys combined with ALMA continuum imaging would strengthen causal links between observed dust and specific dynamical architectures.

Future observations can test whether EDD frequency declines sharply after 100 Myr, constraining the window of violent planet formation across stellar populations.