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Ejecta from Dimorphos following the DART mission impact, significantlyincreased the brightness of the Didymos-Dimorphos system, allowing us toexamine sub-surface material. We report daily near-IR spectroscopicobservations of the Didymos system using NASA's IRTF, that follow the evolutionof the spectral signature of the ejecta cloud over one week, from one daybefore the impact. Overall, the spectral features remained fixed (S-typeclassification) while the ejecta dissipated, confirming both Didymos andDimorphos are constructed from the same silicate material. This novel resultstrongly supports binary asteroid formation models that include breaking up ofa single body, due to rotational breakup of km-wide bodies. At impact time +14and +38 hours, the spectral slope decreased, but following nights presentedincreasing spectral slope that almost returned to the pre-impact slope.However, the parameters of the $1~\mu m$ band remained fixed, and no "fresh" /Q-type-like spectrum was measured. We interpret these as follow: 1. The ejectacloud is the main contributor ($60-70\%$) to the overall light during the$\sim40$ hours after impact. 2. Coarser debris ($\geq 100~\mu m$) dominated theejecta cloud, decreasing the spectral slope (after radiation pressure removedthe fine grains at $\leq10$ hours after impact); 3. after approximately oneweek, the ejecta cloud dispersed enough to make the fine grains on Didymossurface the dominating part of the light, increasing the spectral slope topre-impact level. 4. a negligible amount of non-weathered material was ejectedfrom Dimorphos' sub-surface, suggesting Dimorphos was accumulated fromweathered material, ejected from Didymos surface.

Near-IR Spectral Observations of the Didymos System -- Daily Evolution Before and After the DART Impact, Indicates Dimorphos Originated from Didymos