IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2022B026 PROGRAM_TITLE How dusty is the DART impact? Following Dimorphos' ejecta evolution PROGRAM_INV1 David Polishook PROGRAM_INV2 Andrew Rivkin PROGRAM_INV3 Cristina Thomas PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT near-Earth objects PROGRAM_ABSTRACT_BEG NASA's Double Asteroid Redirection Test [DART] provides a unique opportunity to study asteroids' interior. We propose to nightly follow the evolution of the ejecta cloud on the week after the impact [Sep 26 to Oct 2, HST], in order to put constraints on the amount of ejecta and to check if it covers the Didymos' surface, the parent body of the target Dimorphos. Didymos [thus, most probably Dimorphos too], has a thin 'weathered' surface [S-type spectrum], while below it, the ordinary chondrite material is 'fresh' [Q-type spectrum]. Dynamical models suggest that the impact will form an ejecta cloud that will be brighter than Didymos and Dimorphous together at the first couple of days after the impact. Afterwards, as the cloud dispersed, Didymos' surface will become again more dominant within the overall signal [the binary system and the ejecta cloud will not be resolved by IRTF]. Therefore, the level of weathering, as it reflects in the slope of the reflectance spectrum, might change within the week after the impact. If the total signal will appear fresh [low slope / Q-type] then change to weathered [high slope / S-type] after a few days, a significant amount of fresh dust dispersed without covering Didymos. If the spectrum will keep looking fresh, Didymos' surface is covered with Dimorphos ejecta. If the spectrum will have high slope through the entire week, the models of asteroid interior and strength, on which the predicted amount of excavated dust was calculated by, are wrong; or, if independent observations [through the spacecraft LiciaCube or ground-based photometry] will confirm a high level of ejecta, we can conclude that the ejecta is weathered, contradicting current models of space weathering. The asteroid is bright enough for a single hour of observations per night including overheads. PROGRAM_ABSTRACT_END