# # Program information file # PROGRAM_ID 2024B046 PROGRAM_TITLE Discovery of dynamic dust depletion in the innermost region of the protoplanetary disk of UX Tau A PROGRAM_INV1 Catherine Espaillat PROGRAM_INV2 Luisa Zamudio PROGRAM_INV3 Caeley Pittman PROGRAM_INV4 Thanawuth Thanathibodee PROGRAM_INV5 Michael Sitko PROGRAM_SCICAT extra-solar planets PROGRAM_ABSTRACT_BEG The timescale on which the inner region of protoplanetary disks is depleted sets the timescale for planet formation in the terrestrial planet-forming region. Terrestrial planet formation occurs in the innermost disk [i.e., within ~1 AU] which is currently inaccessible to imaging. However, the small dust grains can be probed by IR spectra. JWST has revealed dramatic MIR continuum variability in the protoplanetary disk of UX Tau A when compared to previous Spitzer observations, indicating that the small dust in the innermost disk has been significantly depleted while the outer disk remains unchanged. Here we propose for a total of about 3 nights with IRTF SpeX to follow up on these JWST observations. These additional SpeX observations will help us determine if this depletion is long-lived or if replenishment of the small dust in the inner disk is occurring. Together, these IRTF and JWST observations will determine the underlying physical mechanism driving this dramatic change in the innermost disk of UX Tau A, which will leave a lasting impact on studies of disk evolution. PROGRAM_ABSTRACT_END