Detection of new asteroids with JWST MIRI: Solar System science and planetary defence

Asteroids are remnants of the early Solar System and are possible reservoirs of organic compounds that can be delivered to planets. Besides, collisions with asteroids can alter the evolution of planets and their moons and pose a threat to life on Earth. We will present our project on detecting and characterising asteroids via their thermal emission using the JWST Mid-Infrared Instrument (MIRI) in the context of Solar System science and planetary defence. JWST MIRI opened up a new window to detect small and cool asteroids by observing at mid-infrared wavelengths (5 - 28 micron) with unprecedented sensitivity. After four years in operation, a wealth of archival MIRI imaging data is available for mining. As a first step, we focused on the images acquired via the MIRI Mid-INfrared Disk Survey (MINDS) which is part of the MIRI European Consortium Guaranteed Time Observation program. We detected 18 asteroids in this data set. Most of them were unknown, and these are fainter and smaller than the known ones. We will present our method to search for asteroids, show the results obtained so far, and describe our plan to extend it to the whole MIRI archive. One component will be to develop a citizen science project to identify asteroids. This search is complementary to those conducted at visible and near-infrared wavelengths with facilities such as VST/OmegaCAM, HST, Euclid, and LSST: their combination helps build the spectral energy distribution of asteroids which constrain their temperatures, sizes, and surface properties. Overall, this study will help understand the physical properties of asteroids, their role in the formation of the Solar System and of planetary systems in general, and will contribute to assessing the risk of future collisions with Earth.