Mid-IR spectrum of Ryugu sample C0137 compared to in-situ data and carbonaceous chondrites

Abstract

The Near-Earth Asteroid (162173) Ryugu has been investigated by the JAXA Hayabusa2 mission [1]. Hayabusa2 successfully returned samples from two sites of Ryugu’s surface to Earth in December 2020[2]. Part of this mission was the deployment of the MASCOT lander [3] which studied Ryugu’s surface in detail. Ryugu is a rubble-pile asteroid covered in boulders and large pebbles [4-6]. Observations in the visible and near-infrared wavelength range indicate that Ryugu is as dark as any measured meteorite samples and that the closest match is thermally metamorphosed carbonaceous chondrites [6,7]. Although Hayabusa2 did not carry a dedicated thermal infrared spectrometer, the MARA instrument on the MASCOT lander observed a single boulder of the most common type on the surface of Ryugu through six channels with different filters, two broadband filters and four narrowband filters from 5.5-7 μm (B06), 8 – 9.5 μm (B08), 9.5 – 11.5 μm (B09), and 13.5 – 15.5 μm (B13)[8]. Here we compare the effective emissivity from MARA [9] with the infrared spectra of carbonaceous chondrite (CC) meteorite thin sections, remote-sensing spectra from Bennu, and the C0137 sample of Ryugu.