Style and intensity of hydration among C-complex asteroids: A comparison to desiccated carbonaceous chondrites

• Published in: Icarus (New York, N.Y. 1962) Vol. 348; p. 113826
• Main Authors: Potin, S., Beck, P., Usui, F., Bonal, L., Vernazza, P., Schmitt, B.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.09.2020; Elsevier
• Subjects: Asteroids; Astrophysics; Meteorites; Physics; Spectroscopy; Surfaces; Thermal alteration; Surfaces; Spectroscopy; Meteorites; Thermal alteration; Asteroids
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2020.113826

Here we report a comparison between reflectance spectroscopy of meteorites under asteroidal environment (high vacuum and temperature) and Main Belt and Near Earth Asteroids spectra. Focusing on the –OH absorption feature around 3 μm, we show that the asteroidal environment induces a reduction of depth and width of the band, as well as a shift of the reflectance minimum. We then decompose the –OH feature into several components with a new model using Exponentially Modified Gaussians. Unlike previous studies, we confirme the link between these components, the aqueous alteration history and the amount of water molecules inside of the sample, using the shape of this spectral feature only. We then apply this deconvolution model to asteroids spectra which were obtained with a space-borne telescope and two space probes, and find a strong similarity with the components detected on meteorites, and among asteroids from a same type. Based on the conclusions drawn from our meteorites experiment, we suggest to use the 3-μm band as a tracer of the alteration history of the small bodies. Using the 3-μm band only, we show that Ryugu has been heavily altered by water, which is consistent with its parent body being covered with water ice, then went through a high temperature sequence, over 400 °C. We also point out that the 3-μm band of Bennu shows signs of its newly discovered surface activity. •Exponentially Modified Gaussians are used to model the shape of the 3-μm band.•The components of the band depend on the aqueous alteration and relative humidity.•Similar components are detected on the asteroids spectra.•The components are used to retrieve the alteration history of the asteroids.•Signs of activity on Bennu and two Cgh-types are detected through the –OH band.