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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 17, 1909, doi:10.1029/2003GL017907, 2003

The first detection of water absorption on a D type asteroid

Ai Kanno

Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan


Takahiro Hiroi

Department of Geological Sciences, Brown University, Providence, Rhode Island, USA


Ryosuke Nakamura

Lunar Mission Research Center, National Space Development Agency of Japan, Tsukuba, Japan


Masanao Abe

Research Division for Planetary Science, Institute of Space and Astronautical Science, Sagamihara, Japan


Masateru Ishiguro

Research Division for Planetary Science, Institute of Space and Astronautical Science, Sagamihara, Japan


Sunao Hasegawa

Research Division for Planetary Science, Institute of Space and Astronautical Science, Sagamihara, Japan


Seidai Miyasaka

Tokyo Metropolitan Government, Tokyo, Japan


Tomohiko Sekiguchi

Division of Radio Astronomy, National Astronomical Observatory of Japan, Mitaka, Japan


Hiroshi Terada

Subaru Telescope, National Astronomical Observatory of Japan, Hilo, Hawaii, USA


George Igarashi

Laboratory for Earthquake Chemistry, The University of Tokyo, Tokyo, Japan


Abstract

The D type asteroids are among the darkest objects known in our solar system. Here, we present infrared spectra of one of the main-belt D type asteroids, 773 Irmintraud. In contrast to previous observations of D type asteroids, we found a gap of reflectance around 3 μm in wavelength. The 3 μm gap is one of the spectral signatures of OH or H2O as water ice or in hydrous minerals, which had formed in the processes of aqueous alteration in the early solar system. We suggest that D type asteroids, which are all the while considered as unaltered primitive material, could be aqueously altered. Our data do support the presence of water on a compositionally primitive D type asteroid.

Received 5 June 2003; accepted 30 July 2003; published 12 September 2003.

Index Terms: 6008 Planetology: Comets and Small Bodies: Composition; 6020 Planetology: Comets and Small Bodies: Ice; 6040 Planetology: Comets and Small Bodies: Origin and evolution; 6045 Planetology: Comets and Small Bodies: Physics and chemistry of materials; 6055 Planetology: Comets and Small Bodies: Surfaces and interiors.

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Citation: Kanno, A., T. Hiroi, R. Nakamura, M. Abe, M. Ishiguro, S. Hasegawa, S. Miyasaka, T. Sekiguchi, H. Terada, and G. Igarashi (2003), The first detection of water absorption on a D type asteroid, Geophys. Res. Lett., 30(17), 1909, doi:10.1029/2003GL017907.