The NEO (175706) 1996 FG3 in the 2-4 μm spectral region: Evidence for an aqueously altered surface

We present observations of the binary near-Earth Asteroid (175706) 1996 FG3 in the 2-4 μm spectral region, obtained on multiple nights using the SpeX instrument on the NASA Infrared Telescope Facility (IRTF). We find evidence for an absorption band of ∼5-10% (depending on the night and details of continuum choice), diagnostic for hydrated/hydroxylated minerals on the asteroid surface. This demonstrates that the optical surface of 1996 FG3 has not been heated to dehydrating temperatures. Sample-return missions targeting 1996 FG3 will likely find relatively fresh areas for sampling.