Characteriizing Hydration in Asteroids from Observations in the Stratosphere with the BOPPS Infrared Camera

Abstract:

The Balloon Observation Platform for Planetary Science (BOPPS) mission is planning to observe several asteroids during its one-day mission in mid to late September, 2014. The observations of asteroids are secondary objectives designed to demonstrate the ability of the BIRC (BOPPS InfraRed Camera) to detect and characterize the extent of hydration on airless bodies. Hydrated asteroids are in part described by the presence of an infrared absorption band near 3-microns, due to the presence of OH complexed onto materials in their surfaces. This band is expected to begin near 2.6 microns, with a minimum between 2.7 and 2.8 microns based on laboratory measurements of vacuum desiccated carbonaceous meteorites materials [1]. Although this measurement is obscured in ground-based observations by the presence of water vapor in our atmosphere, the BOPPS mission will fly sufficiently high (~ 120K’) that telluric water absorptions will not be present potentially enabling precise identification of hydration features on airless bodies like asteroids. The BIRC measurements will be obtained with a cryogenic infrared camera equipped with a 9-position filter wheel with each infrared filter having a FWHM of ~ 3% of the center wavelength [2]. Six of these bands are selected to characterize the OH and H₂O absorption feature, and are centered at 2.45 microns, 2.73 microns, 2.85 microns, 3.05 microns, 3.2 microns, and 4 microns. The other three bands are at 0.67 microns (astronomical R-band), 4.27 microns, and 4.6 microns (these last two are to characterize CO₂ emissions from comets). The BOPPS mission plans to observe both 1Ceres and 4Vesta. Ceres has a strong water/hydroxyl band [3] whose position would be well characterized by this mission and has been reported to be a variable source of water vapor emission [4] . We will report initial results of BOPPS asteroid observations.

References: [1] Takir et al., (2013), Meteor. & Planet. Sci., 48, 9, 1618-1637; [2] Cheng et al., (2014), Fall AGU this session; [3] Rivkin et al., (2006), Icarus, 185, 563-567. [4] Kueppers et al. (2014) Nature 505, 525