Characterizing Primitive Asteroids

In this project, we will reduce and analyze STIS spectra of six low-albedo class asteroids: 24 Themis, 372 Palma, 65 Cybele, 143 Hilda, 1144 Oda and 279 Thule, collected with the G230L and G430L gratings (one visit per target observations with the G230L and G430L gratings in each orbit). We will utilize existing software (e.g., stistools) to check the calibration of the STIS spectra collected with the MAMA and CCD gratings and extract the 12 calibrated STIS spectra. We will join the spectra collected with the G230L and G430L in each of the visits, using their overlapping wavelength coverage between 290 and 318 nm, thereby generating six finalized spectra that span ~160 to 570 nm. We will scale the joined G230L+G430L spectra to their published visible geometric albedos. We will carefully inspect the spectra to determine whether any absorption features are present; in particular in the B-class asteroids (Themis and Palma), rather noisy IUE observations of other B-class asteroids have suggested the presence of an absorption feature centered near 250 nm, and if so, compare with laboratory data to try to understand its origin. We will assess whether the P- and D-type asteroids show UV spectral features connected with organics. We will study the overall spectral shapes (e.g. spectral slopes in various regions of the spectra, location of any UV dropoff) to understand whether spectra can potentially be linked to hydration and/or location in the main belt.