2010 Pellas‐Ryder Award for Vishnu Reddy

Abstract

We are pleased to announce that this year the Pellas-Ryder Award for best student paper is given to Vishnu Reddy for his paper “Composition of 298 Baptistina: Implications for the K/T Impactor Link” (Meteoritics & Planetary Science 44: 1917–1927). The Pellas-Ryder Award is jointly sponsored by the Meteoritical Society and the Planetary Geology Division of the Geological Society of America, and recognizes the best planetary science paper of the year written by an undergraduate or graduate student. Vishnu was born and raised in India, and early on discovered an interest in planetary sciences. As an undergraduate student at Bharathiar University in India, he studied the nature of lunar rays around the crater Proclus, which gave him valuable experience in working with telescopes and imagers. At this time, he also developed an interest in observing near-Earth asteroids (NEAs) and comets. Because of the limited funding opportunities in India for carrying out planetary science research, he started a private foundation, Spaceguard India, and raised $6,000 to build an observatory for studying NEAs from India. His interest in carrying out astrometric observations continued after he joined the graduate program at the University of North Dakota’s Space Studies department, and he was able to discover 23 main belt asteroids, one of which was later named Bharat in honor of his home country. During his graduate studies at UND, he started to focus on photometric and spectroscopic observations of NEAs and main belt asteroids in order to carry out physical characterizations of these objects, working under the guidance of Dr. Mike Gaffey. His M.S. thesis consisted of mineralogical studies of olivine-rich asteroids. These asteroids are of considerable interest because the presence of nearly pure olivine provides evidence of extensive magmatic differentiation (melting and mineral separation) and the exposure of deep mantle material by collisional breakup of the parent body. Vishnu’s Ph.D. work focused on three main areas: (1) spectral calibrations of pyroxene mineralogies with the goal of using asteroid spectra to determine pyroxene chemistries in order to constrain formation temperatures of the parent bodies and the redox state of the solar nebula where the object formed; (2) physical characterization (composition, albedo, size and thermal properties) of NEAs for impact hazard assessments; and (3) the relationship of the Baptistina asteroid family to the K-T impactor. In 2007, Bottke et al. (Nature 449: 48–53) suggested that the impactor responsible for the K-T extinction of the dinosaurs 65 Ma was a member of the Baptistina asteroid family, created when the parent body of asteroid 298 Baptistina (and its family) was catastrophically disrupted ∼160 Ma. A key part of this link was based on the identification of 298 Baptistina as a CM2 carbonaceous chondrite-like asteroid (e.g., a C- or X-type classification). However, Vishnu and his advisor noted that the visible spectrum of 298 Baptistina lacked evidence of a weak absorption feature characteristic of the hydrated silicates in CM2 assemblages, but instead showed evidence of a weak 0.90-μm band, suggesting that the surface of the asteroid was dominated by anhydrous silicates. Vishnu initiated further spectral observations of 298 Baptistina using the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatiory in Hawai’i in order to verify this signature. He also organized a group of investigators interested in this asteroid, including Bottke himself, and thereby turned a potentially confrontational activity into a collaborative effort. The near-IR and thermal IR spectra obtained showed that 298 Baptistina has moderately strong absorption features indicating the presence of the anhydrous silicate minerals olivine and pyroxene, and that it has a moderately high albedo, much higher than a CM2 assemblage. These observations clearly showed that 298 Baptistina was not a C-type asteroid, but an S-type one, and therefore not consistent with CM2-type carbonaceous chondrite material. Ongoing observations of other members of the Baptistina asteroid family suggest that CM2-type materials are not a significant component of these bodies. Vishnu’s work therefore shows that, if the K-T impactor was indeed a CM2 or similar type body, then it was almost certainly not derived from the Baptistina family. In closing, I would like to join with the officers and members of the Meteoritical Society and the Planetary Geology Division of the Geological Society of America, as well as the competition judges, in congratulating Vishnu Reddy. His work stood out in a field of strong papers and his exemplary research approach attests to the high standards attained by students in planetary science.