2011 Pellas‐Ryder Award for Andrew W. Beck

Abstract

We are pleased to announce that this year the Pellas-Ryder Award for Best Student Paper is given to Andrew William Beck for his paper “Diogenites as polymict breccias composed of orthopyroxenite and harzburgite” (Beck A. W. and McSween H. Y., Jr. 2010. Meteoritics & Planetary Science 45:850–872). 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. Andrew grew up in Granville, Ohio, and graduated cum laude from Albion College in 2004 with a Bachelor of Arts degree in philosophy and a minor in geology. He then spent two additional years at Albion, working as a geological sciences technician and teaching assistant. During this time he collaborated with faculty and students on research projects ranging from fluvial geomorphology to vertebrate paleontology, and assisted in teaching undergraduate laboratory classes. During the summer of 2008 he was an assistant instructor at Albion’s geology field camp, where he helped students with mapping projects in a variety of geologic terranes throughout South Dakota and Wyoming, and instructed them in geologic field methods and advanced electronic mapping techniques (ArcGIS). In 2006 Andrew started graduate work at the University of Tennessee in Knoxville, under the supervision of Professor Hap McSween; he will obtain his Ph.D. in the summer of 2011. His doctoral research has focused on understanding geologic processes acting in the early solar system through investigation of achondritic meteorites from differentiated parent bodies. Diogenites are ultramafic members of the HED (howardite-eucrite-diogenite) suite of meteorites generally thought to come from the asteroid 4 Vesta. Examination of the petrology and geochemistry of these rocks, and comparison with analogous terrestrial ultramafic terranes, can provide constraints on the processes taking place within the interior of their parent body. Most diogenites consist predominantly of orthopyroxene with minor amounts of other minerals and are traditionally thought to have crystallized from magmas in the lower crust of the parent asteroid. A few olivine-rich diogenites also exist and were originally interpreted as having a distinct origin as depleted peridotite residues from the mantle remaining after melt extraction. However, observations that some sections of olivine diogenites did not contain more olivine than normal diogenites, and that orthopyroxene compositions were similar in both types of diogenites, suggested the possibility of a closer petrogenetic relationship between the two types of meteorites than previously assumed. In the work for which Andrew Beck is receiving the Pellas-Ryder Award, he carries out a systematic study of the occurrence of olivine in both normal and olivine diogenites and investigates the relationship of olivine-rich diogenites to the rest of the HED meteorites. Andrew’s study shows that olivine in diogenites is exclusively associated with magnesian orthopyroxene, with which it is in chemical equilibrium. A second category of diogenite contains ferroan orthopyroxene and minor plagioclase, but no olivine. Trace element variations indicate that both types of diogenite probably formed by fractional crystallization in multiple plutons with varying source compositions emplaced within the crust of the parent body. This implies that the asteroid 4 Vesta may not have a uniform lower crustal layer, as previously assumed. Based on these observations, Beck and McSween (2010) also propose reclassification of all ultramafic meteorites from the HED parent body as diogenites, with prefixes of “dunitic” (≥90% olivine), “harzburgitic” (olivine + orthopyroxene), and “orthopyroxenitic” (≥90% orthopyroxene) to distinguish the three different lithologies present. Andrew has won several awards and recognitions in his graduate career to date, including a Mayo Educational Foundation grant for studies in mineralogy, two Professional Promise awards, an Outstanding Graduate Student award and an Outstanding Student Presentation award from the Earth and Planetary Sciences department at the University of Tennessee. His work on the ultramafic HED meteorites and recognition that there are two distinct kinds of diogenite, an observation overlooked in past studies of these meteorites, represent a major discovery, providing constraints on the composition of the lower crust of the HED parent body, and with important implications for analysis of the spectroscopic data obtained from the Dawn spacecraft mission to 4 Vesta. In closing, the members of the Pellas-Ryder Award Committee would like to join the officers and members of the Meteoritical Society and the Planetary Geology Division of the Geological Society of America in congratulating Andrew Beck. His work stood out in a field of strong papers and his exemplary research attests to the high standards attained by students in planetary science.