The unique geomorphology and physical properties of the Vestalia Terra plateau

Abstract

a b s t r a c tWe produced a geologic map of the Av-9 Numisia quadrangle of asteroid Vesta using Dawn spacecraft data to serve as a tool to understand the geologic relations of surface features in this region. These features include the plateau Vestalia Terra, a hill named Brumalia Tholus, and an unusual ''dark ribbon'' material crossing the majority of the map area. Stratigraphic relations suggest that Vestalia Terra is one of the oldest features on Vesta, despite a model crater age date similar to that of much of the surface of the asteroid. Cornelia, Numisia and Drusilla craters reveal bright and dark material in their walls, and both Cornelia and Numisia have smooth and pitted terrains on their floors suggestive of the release of volatiles during or shortly after the impacts that formed these craters. Cornelia, Fabia and Teia craters have extensive bright ejecta lobes. While diogenitic material has been identified in association with the bright Teia and Fabia ejecta, hydroxyl has been detected in the dark material within Cornelia, Numisia and Drusilla. Three large pit crater chains appear in the map area, with an orientation similar to the equatorial troughs that cut the majority of Vesta. Analysis of these features has led to several interpretations of the geological history of the region. Vestalia Terra appears to be mechanically stronger than the rest of Vesta. Brumalia Tholus may be the surface representation of a dike-fed laccolith. The dark ribbon feature is proposed to represent a long-runout ejecta flow from Drusilla crater.

Geologic mapping of ejecta deposits in Oppia Quadrangle, Asteroid (4) Vesta

“…Albalonga Catena is characterized by a series of pits with an east-west alignment and is referred to as a pit chain. What is unique about this feature is that it begins as a series of merged pits in the east, but transitions to a topographic high known as Brumalia Tholus on Vestalia Terra at the western end of the lineament (De Sanctis et al, 2014;Buczkowski et al, 2014). A detailed discussion on the origin of this feature is presented in Buczkowski et al (2014).…”

“…7). To the west, is Numisia quadrangle Av-9, which is dominated by ancient cratered highland feature, Vestalia Terra (Buczkowski et al, 2014). To the east are Gegania quadrangle Av-6 and Lucaria quadrangle Av-7, where troughs in the Divalia Fossae Formation are best preserved (Schäfer et al, 2014).…”

“…Feralia Planitia is a topographic basin that is bound to the west by Vestalia Terra (Av-9) (De Sanctis et al, 2014; Buczkowski et al, 2014), the rim of Rheasilvia to the south (Av-14) (Williams et al, 2014a), Divalia Fossae troughs (Av-6) to the east and cratered highland terrain (Av-5) to the northeast (Ruesch et al, 2014;Schäfer et al, 2014;Scully et al, 2014) (Figs. 2 and 3).…”

“…Based on studies of the Howardite-Eucrite-Diogenite (HED) clan of meteorites, Vesta is a differentiated body (e.g., McCord et al, 1970;McSween et al, 2013). Basaltic compositions imply that there was once volcanic activity on the surface (Wilson and Keil, 1996), but evidence of volcanic activity is not apparent on the surface (Yingst et al, 2014, in press) except in a few potential locations where anomalous topographic mounds are present (e.g., Brumalia Tholus in Av-9) (e.g., Buczkowski et al, 2014). The topography of Vesta varies in elevation between À22.3 and 19.1 km (reference ellipsoid 285 km  229 km) (Jaumann et al, 2012).…”

Introduction: The geologic mapping of Vesta

“…Williams et al (2014) focus on the stratigraphic relations of the large, young fresh craters and associated dark ejecta field found in the Av-8 (Marcia) quadrangle, and Buczkowski et al (2014) focus on the diversity of units on the highland of Vestalia Terra in Av-9 (Numisia) quadrangle. Garry et al (2014) have used the geologic map of the Av-10 (Oppia) quadrangle to investigate the stratigraphic relations and the context of high-albedo crater ejecta surrounding Oppia crater, building on the study of Le Corre et al (2013).…”