Mass movement on Vesta at steep scarps and crater rims

Abstract

a b s t r a c tThe Quadrangles Av-11 and Av-12 on Vesta are located at the northern rim of the giant Rheasilvia south polar impact basin. The primary geologic units in Av-11 and Av-12 include material from the Rheasilvia impact basin formation, smooth material and different types of impact crater structures (such as bimodal craters, dark and bright crater ray material and dark ejecta material). Av-11 and Av-12 exhibit almost the full range of mass wasting features observed on Vesta, such as slump blocks, spur-and-gully morphologies and landslides within craters. Processes of collapse, slope instability and seismically triggered events force material to slump down crater walls or scarps and produce landslides or rotational slump blocks. The spur-and-gully morphology that is known to form on Mars is also observed on Vesta; however, on Vesta this morphology formed under dry conditions.

The geology of the Marcia quadrangle of asteroid Vesta: Assessing the effects of large, young craters

“…Where possible, we have applied assessments of crater densities to obtain cratering model ages of crater units (Table 1) using both asteroid flux-based (Marchi et al, 2012a(Marchi et al, ,b, 2013; O'Brien et al, submitted for publication) and lunar-derived chronologies (Schmedemann et al, submitted for publication). Using crater statistics on Vesta is particularly challenging because of the abundance of highly sloped surfaces (Jaumann et al, 2012) and the large degree of degradation and modification of craters (see Krohn et al, 2014), such that homogeneous units are sometimes difficult to recognize.…”

The unique geomorphology and physical properties of the Vestalia Terra plateau

“…There is a bright layer evident in the sharp western wall, from which gullylike features consistent with dry granular flow (e.g. Shinbrot et al, 2004;Bart, 2007;Senthil Kumar et al, 2013;Scully et al, 2014;Krohn et al, 2014) seem to begin. However, upon closer examination these 'gullies' are the edges of mass-wasting lobes flowing down the crater wall (Fig.…”

Introduction: The geologic mapping of Vesta

“…This means that extremely steep slopes are common on Vesta compared with previously mapped terrestrial planets. These steep slopes may cause impact craters to be deformed into an asymmetric shape (see Krohn et al, 2014). Other craters can be partly buried by subsequent mass movements triggered by later impact events on Vesta's steep slopes.…”

“…Krohn et al (2014) use maps of Av-11 (Pinaria) and Av-12 (Sextilia) quadrangles to study Vesta's unusual asymmetric craters (sharp rims upslope, subdued rims downslope), while Kneissl et al (2014) investigate the ejecta of bright, mid-size, young craters and their contact with older basin units in Av-13 (Tuccia) quadrangle. Quadrangle maps of Av-14 (Urbinia) and Av-15 (Rheasilvia), which focus on ridged and grooved and central peak (respectively) units of the Rheasilvia Formation, are discussed in the paper by Yingst et al (in press), and are also included here as stand-alone maps ( Fig.…”