Multiple sites of recent wet-based glaciation identified from eskers in western Tempe Terra, Mars

Precipitation in Mars' mid-latitudes formed Viscous Flow Features (VFFs), landforms analogous to terrestrial debris-covered glaciers, in the last 1 Gyr. Until recently, the prevailing view was that the Amazonian environment was not conducive to basal melting of VFFs. However, recent identification of VFF-linked eskers (sedimentary ridges deposited by meltwater in sub-glacial tunnels) in Phlegra Montes and Tempe Terra suggests localized basal melting has occurred. We identify two VFF-linked sinuous ridges in western Tempe Terra, which we propose are two additional eskers. To explore this hypothesis, we produce a 1:300,000 map of the geomorphology of western Tempe Terra, use impact crater counts to constrain the age of the sinuous ridges, and analyze the morphology and morphometry of the sinuous ridges. Mapping reveals a heavily deformed Noachian massif that was embayed by younger volcanic material and subsequently glaciated. The sinuous ridges lie 3–7 km from the VFF-termini and are associated with mounds which we interpret as ice-cored moraines. After considering multiple formation hypotheses (including inverted paleochannels and volcanic features) and comparing morphometries to Martian and terrestrial eskers, we suggest that both the sinuous ridges are of glacial origin and most likely eskers. This shows that basal melting of VFFs occurred at more than one location in Tempe Terra, at least transiently. Thus, our identification of two additional candidate eskers in Tempe Terra suggests that the late Amazonian thermal environment may have been more complex than previously thought and contributes to a better characterization of the recent glacial history of the region

Facet: The new user facility at SLAC

FACET (Facility for Advanced Accelerator and Experimental Tests) is a new User Facility at SLAC National Accelerator Laboratory. Its high power electron and positron beams make it a unique facility, ideal for beam-driven Plasma Wakefield Acceleration studies. The first 2 km of the SLAC linac produce 23 GeV, 3.2 nC electron and positron beams with short bunch lengths of 20 μm. A final focusing system can produce beam spots 10 μm wide. User-aided Commissioning took place in summer 2011 and FACET will formally come online in early 2012. We present the User Facility, the current features, planned upgrades and the opportunities for further experiments. Copyright © 2011 by IPAC'11/EPS-AG