Emplacement and tectonic deformation of smooth plains in the Caloris basin, Mercury

Interpretation and analysis of planetary structures

“…The global horizontal contractional strain estimated from the cumulative length of the lobate scarps mapped in Mariner 10 images is w0.043%, corresponding to a decrease in the radius of Mercury of approximately w0.5 km (Watters and Nimmo, 2010). Previously unrecognized thrust fault scarps discovered in MESSENGER images indicate that this magnitude of global contractional strain (Watters et al, 1998) was underestimated (Solomon et al, 2008;Watters et al, 2009a). The additional cumulative length of all the mapped scarps in the Mariner 10 hemisphere increases the globally averaged contractional strain to 0.06%.…”

“…Contractional deformation is indicated by landforms called lobate scarps (in the planetary literature) that are the expression of surface-breaking thrust faults (e.g., Strom et al, 1975;Dzurisin, 1978;Melosh and McKinnon, 1988;Watters et al, 1998Watters et al, , 2004Watters and Nimmo, 2010). Images returned by MESSENGER are showing that lobate scarp thrust faults are globally distributed and are the dominant tectonic landform on Mercury (Solomon et al, 2008;Watters et al, 2009a).…”

“…In addition to lobate scarps discovered outside the hemisphere imaged by Mariner 10, MESSENGER revealed previously unrecognized thrust fault scarps in an area near the Mariner 10 subsolar point (see Solomon et al, 2008;Watters et al, 2009a). An example is shown in Fig.…”

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

“…Given that the Caloris basin interior plains are volcanic in origin [Watters et al, 2009], the material may have originally been enriched in incompatible elements such as K and Th. The position of Caloris basin near one of Mercury's hot poles, however, may have depleted the near-surface K but would have left the Th abundance comparatively unaltered.…”

Extent, age, and resurfacing history of the northern smooth plains on Mercury from MESSENGER observations

“…Although no diagnostic volcanic features or constructs were conclusively identified in the Mariner 10 images, possibly due to resolution and illumination limitations (Schultz, 1977;Malin, 1978;Milkovich et al, 2002), a volcanic origin for much of the smooth plains was favored on the basis of their widespread distribution, embayment relations with surrounding topography, visible color properties, relatively young age, and superposed tectonic features (e.g., Murray et al, 1974b;Strom et al, 1975b;Trask and Strom, 1976;Kiefer and Murray, 1987;Spudis and Guest, 1988;Robinson and Lucey, 1997;Robinson and Taylor, 2001). Although a volcanic origin for smooth plains on Mercury was called into question (Wilhelms, 1976;Oberbeck et al, 1977), and although it is certainly possible that some smooth plains deposits are impact-generated products (i.e., fluidized ejecta, impact melt), most regions of smooth plains are now interpreted as products of effusive volcanism, much like the lunar maria (Murray et al, 1974b;Murray, 1975;Trask and Guest, 1975;Strom et al, 1975b;Trask and Strom, 1976;Kiefer and Murray, 1987;Robinson and Lucey, 1997;Head et al, 2008Head et al, , 2009aHead et al, , 2011Murchie et al, 2008;Robinson et al, 2008;Solomon et al, 2008;Denevi et al, 2009Denevi et al, , 2013aErnst et al, 2010;Fassett et al, 2009;Kerber et al, 2009Kerber et al, , 2011Watters et al, 2009Watters et al, , 2012Prockter et al, 2010;Freed et al, 20...…”