The global distribution of pyroclastic deposits on Mercury: The view from MESSENGER flybys 1–3

Phase equilibria of ultramafic compositions on Mercury and the origin of the compositional dichotomy

“…While some pyroclastic deposits have been emplaced during explosive eruption due to decompression and expansion of volatiles (Kerber et al, 2011), most eruptions have formed plains with broad, thick flow fronts . Calculations of viscosities (Giordano et al, 2008) for surface lavas at the liquidus temperature, 1450 1C for Group 1 and 1380 1C for Group 2, range from 0.8 to 13.5 Pa s which is at the lower limit of any silicate melt measured (Table 1).…”

“…Strom et al, 1975;Robinson and Lucey, 1997) revealed plains materials whose origin was debated, and not until additional, higher resolution images were acquired by the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft did it become apparent that surface volcanism was widespread and produced kilometer-thick deposits (Head et al, 2008. Many pyroclastic deposits have also been identified (Rava and Hapke, 1987;Kerber et al, 2011). The crater deficiency of Mercury compared to the Moon even suggests that most of its surface has been volcanically resurfaced by intercrater plain emplacement (Fassett et al, 2011(Fassett et al, , 2012.…”

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...…”

Phase-ratio images of the surface of Mercury: Evidence for differences in sub-resolution texture

“…Of particular interest for Mercury are hollows (Blewett et al, , 2013Thomas et al, 2014), pyroclastic deposits (Head et al, 2008;Kerber et al, 2011;Goudge et al, 2014), and a prominent flow of dark impact melt (Klima et al, 2011;D'Incecco et al, 2013). A brief description of the features considered in this report is given in the next section.…”