Mercury

Identification and measurement of neutron-absorbing elements on Mercury’s surface

“…Taylor and Scott (2003) provided estimated compositions for three different models: a refractory-volatile mixture model (Morgan and Anders, 1980), a metal-rich chondrite model, and a partial melt composition based on an enstatite chondrite bulk composition (McCoy et al, 1999). The R a values for these models are R a = 39 Â 10 À4 , 34 Â 10 À4 , and 22 Â 10 À4 cm 2 /g, respectively.…”

“…Second, although other elements do have microscopic absorption cross sections as high or higher than Fe and Ti (2.59 b and 6.11 b, respectively), such as 35 Cl (r a = 44 b), 63 Cu (r a = 4.47 b), 55 Mn (r a = 13.4 b), and 58 Ni (r a = 4.6 b), it is not expected in non-hydrated, silicate planetary materials that the abundances of these or other such elements would be as high as the few weight percent required to measurably affect R a . For example, 4-5 wt.% of MnO, which has the largest r a of the other elements listed above, is required in the model compositions of Taylor and Scott (2003) to increase R a to the medium range of our measured R a values, but such an abundance would be almost two orders of magnitude larger than the values given by Taylor and Scott (2003). While such high values of Mn (and other similar elements) cannot be completely ruled out, they are unlikely to apply to large parts of Mercury's surface.…”

“…Despite many measurements from Earth and from the Mariner 10 spacecraft, there is little definitive information about the elemental composition of Mercury's surface (Goettel, 1988;Taylor and Scott, 2003). Specifically, there has been much debate about the Fe content of Mercury's surface materials (e.g., Sprague et al, 2007;Boynton et al, 2007).…”

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

“…Some volatile elements (K and S) are not depleted and the low FeO content of the surface points to highly reduced conditions (Wadhwa, 2008; Zolotov, 2011;McCubbin et al, 2012). This suggests that chondritic materials are probably the building blocks of the planet, possibly either enstatite chondrite or bencubbinite (Wasson, 1988;Taylor and Scott, 2003;Malavergne et al, 2010).…”

Depth of faulting and ancient heat flows in the Kuiper region of Mercury from lobate scarp topography

“…where p is the density, g is the acceleration due to the gravity (3.7 m 5-2 for Mercury), z is the depth and ex is a coefficient depending on the stress regime (which is 3 for pure compression, appropriate for thrust faulting; e.g., Ranalli, 1997 (Peplowski et al, 2011), and we estimated U abundance by assuming the chondritic ThjU ratio of 3.6 (Morgan and Anders, 1980;Taylor and Scott, 2005). Therefore, the used crustal heat production rates range between 1.7 x 10-4 and 8.7 x 10-4 mW m-3 at the time of scarp formation.…”