High manganese concentrations in rocks at Gale crater, Mars

Abstract

The surface of Mars has long been considered a relatively oxidizing environment, an idea supported by the abundance of ferric iron phases observed there. However, compared to iron, manganese is sensitive only to high redox potential oxidants, and when concentrated in rocks, it provides a more specific redox indicator of aqueous environments. Observations from the ChemCam instrument on the Curiosity rover indicate abundances of manganese in and on some rock targets that are 1-2 orders of magnitude higher than previously observed on Mars, suggesting the presence of an as-yet unidentified manganese-rich phase. These results show that the Martian surface has at some point in time hosted much more highly oxidizing conditions than has previously been recognized.

ChemCam activities and discoveries during the nominal mission of the Mars Science Laboratory in Gale crater, Mars

“…The accuracy scales with the abundances. 41 Nickel is challenging to detect in geological materials with LIBS. The most important lines are at 301.28 nm, around 305 nm, and at 309.35, 310.27 and 313.5 nm (Fig.…”

“…8) because the target is unusually shiny and smooth. 41 The surface is also clear of dust aer a few shots. The image resolution is $30 mm per pixel.…”

“…In the rst 360 Sols of the mission, $3% of rock targets analyzed by ChemCam contained Mn abundances that were at least three times the average Martian basalt value of 0.4 wt% MnO based on previous in situ measurements, 57 suggesting the presence of a high-Mn mineral phase. 41 One target named Caribou (observed on Sol 342) had a single analysis location containing MnO in excess of 60 wt%, the highest observed on Mars to date. 41 Not all of the high-Mn observations have a clear geological context (e.g., mineral grains, or a depositional environment), but in at least one location it appears that Mn concentrations occur primarily as Mn-oxide veins that ll fractures within a sandstone.…”

“…41 One target named Caribou (observed on Sol 342) had a single analysis location containing MnO in excess of 60 wt%, the highest observed on Mars to date. 41 Not all of the high-Mn observations have a clear geological context (e.g., mineral grains, or a depositional environment), but in at least one location it appears that Mn concentrations occur primarily as Mn-oxide veins that ll fractures within a sandstone. ChemCam observations at the Dillinger outcrop on Sols 606-630 found thin layers of high Mn on three erosion-resistant n-like features, which appear throughout the outcrop and are interpreted as post-depositional fracture lls.…”

Gale crater and impact processes – Curiosity’s first 364 Sols on Mars

“…Otherwise, only a few small hints of enrichments of lithium in some spots in the Bathurst_Inlet outcrop and the Rocknest_3 outcrop have been observed during the first 363 Sols . There may be some evidence for hydrothermal fluids from enrichments of Mn that have been documented in what appear to be exposed fracture fills; however, these fills crosscut and therefore postdate the Gale sediments and the origin of the fluids that concentrated and deposited Mn here are as of yet unknown (Lanza et al, 2014).…”