X‐Ray Amorphous Components in Sedimentary Rocks of Gale Crater, Mars: Evidence for Ancient Formation and Long‐Lived Aqueous Activity

The CheMin instrument on the Mars Science Laboratory rover Curiosity detected ubiquitous high abundances (∼15–70 wt%) of X-ray amorphous components (AmCs) in ancient sedimentary rocks Gale crater. Mechanisms and timing formation for AmCs are poorly constrained, could include volcanic, impact, or aqueous processes. We explore trends AmC composition abundance, look systematic compositional variation between sites within compositions were estimated indirectly based bulk chemistry nature abundance crystalline phases 19 rock samples. positively correlate with SiO2 contents, a mixing relationship appears to exist SiO2-rich FeOT-rich endmembers. Endmember inconsistent volcanic impact glass alone, so we conclude that FeOT contents formed largely through Cross-cutting relationships geologic context provide evidence most observed crater thus far may result from interactions localized fluids during late diagenesis. moderate low likely earlier (before soon after sediment deposition). Thus, represent mixtures materials over history crater, starting before first sediments deposited (late Noachian), ending well youngest lithified (at least mid-Hesperian). However, it remains unclear how these metastable minerals have persisted billions years diagenesis sediments.