New insights into gully formation on Mars: Constraints from composition as seen by MRO/CRISM

Abstract

Over 100 Martian gully sites were analyzed using orbital data collected by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and High Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter (MRO). Most gullies are spectrally indistinct from their surroundings, due to mantling by dust. Where spectral information on gully sediments was obtained, a variety of mineralogies were identified. Their relationship to the source rock suggests that gully‐forming processes transported underlying material downslope. There is no evidence for specific compositions being more likely to be associated with gullies or with the formation of hydrated minerals in situ as a result of recent liquid water activity. Seasonal CO2 and H2O frosts were observed in gullies at middle to high latitudes, consistent with seasonal frost‐driven processes playing important roles in the evolution of gullies. Our results do not clearly indicate a role for long‐lived liquid water in gully formation and evolution.

The formation of gullies on Mars today

“…May be proxy for other favorable conditions; thermophysical classes correlate with latitude. Gullies are not routinely associated with hydrated minerals (Núñez et al, 2016). Consistent with no frequent or long-lived water-rock interactions.…”

Martian gullies: a comprehensive review of observations, mechanisms and insights from Earth analogues

“…Harrison et al (2017) found that fans associated with active gullies in Gasa Crater have higher thermal inertia than other gully fans, yet lower thermal inertia than talus slopes. The hysperspectral imaging system CRISM has been used to examine the composition of the materials in and around gullies Stepinski, 2018, 2017;Barnouin-Jha et al, 2008;Núñez et al, 2016a) and suggested that: (1) gullies are hosted on a wide range of geological materials, (2) in some cases gullies expose underlying rock and move it downslope, (3) many other gullies show no spectral difference from their surroundings and (4) there is no systemtic association between hydrated minerals and gullies even in the new light-toned deposits near gullies. Heldmann et al (2010) used CRISM data and also confirmed that recent light-toned deposits in Penticton Crater have no spectral differences to surrounding material.…”

Time will tell: temporal evolution of Martian gullies and palaeoclimatic implications

“…Gully growth may be limited by: (a) decreasing geomorphological activity in gullies over time following crater formation [De Haas et al, 2015c], (b) the latitude-dependent mantle acting as a barrier to bedrock-incision and enlargement once established [De Haas et al, 2015c], (c) alternating erosional/depositional episodes driven by orbital cycles [Dickson et al, 2015] or (d) a combination of these factors. Additionally, we know that some gully-fans are fed by alcoves that cut into bedrock [e.g., Johnsson et al, 2014;De Haas et al, 2015c;Núñez et al, 2016] while other gully-fans are fed by alcoves cutting into LDM or glacial deposits [e.g., Head et al, 2008;Conway and Balme, 2014;Núñez et al, 2016], which may be related to the evolution of the host-crater wall over time.…”