GULLIES ON CERES? EXTENDING THE HYPOTHESIS OF TRANSIENT, BRINE-MOBILIZED FLOWS ON VESTA TO ITS NEIGHBORING PROTOPLANET

Vesta and Ceres are two protoplanets in the asteroid belt explored by the Dawn mission in 2011-2018. On Vesta, incised curvilinear gullies, often ending in lobate deposits, are rare in comparison to the more common, and morphologically dissimilar, dry flow gullies (Scully+2015). Scully+2015 hypothesized that localized deposits of subsurface water ice (from an earlier generation of ice-rich impactors) were heated by impacts. This melted ice formed liquid water that was short-lived under an impact-induced transient atmosphere, flowing in a debris-flow-like process, incising curvilinear gullies and constructing lobate deposits within the newly-formed craters. Recent laboratory experiments have shown that the incorporation of salt, in particular NaCl, to form brine flows, and the formation of frozen lids on top of the flows (similar to terrestrial lava tubes) would support the formation of curvilinear gullies and lobate deposits (Poston+2024). No salts have been observed on Vesta, but the meteorites originating from Vesta contain chlorides and other elements that could perhaps be mobilized in aqueous conditions (e.g., Barrett+2019). Salts, especially chlorides, are abundantly available on Ceres (e.g., De Sanctis+2020), which, in combination with Ceres’ endogenous water ice (e.g., Fu+2017), could potentially facilitate the formation of curvilinear gullies and lobate deposits. There are lobate deposits in Ceres’ Haulani crater (Harish+2023). However, curvilinear gullies have been difficult to identify on Ceres, perhaps due to spatial resolution differences: the highest resolution Dawn global imaging data for Vesta, ~20 m/pixel, is slightly better than for Ceres, ~35 m/pixel, which is critical when the average width of curvilinear gullies is only ~30 m/pixel (Scully+2015). Here we will present results of our search for curvilinear gullies and lobate deposits in fresh and young Cerean impact craters, because fresh craters are where these features are identified on Vesta.

As one of Dr. Scully’s graduate school advisors, Prof. An Yin co-authored Scully+2015 and was a great supporter of using geomorphological analysis and terrestrial analogs to investigate this innovative proposed formation mechanism of curvilinear gullies and lobate deposits on Vesta. Our continued investigation of this topic is a part of his scientific legacy, for which we are grateful.