Ejecta deposits of Bakhuysen Crater, Mars

Bakhuysen Crater is a Late Noachian to Early Hesperian age similar to 150 km-diameter impact structure located in the heavily cratered southern highlands of Mars. It is one of the largest craters on Mars with well-preserved ejecta deposits. Impact ejecta deposits allow an understanding of crustal composition, volatile content, and evolution of terrestrial planets, yet the emplacement of ejecta deposits on bodies throughout the solar system is still debated. Here, we present the first detailed geomorphologic map of Bakhuysen Crater. We distinguish two distinct ejecta units: (1) a largely hummocky ejecta unit (Be1) that comprises the continuous ejecta blanket; and (2) an uppermost, discontinuous unit (Be2) with a distinct ponded morphology, pitted texture, and previously unreported lobate and flow deposits. Pitted materials are present in the crater interior deposits as well as the ejecta. Bakhuysen is the largest Martian crater thus far identified with crater-related pitted material, which has been suggested previously to represent volatile-rich primary impact melt-bearing deposits. Unit Bel is interpreted as the continuous ejecta blanket emplaced through ballistic sedimentation and radial flow. Unit Be2 shares many attributes with impact melt-rich ejecta seen on other planetary bodies (e.g., Earth, Moon, and Mercury) and is interpreted as having been emplaced as ground-hugging flows during the later modification stage of crater formation. Channels are observed as having emanated from Bakhuysen impactites and represents a clear example of the role of volatiles in the impact cratering process on Mars. Bakhuysen ejecta deposits and its associated features suggests that, if indeed a substantial volatile source is sampled by Martian impact events, then the formation of ejecta-associated channels on Mars are likely genetically linked to the formation of pitted materials where present. The preservation and exposure of the impact deposits of Bakhuysen present a unique opportunity to study these features and their relationship to the impact process on Mars.