Craters in the vicinity of Valles Marineris region, Mars: Chronological implications to the graben and pits activities

Abstract

Graben and pits are features closely associated with the Valles Marineris (VM) region on Mars. Earlier studies indicated that they are likely precursors for the VM trough formation, and thus they may assist in our understanding of how long the trough formation prevailed in the vicinity of VM. This study aims to understand how the graben and pit formation varied chronologically and spatially within a ~100 km vicinity of the VM region. We examined 1516 craters and found 48 craters that are superposed/cross-cut by graben, pits, and troughs or vice-versa with adequate ejecta or floor area for dating. Tithonium region graben and troughs cross-cut the craters around ~3.7 Ga. In the Ophir region, pits are formed on or post ~3.92 Ga at different elevations and have variable depths. Pital crater in the Ophir region interestingly hosts: 1) a broad catena ~14 km wide crosscutting its NE rim likely formed on or post to ~2.61 Ga, which inferred to be one-tenth to the adjoining Candor Chasma width of VM, 2) lobe like deposits associated with the catena emplaced over the Pital ejecta formed around ~1.14 Ga and 3) ~2 km wide pit superposed the lobe that reveals pit activity plausibly prolonged during Mid-Amazonian. Overall, our results likely point towards the contribution of graben and pits in the modification/development of peripheral areas of VM up to at least Mid-Amazonian. Thus, this study substantiated that the period and extent of graben and pit activities varied around the VM region.