DETAILED ORBITAL MAPPING HIGHLIGHTS RELATIONSHIPS AMONG JEZERO CRATER FLOOR UNITS
Here we explore map-scale relationships between geologic units that are exposed at the crater floor. These units include: Crater floor fractured rough (Cf-fr), which is a regional, roughly planar, crater-retaining unit with lobate margins; and two morphologically distinct units (lower and upper Séítah) that lie outside of the lobate margins. In a new orbital mapping effort, we further characterize relationships between these units. First, we identify that the basal 2-6 meters of Cf-fr contain discrete layers that are exposed either inside or outside of the lobate margin, depending on topographic relief of the substrate. Séítah rocks consist of two distinct regional units, including a lower, polygonally fractured unit with strong spectral signatures of olivine in CRISM, and a spectrally distinct, higher-standing pinnacled unit.
Layering within the basal Cf-fr permits Cf-fr to be distinguished from laterally exposed Séítah rocks and shows the Cf-fr to overlie Séítah. Layering within Cf-fr also changes in overall thickness and in the number of observed layers along the lobate margin, indicating that layered strata were likely deposited over pre-existing topographic relief associated with an erosional unconformity between the units. Higher-standing portions of the upper Séítah also occur at a variety of topographic positions with respect to polygonally fractured lower Séítah, suggesting the potential for an unconformable relationship between upper and lower Séítah units. Together, these relationships suggest a complex geologic history within Jezero crater characterized by periods of deposition separated by periods of erosion.