MAPPING AND SIZE FREQUENCY DISTRIBUTION OF CORINTO CRATER SECONDARIES IN ELYSIUM PLANITIA ON MARS

Corinto crater is a 13.9 km diameter fresh rayed impact crater in Elysium Planitia on Mars. The crater is elliptical and has asymmetric, lobate ejecta suggesting an oblique impact from the northeast. Corinto secondaries cover young lavas and are older than Zunil secondaries indicating it formed between 0.1-1 Ma and 2.8±0.5 Ma. Distinct dark elongate rays in nighttime THEMIS images are observed radial to and dominate the region out to ~1400 km south of Corinto. They contain dense clusters of secondary craters with distinctive light-toned ejecta. The rays were mapped and classified into three facies based on thermal characteristics and crater counts were performed in facies two and three.

Facies one rays extend from the Corinto ejecta blanket to ~120 km to the south and ~60 km to the north They are up to 5 km wide and exhibit dense secondary craters at the CTX scale but are not distinct in thermal images. Facies two rays are lobes, up to 50 km wide and 100-300 km long that extend south of Corinto from ~125 km up to ~310 km. This facies is resolved in CTX with some crater diameters exceeding 350 m. The third facies of rays are darkest in nighttime THEMIS indicating that they have the lowest thermal inertia. These rays extend radially south from ~300 km to as far as ~1400 km.

The size frequency distribution of Corinto secondary craters within facies 2 and 3 were counted based on HiRISE coverage. The cumulative size frequency distribution for craters >15 m for facies two and three follows a power law slope near -4, which is a steeper slope than crater production functions that purportedly include primary craters and far-field random secondaries. The average slope over all thermally distinct rays for Corinto is similar to Zunil crater rays, (~-4.9 for craters >15 m diameter). Counts of all facies 2 secondary craters with diameters >5 m have a power law slope of ~−3 while facies 3 have a slope of ~−4. These distributions exhibit a slight rollover at the lower diameter bins but the slopes are still greater than the Mars crater production functions described above. The cumulative frequency of craters at each diameter bin is lower for facies 3 relative to facies 2 at >5 m and >15 m diameters.