CosmoQuest has a large presence at this year’s AGU in Washington, DC, from Dec 10-14, 2018. We have a number of posters and presentations by our team members. If you’re there, come by and check out what we’ve been doing!

Stuart J Robbins of the Southwest Research Institute Boulder will be presenting the poster P23F-3505: Investigating Mercury’s Large Crater Stratigraphy and Kilometer-Scale Primary and Secondary Crater Populations

When: Tuesday, 11 December 2018 13:40 – 18:00
Where: Walter E Washington Convention Center – Hall A-C (Poster Hall)

Description: We will present a report on a detailed investigation into Mercury’s large-crater stratigraphy and implications on the reliability of using smaller (~km-scale) impact craters for relative and absolute model age calculations. Our work has two primary components.
First, Mercury’s larger (>~50–100 km) impact craters can be put into a relative framework based on the stratigraphic relationships between the craters. These relationships are determined by which crater cavities themselves are superposed on other craters, crater ejecta, distinct secondary crater chains, and/or crater rays.

Second, the role of secondary impact craters in contaminating crater counts on Mercury is investigated. Since MESSENGER observations began, researchers have investigated this issue and identified secondary impacts can dominate crater populations as large as10 km, which would be larger than on any other observed solar system body. However, some research suggests that is not the case, and/or that secondary craters can be reasonably separated from primary craters. If so, ~km-scale impacts can still be useful for relative and absolute model ages. We are testing this idea by identifying superposed small craters on the larger craters used in our stratigraphic framework. The stratigraphy must be correct – e.g., a crater overprinted on another cannot be older than the crater it overprints. Therefore, the stratigraphic framework will provide a “ground truth” we can use against which to test the relative ages of the crater floors based on the superposed crater counts.

We will report on: Progress testing the superposed craters against the stratigraphy, whether the superposed craters support or are in conflict with the stratigraphy, and whether any conflicts can be mitigated by using traditional methods of removing secondary impact craters (e.g., craters in chains or tight clusters). Data for the superposed craters comes in part from the CosmoQuest citizen science portal, which allows volunteers from around the world to help scientists by identifying features on bodies across the solar system.