"I haven't really answered any questions yet." -Michelle Kirchoff

This is a really fun LPI. It involves comparing images of craters with focus on Mars' presumed wet splat-type rampart-craters.

Here's the thing, the law of superposition works well with crater ejecta. However you can't really interpret more than a few layers of overlapping ejecta. It works best on places like Callisto and Ganymede but also applies to Luna, Mercury, and Mars.

Mars in particular gets weird because it has a lot of Rampart-craters. You can employ the law of superposition in the Noachian south, but not so much around the Hesperian equator. So how do you infer some relative dating?

• Slide at 2:60 shows a random distribution for both Ballistic-craters and Rampart-craters on Mars.
• From 10:00 on she's showing older images compared with newer images of the same craters to demonstrate how the interpretation of ejecta type has changed. 

One would think you could just say that Rampart-craters are older than Ballistic-craters, but that doesn't seem to work. Frequently craters have traits of both types. It's entirely possible that all Rampart-craters were hybridized at first. Wind erosion seems to have dulled or removed a lot of radial ejecta.

In the end this LPI is the type that brings into question things one would have thought fairly straight forward. Which is neat. Now one can say that currently, in the case of Mars, dating craters is a bit more complicated. And this further throws into question the chemistry/mechanical-action that causes Rampart-crater morphology.