"Some of the very largest secondaries, [typically those are usually about five percent of the diameter of the primary.]" -Kelsi Singer

This LPI is a study looking to infer what happened in the impact process. It's looking at secondary craters, craters made from the largest debris from the initial impact. So the size of debris should tell you something. What exactly?

• The slide at 3:20 really gives you a feel for how many craters can be secondary impacts, not direct foreign impacts. This can be really eye-opening. The smaller debris are more likely to make escape velocity than the larger ones.
• At 4:20, a high resolution close-up of diminutive secondary craters.
• Slide at 4:32 shows you the V-shaped features, implying debris was skipping! Or at least entering at a very low angle.
• Faint V-shaped secondary close-up at 5:00.

The remainder of the lecture is a whole lot of isolating simple variables to make estimation of ejecta more formulaic. This isn't difficult algebra, but it makes it plausible to do stuff like find an asteroid with a certain mass and velocity, and maybe scale back the path it took eons ago, to its initial crater. Albeit that wont apply to most asteroids, but that's sort of the upper-limit of what this kind of research can do.