Mika Huffman

Broadly, I study impact events- the impactors that cause them and the targets they hit.

I studied the carbon dioxide content of comet 45P/Honda-Mrkos-Pajdušáková using observations of the forbidden oxygen transitions. I published a paper in the Planetary Science Journal on this work. Comets are important to study because they are frozen "fossils" of the early Solar System's composition. If we learn what comets are made of, we can determine what the forming Solar System was like. Carbon dioxide is an important component of comets. But, it's difficult for us to study carbon dioxide content from telescopes on Earth, since the light given off by CO2 transitions is absorbed/blocked by our atmosphere. We used a workaround- studying oxygen transitions from broken-apart CO2- to figure out the carbon dioxide content of 45P/HMP.

My second project was looking at how impact events affect planetary atmospheres. If you drop an ice cube in a glass of water, you'll end up with more than when you started. But, you can imagine hurling a snowball in really hard, and splashing out more water, leading to net loss. Comets and asteroids have ice in them that can turn to gases when they hit a planet. So, a small, slow comet could net add atmosphere, while a big, fast asteroid may net remove. I looked at the net effects of many impacts over a long period of time. Would a bombardment period lead to net atmospheric gain or loss for Venus, Earth, and Mars? If they tend to net add, then impacts could rehydrate previously dessicated exoplanets. If they net remove, we may be overestimating the number of habitable worlds out there. I compared a bunch of different existing models in the literature, and found that they differ by several orders of magnitude. We don't know if a bunch of impacts would net add or net remove atmosphere! I published a paper in JGR: Planets on this work.

For my current/upcoming research, I'm going to improve upon those disagreeing models by making my own, using a shock physics (rocks hitting other rocks really hard) hydrocode (treats everything like a liquid) model on CU's supercomputers. We've tried iSALE, but think that CTH (a US government munitions code) would be better. We're working on getting access to CTH right now. For the final arc of my research, I plan to expand these results to exoplanets.

For my third project, I discovered tertiary craters on our Moon. When an impact occurs, it creates a primary crater. But, during that formation process, the impactor throws out a bunch of ejected material, which can in turn create their own smaller, secondary craters. I wanted to know if there were secondary craters of secondary craters- tertiary craters. I am the first person to discover these craters. Normally, primary and secondary craters are really fast, big, and high energy. The rock that makes the crater is gone- vaporized, melted, fractured, or buried. But, since tertiary craters are slow, small, and low energy, we can see the actual boulder that made the crater downrange, on the surface. We can use some scaling laws to determine the size of the rock that would be needed to make the tertiary crater, then compare that prediction to the actual size of the boulder on the surface. They match! We use the tertiary craters as an observational check on the scaling relations that we've developed here on Earth. A paper on this project is currently in preparation.