Ben Boatwright is a senior double majoring in geology and music. His geology thesis focuses on Martian terrestrial valley networks. His thesis advisors are Mt. Holyoke’s Visiting Assitant Professor of Astronomy Caleb Fassett and Amherst College Geology and Environmental Studies Professor Anna Martini.
Q: What is your thesis about?
A: I have been using a computer model called MARSSIM to simulate the erosion of valley networks on Mars. I have been trying to figure out why Martian and terrestrial valleys have different morphologies, such as various dimensional properties, by simulating changes in discharge (amount of water flowing per unit time) and impact cratering.
Q: Why did you choose this topic?
A: I only declared a geology major last academic year — originally, I was just a music major. I talked to Professor Tekla Harms about writing a thesis and told her I was interested in pursuing a planetary science thesis. She then directed me to talk to someone at Mt. Holyoke and got in contact with my eventual advisor, Caleb Fassett, who is [Mt. Holyoke’s] Visiting Assistant Professor of Astronomy and also the Five College Fellow of Astronomy. I first talked to him back in May of my junior year. He explained to me that he had a project on Mars and asked if I would be interested in that. I did not necessarily choose a topic myself, but I was very fascinated because I wanted to write about anything planetary science related.
Q: Could you explain the computer model you used?
A: This computer model is written in Fortran, which is an extremely early and fundamental computer programming language. Alan Howard from University of Virginia came up with this twenty years ago. Howard wrote this code that somehow mathematically models different physical processes. Everything is based on basic physical principles. On the user end, there is a parameter file that I can open using Terminal on Mac. Everything is in a text file and the user goes through a big list of variables that could be changed. For example, you can control the amount of discharge to model certain scenarios. I could also observe impact cratering through this computer model and alter sizes of craters, for instance.
Q: What was the research process like?
A: In the past, scientists have measured scaling laws of fluvial features where they looked at ratios of different dimensional properties, such as widths and lengths of streams. Something I specifically looked into was Hack’s law, which denotes the relationship between length of streams and the area of their watershed. If rain were to fall onto the surrounding area, the water within the watershed would be the part that would flow into the stream. This is really defined by the particular topography. There have been a lot of studies in the past ten to fifteen years that have found that watersheds on Mars are smaller than those on Earth for a given stream length.
Hack’s Law is a power function, where stream length is equal to the watershed area proportionally raised to some exponent. You can use this exponent (Hack’s exponent) to describe the relationship between to the two variables. High Hack’s exponent is more characteristic of Mars, where there was low discharge, while a lower Hack’s exponent is more characteristic of Earth. During our data collection, we would change the level of discharge. As the discharge increased, the Hack’s exponent would decrease, meaning the watersheds grew wider.
The other thing we did was impact cratering. The valleys we are looking at have been aged to 3.7 billion years old. Earlier in the history of the solar system, there were a lot more debris floating around. The rate at which the craters were impacting surfaces was much higher. We were investigating whether these impact cratering rates affected how the Mars surface was formed. Erosion on Earth happens so fast that it erases craters that form on the surface.
What we found is that despite the cratering rates being higher at the time, it is very unlikely that there would have been any impacts at all. When we simulated impacts at a very high rate (one every ten years, for instance), valleys didn’t have enough time to form. All of this relates back to how the valleys formed in the first place on Mars, where it is very dry and cold. Was there a climate three billion years ago that could have supported liquid water on the surface? The big argument has been frozen water could have melted, but the other side of the discussion is that it had to be water flowing over the surface, which requires a warmer climate. Our simulation was run on the basis that it was flowing water over the surface, which is tied in to the latter argument of the debate.
Q: Has there been extensive research on your topic in the past?
A: What we are specifically doing is fairly novel, but studies started once technology was advanced enough to take global satellite images of Mars. That has been feasible since the late 70s. There was the Mars Global Surveyor that was launched in 1996, which was able to produce high-resolution images of the surface of Mars. That is the best satellite image data available now on a global scale.
Q: What has been the general timeline for your thesis?
A: While everyone was proposing his or her topics to advisors, I didn’t really have to. Rather, the proposal was a declaration of what I was going to do with the project Professor Fassett introduced to me. Starting this academic year, I traveled to Mt. Holyoke once a week to meet with Fassett for a few hours at a time. I really liked the topic, so I never minded the commute.
Over the summer, I did background reading. Once the semester started, we started right away with the basic configurations with the computer part. Simultaneously, I was doing the background reading. I definitely needed to wait to write the methods section until I knew for sure what was going on, so I waited to do that until Winter Break. Spring semester was spent on collecting the data that we were going to use. Generally, it was mostly writing in the fall and data collection in the spring, but I had to do both at the same to a certain extent.
I turned in the final draft that I will be graded on last Wednesday. The geology Faculty will go through my paper and recommend changes. After that, I will make my final corrections and turn that into the department and the registrar. I could potentially continue the research because it doesn’t seem like there is a designated endpoint.
Q: What has been some of the difficult things about writing a thesis?
A: I spent the whole fall semester trying to debug the computer model because there are so many things you can do right or wrong. Professor Fassett and I spent a lot of time playing around with the model in order to have it give the outputs we wanted and were accurate. Sometimes, you could change just one number and the result would be completely different. It would be extremely frustrating when I could not find an explanation to justify why something had happened.
Q: Do you think you will be taking away valuable lessons from thesis writing that you can apply to your graduate school education?
A: This hydrology-related topic is not necessarily the field that I am interested in, but having completed an extensive research process will definitely help me in graduate school. The specific topic of my thesis is something I want to continue on my own, but in graduate school, I am more interested in the surfaces of outer planet moons. But my topic and my interest are still interlinked — for instance, Titan, the largest moon of Saturn, has an atmosphere that is made of mostly hydrocarbons. Based on the radar reflectivity, scientists have observed that there are lakes and basins on Titan. My thesis on hydrology on Mars could definitely be applied to that. Everything is all related.
Q: Do you have any advice for future thesis writers?
A: It is good to plan ahead. I did and I got a lot done well in advance, but even then, I spent the last three days before the due date staying up until five in the morning. Also, collaboration is key. It is important to be self-sufficient, but you also have to be able to talk to your advisors and take what they have to offer. Along that line, it was very beneficial to utilize resources within the Five College Consortium. Having a primary advisor who is not an Amherst faculty was feasible and I got to make the best of my resources through a Mt. Holyoke professor.
