Interview with Sarah Hörst: Planet Doctor and Titan Evangelist
published during a waxing gibbous moon.

Sarah Hörst

The illustrious Dr. Sarah Hörst. Credit: Sarah Hörst

Dr. Sarah Hörst is one busy scientist. Her first lab is up and running at Johns Hopkins University (which you can follow here), she’s a member of the Science Definition Team for NASA’s potential Europa lander, and she’s working on a mission proposal called DAVINCI, which plans to head back to Venus. Planetary Science is her specialty, specifically planetary hazes on Titan, Europa, and Pluto. Of these, she’s most interested in tholins, which are chemically complex and gunky organic solids left behind from energetic chemical processes. She wrote a detailed blog post explaining tholin (as opposed to tholins, but more about that below) in a way that even we could understand over at The Planetary Society.

In addition to all the cool science she does, Dr. Hörst also teaches, frequently shoots off hilarious tweets, and passionately advocates for getting more women and minorities into STEM fields. Given all this, we’re both amazed and grateful that she managed to find the time to speak to NOW.SPACE writer, Shannon Stirone. Thanks, Dr. Hörst!

SS: When did you first know you wanted to become a scientist?

SH: I’ve loved science for as long as I can remember, but I can’t really point to a moment or even an age when I decided I wanted to become a scientist. I think I’ve always been interested in so many things and in so many different possible paths (I have a literature degree too, for example) that I could’ve ended up going down a number of different paths. It just so happens that all of the decisions that I made brought me down this path.

“Do all the good you can, by all the means you can, in all the ways you can, as long as you ever can”

SS: Who were your role models growing up?

SH: My dad was a doctor, and my mom is a scientist. My mom went to grad school when I was in elementary school, and she got her Ph.D. (in neuropharmacology) when I was in middle school, so I watched my mom go through the experience of getting a Ph.D. I actually helped her put together the bibliography for her dissertation. My mom and dad both worked really hard at jobs that they enjoyed and excelled at, and they always talked to me about their work and encouraged me to be curious and seek answers. Even now I have other mentors and people that I guess I consider to be role models in terms of the kind of planetary scientist I would like to be, but in terms of the kind of person I aspire to be, I never needed any other role models besides my mom and dad.

My dad passed away unexpectedly last fall, and I’m still trying to figure out how to be a scientist without him. My dad’s best friend described him as the embodiment of the saying “Do all the good you can, by all the means you can, in all the ways you can, as long as you ever can” and I think that is actually a perfect description of both of my parents and something that I have very much internalized as the way to approach any task in life.

SS: You recently got your first Dr. Sarah Horst laboratory at Johns Hopkins, what was that experience like for you?

SH: It is still kind of weird honestly. I’m just now (almost two years later) getting to the point where I can walk into my amazing office or lab and not be a bit startled that it is mine. Trying to get a lab up and running while trying to unpack from moving, starting teaching, trying to get a research group going, etc. can be pretty overwhelming. I remember walking into my lab when they finished the renovations and looking around at this beautiful new space and realizing that it was completely empty. There were tables and cabinets and fume hoods, but there was literally nothing, and I just thought, “Wow, we have so much to do.”

Starting from scratch is a wonderful opportunity, but it can be kind of terrifying sometimes. Our first research group outing was to Home Depot. We ended up with two completely full shopping carts of basically anything you can imagine: wrenches, zip ties, wire strippers, safety goggles, step stools, brooms, etc. It has been really gratifying over the past year watching my lab go from this new, empty space into this kind of organized science chaos because it means that we are finally doing science.

SS: What do you think about more, Titan or Europa?

SH: I spend most of my time thinking about Titan, although for the past few years there have been many more opportunities to think about Europa and work towards future exploration of Europa, which is really exciting. We still have a lot of work to do on Titan, and that’s usually the world where you’ll find both my mind and heart.

SS: What is the most interesting thing about Titan in your opinion?

SH: I don’t think I can even answer that question because honestly, my first thought was, What isn’t interesting about Titan?” In the end, I guess many of the really interesting things about Titan fall into one category–which is that in many ways, Titan is very similar to Earth (thick nitrogen atmosphere, clouds, rain, rivers, seas, dunes, etc.) and yet, at the same time, it is a drastically different temperature, completely different materials, etc. This is one of the reasons why Titan is so wonderful and important to study because it allows us to test a lot of ideas about how planetary processes work by giving us a test case that has very different conditions than Earth.

Sarah Hörst

Titan’s haze. Credit: NASA / JPL-Caltech / SSI

SS: How exactly can you study planetary atmospheres like Titan and Europa in a lab? What sort of tools do you use to create these analogs?

SH: There are a couple of different ways to do this in the lab. We simulate the chemistry that occurs in planetary atmospheres by building a chamber that contains the gases of a specific atmosphere (nitrogen, methane, and carbon monoxide, for example, to study Titan) and then we expose those gases to some kind of energy source that breaks up the original molecules and starts chemical reactions. We usually try to understand how those gasses get converted into particles like the ones we see in the atmospheres of Titan and Pluto, and once we make particles, we can learn other things about them like how they interact with light or what they are made out of.

Sarah Hörst

Titan. Credit: NASA/JPL-Caltech/SSI/Kevin M. Gill

SS: Tell me about tholins. They are all over the solar system, what could this mean for finding life, or evidence of past life?

SH: I tend to prefer to use the word tholin only to refer to material that is made in the lab to prevent confusion but I think I’m fighting a losing battle there. Whether it is found in the lab, or elsewhere in the solar system, tholin refers to complex organic material produced by exposing cosmically abundant gases and solids (like nitrogen, methane, carbon monoxide, etc) to an energy source (photons, electrons, ions). The energy breaks up the small molecules initiating chemistry that results in the formation of a solid composed of much larger molecules (and a large number of different molecules).

Depending on your definition, this material is present on comets and asteroids, Kuiper Belt objects (like Pluto), Jupiter, Saturn, Titan, Triton, etc. We still don’t know very much about if–and how–this material could contribute to the origin of life. One thing we do know for sure, though, is that we need to be able to tell the difference between complex organic material like this (that does not originate from life), and complex organic material that is the signature of extant or extinct life–so that if we do find an organic signature of life elsewhere in the solar system, we can recognize it.

Sarah Hörst

Formation of tholin. Credit: Sarah Hörst

SS: Where’s the weirdest place we’ve found tholins so far?

SH: I don’t think they’ve necessarily shown up anywhere we didn’t expect them. It may have been a bit surprising for people when Pluto turned out to be so hazy with large red (presumably organic) deposits on the surface, but there had been evidence for years that Pluto had a haze layer and I think many of us who study this type of chemistry expected Pluto to be hazy before the New Horizons encounter.

I will admit that although I was on the record that Pluto would be hazy, I was still surprised that it was visible in the imaging data. In my head, the particles would be small enough and/or sparse enough that it would require analysis of data from the ultraviolet instrument to detect the haze and that the evidence would on a normal (kinda boring) scientific plot. I am so happy that it is visible in the imaging data, both because the images are absolutely stunning and because having an actual picture is really powerful from an education and outreach perspective.

SS: We are scheduled to launch to Europa in 2022, what data are you most excited about getting back?

SH: Overall, I’m most excited for the collection of data that will be returned, because each set of data is just one piece of the puzzle and a spacecraft like the one we will send to Europa is most powerful scientifically when all of those pieces are assembled into a bigger-picture understanding of the world. I guess generally my two favorite types of data are imaging data, which I think causes this really emotional reaction for people in addition to being incredibly scientifically valuable.

Sarah Hörst

Pluto’s haze layer shows its blue colour in this picture taken by the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC). Credit: NASA/JHUAPL/SwRI

When I saw the first image of Pluto’s haze, I actually cried. I am really excited about the data from the mass spectrometer, which will measure the composition of Europa’s atmosphere directly by sampling it. Mass spectrometry is an incredibly powerful tool and it will play a huge role in answering many of the questions we have about Europa. I’m not actually on any of the Europa instrument teams, but just like with the New Horizons Pluto encounter, I will be super excited to watch the mission unfold as a very interested and invested outsider.

“Science is becoming more diverse–painfully slowly”

SS: What are your current thoughts on women in science? Particularly those in astronomy or planetary sciences?

SH: Over the very long term, science is becoming more diverse–painfully slowly. An example from my own life is that my mom could not have gone to college at Caltech like I did, because when she went to college Caltech didn’t admit women. So we’re only one generation removed from one of the world’s most prestigious science and engineering schools actively excluding more than half of the world’s population.

In some ways, then, we have made a lot of progress, but the academy is rife with sexism (overt and otherwise) and it is going to take a lot of effort on the part of a lot of people to fix it. We have other serious problems that must be addressed as well that aren’t talked about nearly often enough, if at all. Although Caltech, for example, has made progress in admitting women, the percentage of undergraduates at Caltech that are black, Hispanic, and/or Native American does not even remotely reflect the population of the US today. Systemic racism, ableism, discrimination based on gender identity and sexual orientation, and other forms of discrimination all prevent extremely talented and creative people from being able to pursue STEM careers and those that do suffer from microaggressions and outright discrimination. We have to do better.

SS: What advice would you give to women or anyone wanting to get into a STEM field?

SH: This advice isn’t just for girls and women, but for anyone who is interested in STEM. Many people will act as if there is only one way to be successful in a STEM career and that there is only one path to that point. They are wrong. There are many different paths, there are many different successful outcomes. For a really excellent example see this website , which profiles numerous women in planetary science.

The people who act as if there is only one way to be successful play a large role in the problems that we have with diversity and inclusion in STEM and those problems become self-reinforcing. If someone tells you that you can’t do what you want to do because of who you are or want to be or what you need to be successful, that person does not have your best interests in mind and they are failing at their job. You do not have to listen to them. Ask someone else for help. If you don’t know who to ask, ask me and I will find someone if I can’t help you myself.

Creative problem solving is basically the job description of a scientist, so if someone tells you something isn’t possible or cannot be done then they are not only failing at being a teacher, advisor, or mentor but also a scientist. The people who have been most important in my career are the people who have been willing to brainstorm solutions with me. It is important that solutions are plural because there is almost always more than one way to solve a problem and the way that works for one person may not work for someone else for a variety of reasons.

I have been lucky to find mentors who understand that the way that they would handle a situation wouldn’t necessarily work for me and they’ve helped me find another path forward. I wish someone had told me much earlier in my career that I didn’t need to be anyone other than myself to do science and I wish that I had understood sooner that I am the best scientist that I can be when I am doing all of the things that make me happy and whole, especially the things that are not science.

SS: What are you doing when you’re not working?

SH: I like to be active, especially outside, so I like to run, bike, hike, and ski. Since moving to Baltimore, I’ve also been working on the house that I bought when I have time, which is fun because I’ve learned how to do a lot of new things like install a tile backsplash.

One of the great things about working in a lab is you get really used to taking things apart and putting them back together and I find I notice that skill most when working on my house- I’ve taken apart the electronics in a million dollar instrument before so I can probably install a light fixture. I also like to craft (knit, crochet, quilt), garden, read, and watch home improvement shows.

SS: Who are the Booplefloofs and what, if any, contributions have they made to your successful career?

SH: The Booplefloofs are my two Pomeranians, Ewok (age 12) and Peanut (age 14). I got them both when I was in college, so they’ve seen me through undergrad, Ph.D., postdoc and now into a faculty position.

They aren’t particularly good at the computer, and they can’t do lab work because they have so much fur, but they’ve been a never-ending source of unconditional love and snuggles since I was in college, so they’ve certainly had a big positive impact on my career.