Habitability and Biosignatures of High-Obliquity and High-Eccentricity Exoplanets
September 6, 2023. 4:15-5:15 PM, 2400 Atlantic Building
Taken by Dr. Merck outside lecture hall with Rahul,
another SGC Student. I am on the right.
As a first semester freshman, I attended an astronomy colloquium given by Dr. Stephanie Olson of Purdue University and organized by Dr. Leslie Sage of the University of Maryland. The title of the talk was "Habitability and Biosignatures of High-Obliquity and High-Eccentricity Exoplanets." This talk was one of many astronomy colloquiums being organized by UMD over the semester, and this talk took place on Wednesday, September 20, 2023. The talk was from 4:05 to 5:00 PM in one of the Atlantic Building's auditoriums.
During this talk, Dr. Olson attempted to explain what in her view would be the optimal conditions for a planet like Earth to exist outside our solar system. She argued that such a planet would have to be in a "habitable zone," but also claimed that some of the planet's own characteristics determine its ability to support life. She focused on obliquity(tilt of the planet's axis) and eccentricity(deviation from circular orbit) as being important in creating the necessary conditions needed for habitability. Using data simulations with the continents of this proposed planet being in the same locations as the continents on Earth, she came up with a few conclusions on the effects of obliquity and eccentricity. She concluded that high obliquity would cause more dramatic seasons, and that medium to medium high obliquity would increase vegetation on land. She added that medium eccentricity would cause an optimal amount of vegetation. However, she noted that very high obliquity would cause land to become very arid, inhibiting vegetation on land. However, High obliquity would provide the desirable conditions for life to thrive in the oceans. Dr. Olson theorized that seasonal cycles could be required on a given planet for life to begin, and her conclusion was that a world with high obliquity and high eccentricity may be superhabitable.
Overall, the talk was conducted at a very high level, and I believe that the intended audience was definitely for graduate students and other academic professionals. With that being said, there were some things that I could take away from the discussion. I agree that her conclusions regarding obliquity and eccentricity are definitely correct for planets where continents are placed in locations similar to that of Earth, as the programming simulations she and her team used made that assumption. However, as Dr. Merck pointed out to me after the conference, Dr. Olson did not account for the situation that the continents and the oceans of the planet would be in different locations. Obviously, if the continents were located in different spots, the effects of obliquity and eccentricity could in fact be very different from the conclusions Dr. Olson described. Nevertheless, with my limited knowledge of the subjects being discussed, I found myself being easily convinced by Dr. Olson's conclusions(after all, she is a PHD and I am an undergrad who doesn't even study astronomy). I didn't find any logical fallacies in her talk, and she was good at providing meaningful definitions so that viewers of all ranges of background knowledge would be able to follow and understand the discussion. I have always been aware of a "habitable zone" where a planet would have to be located to sustain life, so I agree with her premise of assuming that any planet that could sustain life must be in the habitable zone. My knowledge of obliquity and eccentricity comes from AOSC 200, which I am taking this semester, and it is clear to me that obliquity especially plays a major role in causing the seasons on our planet. Dr. Olson concluded from her models that seasonal cycles would be necessary for an exoplanet to be superhabitable, and thus an exoplanet having a high obliquity would make quite a bit of sense to me. Dr. Olson was also good in explaining that simply the presence of a gas like oxygen or CO2 would not mean the existence of life, and that many other factors would need to be present for a planet to be superhabitable, so I would say that the speaker was careful in not rushing to judgements and making bold claims that might not necessarily be true. The speaker also noted that a high eccentricity would lead to more global seasons, which based on my knowledge of eccentricity from AOSC 200, seems to make sense. Overall, I will say that Dr. Olson could have programmed her simulations to test for when continents were located in different locations, but her conclusions did not contain logical fallacies and were thorough otherwise from my understanding.