Keavin Moore, a PhD student at iREx, recently completed his PhD at McGill University. Here he summarizes his doctoral research project.
Life as we know it – organic life on Earth – relies on having liquid water around. Even though we orbit a “yellow” star, the Sun, most stars in the universe are smaller and less bright red dwarf stars. These smaller stars offer a bunch of planets that could potentially support life. We hope to study and understand them better in the near future.
However, red dwarfs are more active, and the radiation and particles they emit puts the planets orbiting them at risk of losing their atmosphere. During my Ph.D., I created a model that combines what we know from astronomy, atmospheric science, and geophysics to study rocky planets around red dwarf stars and explore the water content – and thus potential habitability – of these abundant worlds.
My first project looked at how water moves between the inside and surface of an Earth-sized planet, driven by things like plate tectonics. The model showed that water could be stored in the planet’s mantle (i.e., the middle layer of a rocky, terrestrial planet, between core and surface), protecting it from being lost into space. This could eventually lead to a stable liquid surface ocean. We then improved the model to make it more generalized and complex.
The next version of the model considered the earliest stage of a planet’s evolution when it’s extremely hot. At this point, there’s a molten silicate (rock) ocean that goes from the planet’s surface to its core, where water is soluble. This ocean acts as a shield, preventing water from escaping into space. Our simulations suggested that this long-lasting reservoir could significantly improve the chances of habitability for planets around red dwarf stars.
Finally, I collaborated with two undergraduate students on their senior theses to study how a planet’s mass affects its habitability. Larger planets are better at holding onto water, but sometimes a lot of it gets trapped in the planet’s mantle, which doesn’t help with surface habitability.
Our simulations provide a solid foundation for further research on the habitability of rocky planets around red dwarf stars and stress the importance of studying planets as complete systems.
Keavin completed his PhD at the McGill between 2018 and 2023, under the supervision of Professor Nicolas Cowan of iREx. His thesis will be available soon.