Comparing Exoplanets to Planets in Our Solar System with Dr. Jim Kasting


SpaceBites talks with Dr. Jim Kasting, an Evan Pugh Professor of Geosciences at Penn State University, about what we can learn about our Solar System by studying the structure of other solar systems and their exoplanets. Kasting is a world leader in the field of planetary habitability, assessing habitable zones around stars, and is a Project Blue Earth Scientist, along with Dr. Colin Goldblatt.

SpaceBites: Dr. Kasting, can you tell us a little about yourself?

Dr. Kasting: Hi, I’m Dr. Jim Kasting, I teach geoscience and planetary science courses at Penn State University. My primary specialty and research focus is in atmospheric evolution, planetary atmospheres, and paleoclimates. My writings are about the geophysical history and status of the Earth, with a focus on atmospherics.

SpaceBites: What was the path you took to lead you to this research?

Dr. Kasting: I worked as a postdoctoral fellow at the National Center for Atmospheric Research and at NASA Ames Research Center before accepting a position with the space science division at NASA Ames. During my tenure at NASA, I served in various capacities, which broadened my scientific interests. Later, I worked as a member of the scientific working group for the Terrestrial Planet Finder, a large 8-meter-class space telescope mission concept to detect and characterize Earth-like planets around other stars. In 1988, I joined Penn State University and have been there since, however, I continue to collaborate with NASA and remain active in NASA’s search for habitable extrasolar planets.

SpaceBites: What have you learned about exoplanetary systems around other stars that is different from our own Solar System?

Dr. Kasting: The biggest thing is that planets in some systems do a lot of radial migration, that is, they may form in a particular orbit but migrate to different orbits because of gravitational interactions with other bodies through time. This could have been important in our Solar System, as well. But at least in our system, the rocky planets are on the inside and the gas giants are on the outside. This is not always true elsewhere.

SpaceBites: What are the implications for habitable exoplanets with such a wide range of possible planetary systems?

Dr. Kasting: Eta_Earth (or 𝜼Earth), the frequency of Earth-size planets in the habitable zones of stars similar to the Sun, is about 0.1, or larger if you consider a wide range of rocky planet sizes. We know that now from the Kepler mission. That’s the same number that we guessed 20 years ago, but now we can justify it. Hopefully, we can use that information to help get funding for a big direct-imaging mission like the ones NASA is currently studying.

SpaceBites: To that end, you’re a member of numerous professional scientific societies and committees, including the BoldlyGo-led initiative Project Blue. What excites you about being part of this effort?

Dr. Kasting: I’m excited about any project that has the potential to identify terrestrial-type planets in the habitable zones of other stars. Project Blue’s focus on Alpha Centauri is interesting because it has two stars similar to the Sun where we can look with a small space telescope about the size of a common backyard telescope. Eventually we’d like to get full spectra of rocky planets within the habitable zones of nearby stars to see if they show properties like Earth, with oceans and an atmosphere that could potentially sustain life as we know it.

SpaceBites: When you are not thinking about habitable extrasolar planets, what else do you like to do?

Dr. Kasting: I swim, bike, work out, and play some racquetball and tennis. And I enjoy playing with my four grandchildren.

SpaceBites: Thank you for taking the time to speak with us today Dr. Kasting.

Dr. Kasting: My pleasure.

Dylan Horn