One of the key determining factors for exoplanet habitability is the condition of its atmosphere. It then becomes important to understand the mass loss mechanisms that might affect exoplanets after their formation and through their evolution. This work will be to develop models of this mechanism. The team will adapt an existing model to three similar transiting planets which orbit similar stars. Two of the three planets show evidence of atmospheric evaporation in their transits, but the third planet does not. These three worlds, so similar but yet with such different results for atmospheric evaporation, might provide a unique insight into planetary evolution. This work will support a graduate student and will support four female undergraduate interns. Part of the internships will include participation in a workshop on science communication. The PI will also conduct outreach by participating in the Dartmouth Foreign Studies Program in South Africa.
The team will adapt the Evaporating Exoplanet code (EVE) by including three new phenomena that have not yet been incorporated into the code. They will use the code to produce models of three similar exoplanets around three similar stars: K2-25b, Gl 436b, and GJ 3470b. Of these, K2-25b has not been observed to exhibit atmospheric evaporation, but the other two have. Once these systems have been understood, the team will conduct a parameter study to assess how planetary exospheres are impacted by their stars across a range of stellar and planetary parameters. In particular, the team will explore the efficacy of particle-based models versus hydrodynamic codes for the full 3D stellar wind problem. They will also include pickup protons which result from charge exchange between the planetary exosphere and the stellar wind. Prior models neglected this potential source of particles. They will also explicitly model atmospheric helium, which has not been included in prior models.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
