Presentation #407.01 in the session Atmospheres 3.
The study of rocky, terrestrial exoplanets and their atmospheres has attracted increased interest in recent years, focusing especially on small planets orbiting M dwarfs whose properties can best be studied with existing observatories. In particular, the bulk (mineral) content of these planets and the extent to which they can retain their atmospheres in the face of stellar activity both remain open questions. The most likely route to addressing these questions relies on measurements of these planets’ intrinsic thermal emission spectra, but such measurements have so far been made for only one rocky planet, LHS 3844b.
Here, we will report on our successful measurement of the infrared thermal emission from a terrestrial planet, just the second such measurement made to date. At 1.2 Earth radii our target is smaller than LHS 3844b; both planets orbit M dwarfs, but (unlike LHS 3844b) the mass of our target is known from radial velocity observations. Our measurement begins to constrain surface mineralogy and also reveals that the planet has essentially no atmosphere for a wide range of plausible atmospheric compositions. This result hints at an emerging trend: that small, rocky planets orbiting M dwarfs may have difficulty keeping their atmospheres over Gyr timescales.