Skip to main content
SearchLoginLogin or Signup

Characterization of the atmospheres and surfaces of the rocky exoplanets TRAPPIST-1c and LHS3844b with MIRI on JWST

Presentation #103.05 in the session Early Results from JWST - II.

Published onApr 03, 2024
Characterization of the atmospheres and surfaces of the rocky exoplanets TRAPPIST-1c and LHS3844b with MIRI on JWST

Rocky planets orbiting M-dwarf stars are among the most common planets known in the galaxy. While many of these worlds have similar densities to the Solar System terrestrial planets, they may have vastly different atmospheres and geology due to their short-period orbits. Here, I will present two recent results from JWST to characterize the atmospheres and surfaces of two rocky exoplanets: (1) We detected thermal emission from the dayside of TRAPPIST-1c with MIRI at 15 microns. The high dayside brightness disfavors a thick, CO2-rich atmosphere on the planet. A Venus-analogue atmosphere with sulfuric acid clouds is also disfavored at 2.6 σ confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO2-rich atmosphere on TRAPPIST-1c suggests a relatively volatile-poor formation history. If all planets in the system formed in the same way, this would indicate a limited reservoir of volatiles for the potentially habitable planets in the system. With our observations, TRAPPIST-1c is now the smallest rocky exoplanet with a measured flux. (2) Previous Spitzer observations of the hot planet LHS3844b indicate that it is most likely a bare rock, inviting detailed study of the surface. We recently used MIRI/LRS (5 - 12 microns) on JWST to observe three eclipses of the planet, leading to a confident detection of thermal emission coming from the planet. Our emission spectrum tightly constrains the surface fractions of different rocks, including basalt (expected from volcanism akin to present-day Earth), ultramafic rock (expected from a solidified magma ocean), and granite (an indicator of crustal reprocessing). Our data is also highly sensitive to trace amounts of sulfur dioxide that could arise from ongoing volcanic outgassing (100 ppm sulfur dioxide in a 0.01 bar atmosphere is detectable at over 3 σ confidence). These measurements provide the first empirical constraints on the geologic history of a rocky exoplanet orbiting an M-dwarf.

No comments here