James Webb Space Telescope Feed Post

Webb Rules Out Thick Carbon Dioxide Atmosphere for Rocky Exoplanet (Spectrum)

TRAPPIST-1 b lacked atmosphere. TRAPPIST-1 c? Much the same. Though thought to be similar to Venus both in size and amount of radiation from its star, Webb found that TRAPPIST-1 c lacks Venus’s thick carbon dioxide-rich atmosphere. If there is an atmosphere, it’s very thin. A refresher: TRAPPIST-1 c is the second planet from its star, the M dwarf TRAPPIST-1. M dwarf stars are intriguing because they are 10 times as common and two times more likely to have rocky planets than stars like our Sun. TRAPPIST-1 has seven! Young M dwarf stars are energetic, emitting X-ray and UV radiation that can strip young planetary atmospheres away. It’s unknown if systems like these had enough water, carbon dioxide, or other ingredients to make atmospheres when the planets formed. Webb is so sensitive that it can search for elements and molecules like oxygen, nitrogen, and carbon dioxide in exoplanet atmospheres. The mystery remains — can planets orbiting small M dwarfs sustain the atmospheres needed to support life as we know it? Get the full report: www.nasa.gov/feature/goddard/2023/webb-rules-out-thick-ca... This image: This graph compares the measured brightness of TRAPPIST-1 c to simulated brightness data for three different scenarios. The measurement (red diamond) is consistent with a bare rocky surface with no atmosphere (green line) or a very thin carbon dioxide atmosphere with no clouds (blue line). A thick carbon dioxide-rich atmosphere with sulfuric acid clouds, similar to that of Venus (yellow line), is unlikely. Credits: NASA, ESA, CSA, Joseph Olmsted (STScI) Image description: Graphic titled “Rocky Exoplanet TRAPPIST-1 c Emission Spectra, MIRI Time-Series Photometry (F1500W)” showing the brightness of 15-micron light plotted on an xy graph of brightness in percent eclipse depth versus wavelength in microns, with three simulated emission spectra for comparison. The 15-microns MIRI measurement, plotted as a red diamond with white error bars, has an y-value of 0.04 percent eclipse depth. A simulated spectrum of the planet assuming a thin carbon dioxide atmosphere with no clouds, plotted in blue, has a positive slope and a broad, deep valley centered at 15 microns. A simulated spectrum assuming a bare rocky surface with no atmosphere, plotted in green, has a gentler slope and intersects the blue line at 15 microns. A simulated spectrum assuming a Venus-like atmosphere, plotted in yellow, has a very gentle slope. The red diamond plots just above the blue and green lines, but far above the yellow. In the background is an illustration of the planet and its star. Image & Description by NASA