Research indicates that the prospect of TRAPPIST-1e, an exoplanet, harboring an atmosphere similar to Venus or Mars is highly improbable.

The first author of a new study, Ana Glidden from the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) and the MIT Kavli Institute for Astrophysics and Space Research, has shared that initial observations with the James Webb Space Telescope (JWST) have showcased its potential in understanding the atmosphere of TRAPPIST-1e, a compelling habitable-zone planet.

TRAPPIST-1e, located in the TRAPPIST-1 system, remains one of the most intriguing candidates for a potentially habitable planet. The researchers compared the JWST's findings to several different possible atmospheric scenarios.

JWST's improved observations allow for the detection of molecules like carbon dioxide and methane, commonly found in our own solar system. However, carbon dioxide-rich atmospheres, similar to those of Mars and Venus, are unlikely for TRAPPIST-1e.

The researchers used a novel approach to mitigate for stellar activity, allowing them to distinguish signals from the star and the planet. This was crucial as stellar contamination, caused by changes in the host star's temperature due to sunspots and solar flares, poses a challenge in interpreting JWST data.

Exoplanet atmospheres are studied using a technique called transmission spectroscopy. In this method, astronomers determine which molecules are present in an exoplanet's atmosphere by seeing how the light changes at different wavelengths when the planet passes in front of its host star. The data from the JWST were consistent enough to still allow for the possibility of a surface ocean on TRAPPIST-1e.

The current hypothesis suggests that TRAPPIST-1e may have a secondary atmosphere rich in heavy gases like nitrogen, similar to Earth's atmosphere, with potential presence of trace methane (CH4) and possibly some carbon dioxide (CO2) in lower amounts. However, the data are not yet conclusive enough to confirm an atmosphere or rule out the planet being a bare rocky world.

The evidence is too weak to determine if any atmosphere is present on TRAPPIST-1e, let alone detect a specific type of gas. The James Webb Space Telescope (JWST) has improved observations by using near-infrared spectroscopy during transits, detecting subtle absorption features that hint at atmospheric gases but with uncertainties still large enough to keep the null hypothesis (no atmosphere) plausible. Future JWST observations are planned to refine these findings significantly.

A warm, nitrogen-rich atmosphere similar to Saturn's moon Titan remains a possibility for TRAPPIST-1e. Additional, ongoing observations will help to narrow down the possibilities for TRAPPIST-1e's atmosphere.

The study, published today in The Astrophysical Journal Letters, ruled out the possibility of a hydrogen-dominated atmosphere for TRAPPIST-1e. The study's co-authors include collaborators from the University of Arizona, Johns Hopkins University, University of Michigan, the Space Telescope Science Institute, and members of the JWST-TST DREAMS Team.

The JWST, with its larger wavelength coverage and higher spectral resolution than the Hubble Space Telescope, continues to provide valuable insights into the study of exoplanet atmospheres, offering hope for a better understanding of the potential for life beyond our solar system.