According to a new study, the Earth-like planet closest to a star among the seven planets in the famous TRAPPIST-1 system may be able to maintain a dense atmosphere after all.
Ever since the 2017 discovery of a system of seven densely packed Earth-sized worlds huddled in remarkable harmony just 40 light-years from Earth, astronomers have been trying to determine whether any of them support an atmosphere that is crucial to the emergence of life as we know it.
Previous observations by the space-based
James Webb Space Telescope (JWST) have suggested that all planets in this system would turn out to be barren, airless piles of rock thanks to the harsh, atmosphere-destroying radiation released by their parent star.
A new analysis of JWST data on the planet TRAPPIST-1b suggests that it may have a hazy atmosphere rich in carbon dioxide, and measurements have also shown anomalously high surface temperatures, which may indicate that the planet is volcanically active.
Despite being the most studied planetary system
outside the solar system, detecting atmospheres on its planets has proven challenging. This is due to the unusual characteristics of their tiny and cold parent star, a red dwarf, which can mimic atmospheric signals that are already weak and difficult to detect.
The similarity of TRAPPIST-1b to a satellite of Saturn
Previous JWST measurements of the planet's emission at a single wavelength of 15 micrometers have shown that the presence of a dense carbon dioxide-rich atmosphere is unlikely because carbon dioxide strongly absorbs light at this wavelength and would therefore markedly reduce the observed emission.
Last year, researchers concluded that TRAPPIST-1b was likely a ball of rock whose dark surface had been damaged to the point of being completely uninhabitable by stellar radiation and meteorite impacts.
The new measurements, taken at a different wavelength of 12.8 micrometers, indicate not only a dense, carbon dioxide-rich atmosphere, but also the presence of a highly reflective haze similar to the smog seen on Earth.
The researchers say this haze causes the planet's upper atmosphere to be hotter than the lower atmosphere, creating an environment where carbon dioxide emits light rather than absorbing it, which may explain the lack of the expected dip in previous observations.
Photo: space.com
"One plus one is more than two: having two data points for Trappist-1b now allows us to explore alternative scenarios for its atmosphere, whether it exists or not," says study co-author Leen Decin of KU Leuven in Belgium in a recent press release.
Similar dynamics are known to occur on Saturn's largest satellite Titan, for example, but "The chemistry of TRAPPIST-1b's atmosphere is expected to be very different from Titan or any other rocky body in the solar system," study co-author Mikhil Min of the Netherlands' SRON Space Research Institute said in the same statement. "It is exciting to think that we may have in front of us a type of atmosphere that we have never seen before."
Researchers are now monitoring how heat is redistributed on the planet TRAPPIST-1b as it orbits its parent star, which will help determine the composition of the planet's atmosphere.
"If an atmosphere exists, heat should be distributed from the day side of the planet to the night side," says Michael Gillon, an astronomer at the University of Liege in Belgium who led the international team that discovered the seven TRAPPIST-1 planets. "Without an atmosphere, the redistribution of heat would be minimal."
The new study was described in a paper published early last week on Dec. 16 in the journal Nature Astronomy.