NASA recently revealed that the James Webb Space Telescope, the world’s leading space science observatory, managed to capture the first clear evidence of carbon dioxide in the atmosphere of a planet outside the solar system. The exoplanet in question, WASP-39b, is a hot gas giant with a mass about a quarter of Jupiter’s mass (about the same as Saturn’s) and a diameter 1.3 times that of Jupiter. It orbits very close to its star — barely an eighth of the distance between the Sun and Mercury — and completes a circuit in just over four Earth days. Although it was previously detected by NASA’s Spitzer Space Telescope, which operated between 2003 and 2020, it never detected conclusive data to suggest that in WASP-39b’s atmosphere there might be carbon dioxide, one of the crucial components of Earth’s atmosphere. Now, thanks to Webb’s unparalleled infrared sensitivity and because different gases absorb different color combinations, researchers can analyze some of the starlight that is transmitted through the planet’s atmosphere to determine exactly what its atmosphere is made of.
According to the scientific journal Nature, detecting carbon dioxide in the atmosphere of a planet is “a springboard to the detection of life beyond Earth.” Astronomers don’t expect WASP-39b to be able to harbor life: it’s too close to its star; they don’t even expect the Webb telescope to find definitive signs of life on another planet. But using the Webb to detect carbon dioxide helps lay the groundwork for future discoveries. Specifically, a mixture of carbon dioxide and methane in a planet’s atmosphere could be an indicator of life, which is known as a biological signature. Natalie Batalha, who leads Webb’s Transiting Exoplanet Early Release Science team and is a co-author of the study they are about to publish with these new findings, argues that ultimately, the detection of life will likely require an observatory even more advanced than the Webb; however, “this is a really important phase that we need to go through to be prepared for that technology in the future.”
