If there\u2019s one chemical that causes excitement in the search for biosignatures on other worlds, it\u2019s methane. It\u2019s not a slam dunk because it has both biotic and abiotic sources. But finding it in an exoplanet\u2019s atmosphere means that planet deserves a closer look. <\/p>\n
<\/p>\n Methane captures scientific attention mainly because of its short duration in a planetary atmosphere. Methane can\u2019t withstand starlight for very long, at least not in terrestrial atmospheres. It succumbs to photodissociation and needs to be replenished continually to maintain its presence in an atmosphere. <\/p>\n If a rocky planet has a lot of methane, then the source has to be massive, making a biotic source likely. On Earth, biological activity creates an enormous amount of methane. Metabolically, methane is not difficult to make. <\/p>\n Methane is common in our Solar System, though not necessarily plentiful. As far as scientists can tell, it\u2019s all abiotic. Processes like serpentinization could explain it. Serpentinization is a natural, abiotic process involving water, carbon dioxide, and the mineral olivine. Olivine is common on Earth and is the primary component of our planet\u2019s upper mantle. We\u2019ve also found it on the Moon, on Mars, and on some asteroids. <\/p>\n Recently, the James Webb Space Telescope detected methane in the atmosphere of WASP-80b, a gas giant about half as massive as Jupiter. WASP-80b orbits a K-type main sequence star about 1.5 billion years old. WASP 80 is about 162 light-years away, and WASP-80b is the only planet detected around the star so far. <\/p>\n Since WASP-80b is a gas giant, then life is ruled out, barring some extreme sci-fi scenarios. But the serpentinization of olivine, the most well-known abiotic source of methane, is also ruled out since WASP-80b is not a rocky planet. But finding it is still interesting. That\u2019s partly because we can now compare the exoplanet to the methane-containing atmospheres of Uranus and Neptune in our own Solar System. That can only help us understand future methane detections better. <\/p>\n A new paper published in the journal Nature presents the detection. It\u2019s titled \u201cMethane throughout the atmosphere of the warm exoplanet WASP-80b.\u201d The lead author is Taylor Bell, a post-doc researcher at the Bay Area Environmental Research Institute. <\/p>\n WASP-80b is a warm Jupiter. Its temperature is about 550 Celsius (1,025 F; 825 K.) So it\u2019s in between hot Jupiters like HD 209458 b (the first transiting exoplanet discovered) and cold Jupiters, like our Solar System\u2019s largest planet. Our Jupiter is about 112 Celsius (235 F; 125 K.) <\/p>\n The temperature is an important point. There\u2019s a dearth of methane detections in exoplanet atmospheres, so at this stage of the game, each detection plays an important role in developing atmospheric theory and guiding follow-up research. WASP-80b\u2019s temperature puts it in \u201can interesting transitional regime where equilibrium chemistry models predict that there should be detectable CH4 and CO\/CO2 features in the planet\u2019s transmission and emission spectra\u2026\u201d the authors of the research explain. <\/p>\n WASP-80b is really close to its red dwarf star and takes only three days to orbit. Because the planet is so far away and so close to its star, even the powerful JWST can\u2019t actually see it. Instead, astronomers used the JWST to study the combined light from the star and the planet in transits and eclipses. <\/p>\n There haven\u2019t been many methane detections in exoplanet atmospheres by telescopes like the Hubble and the Spitzer, which can both observe in infrared, though not like the JWST can. The lack of detections led scientists to develop theoretical explanations of how methane could be depleted in atmospheres. High metallicity, high interior heat flux, and other reasons were explored as methane depletion mechanisms. <\/p>\n Since the JWST has now detected methane, it raises an important question. \u201cHowever, this definitive detection of methane throughout the atmosphere of WASP-80b with low-resolution, JWST spectroscopy raises the question to what extent past non-detections were affected by the sparse wavelength coverage and precision achievable with HST and Spitzer,\u201d the authors write. So if astronomers keep detecting methane in more exoplanet atmospheres, we may have to change our thinking about methane as a biosignature. <\/p>\n \u201cAs we find methane and other gases in exoplanets, we will continue to expand our knowledge about how chemistry and physics work under conditions unlike what we have on Earth, and maybe sometime soon, in other planets that remind us of what we have here at home,\u201d the authors wrote in a NASA blog post. <\/p>\n The researchers explain that finding exoplanets with methane in their atmospheres also helps us understand our own Solar System. \u201cNASA has a history of sending spacecraft to the gas giants in our solar system to measure the amount of methane and other molecules in their atmospheres,\u201d the authors write. \u201cNow, by having a measurement of the same gas in an exoplanet, we can start to perform an \u201capples-to-apples\u201d comparison and see if the expectations from the solar system match what we see outside of it.\u201d<\/p>\n The researchers also say that measuring methane alongside water helps define how and where a planet formed. \u201cFor example, by measuring the amount of methane and water in the planet, we can infer the ratio of carbon atoms to oxygen atoms,\u201d they write. \u201cThis ratio is expected to change depending on where and when planets form in their system.\u201d Astronomers can use this data to determine if a planet formed close to its star or formed further away and then migrated inward. <\/p>\n The JWST likely isn\u2019t done with WASP-80b. This data is from the space telescope\u2019s NIRCam instrument. Future MIRI and NIRCam observations will probe the planet at different wavelengths, which should detect other carbon molecules like carbon monoxide and carbon dioxide. \u201cOur findings lead us to think that we will be able to observe other carbon-rich molecules, such as carbon monoxide and carbon dioxide, enabling us to paint a more comprehensive picture of the conditions in this planet\u2019s atmosphere,\u201d the researchers explain.<\/p>\n While methane catches everyone\u2019s attention because of its link to biology, this research shows us another side to methane. It can help us understand how and where some planets formed and if they migrated. Methane detections in exoplanets will help us build a better overall understanding of exoplanet atmospheres. They can even help us understand our own Solar System, about which we still have so many questions. <\/p>\n The JWST is poised to play a key role in building our knowledge of methane and atmospheres.<\/p>\n \u201cOne thing is clear: the journey of discovery with the James Webb Space Telescope is brimming with potential surprises,\u201d the authors say.<\/p>\n![\"Three](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2023\/11\/Jupiter-temp-ranges.png\")
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