Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes?
The search for signs of life on other worlds has largely focused on terrestrial planets. Recent work, however, argues that life could exist in the atmospheres of temperate sub-Neptunes. Here we evaluate the usefulness of carbon dioxide isotopologues as evidence of aerial life. Carbon isotopes are of...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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American Astronomical Society
2023
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| Online Access: | https://hdl.handle.net/1721.1/148478 |
| _version_ | 1826192645288886272 |
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| author | Glidden, Ana Seager, Sara Huang, Jingcheng Petkowski, Janusz J Ranjan, Sukrit |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Glidden, Ana Seager, Sara Huang, Jingcheng Petkowski, Janusz J Ranjan, Sukrit |
| author_sort | Glidden, Ana |
| collection | MIT |
| description | The search for signs of life on other worlds has largely focused on terrestrial planets. Recent work, however, argues that life could exist in the atmospheres of temperate sub-Neptunes. Here we evaluate the usefulness of carbon dioxide isotopologues as evidence of aerial life. Carbon isotopes are of particular interest, as metabolic processes preferentially use the lighter 12C over 13C. In principle, the upcoming James Webb Space Telescope (JWST) will be able to spectrally resolve the 12C and 13C isotopologues of CO2, but not CO and CH4. We simulated observations of CO2 isotopologues in the H2-dominated atmospheres of our nearest (<40 pc), temperate (equilibrium temperature of 250–350 K) sub-Neptunes with M-dwarf host stars. We find 13CO2 and 12CO2 distinguishable if the atmosphere is H2 dominated with a few percentage points of CO2 for the most idealized target with an Earth-like composition of the two most abundant isotopologues, 12CO2 and 13CO2. With a Neptune-like metallicity of 100× solar and a C/O of 0.55, we are unable to distinguish between 13CO2 and 12CO2 in the atmospheres of temperate sub-Neptunes. If atmospheric composition largely follows metallicity scaling, the concentration of CO2 in a H2-dominated atmosphere will be too low to distinguish CO2 isotopologues with JWST. In contrast, at higher metallicities, there will be more CO2, but the smaller atmospheric scale height makes the measurement impossible. Carbon dioxide isotopologues are unlikely to be useful biosignature gases for the JWST era. Instead, isotopologue measurements should be used to evaluate formation mechanisms of planets and exosystems. |
| first_indexed | 2024-09-23T09:27:04Z |
| format | Article |
| id | mit-1721.1/148478 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T09:27:04Z |
| publishDate | 2023 |
| publisher | American Astronomical Society |
| record_format | dspace |
| spelling | mit-1721.1/1484782023-03-11T03:45:57Z Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? Glidden, Ana Seager, Sara Huang, Jingcheng Petkowski, Janusz J Ranjan, Sukrit Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences The search for signs of life on other worlds has largely focused on terrestrial planets. Recent work, however, argues that life could exist in the atmospheres of temperate sub-Neptunes. Here we evaluate the usefulness of carbon dioxide isotopologues as evidence of aerial life. Carbon isotopes are of particular interest, as metabolic processes preferentially use the lighter 12C over 13C. In principle, the upcoming James Webb Space Telescope (JWST) will be able to spectrally resolve the 12C and 13C isotopologues of CO2, but not CO and CH4. We simulated observations of CO2 isotopologues in the H2-dominated atmospheres of our nearest (<40 pc), temperate (equilibrium temperature of 250–350 K) sub-Neptunes with M-dwarf host stars. We find 13CO2 and 12CO2 distinguishable if the atmosphere is H2 dominated with a few percentage points of CO2 for the most idealized target with an Earth-like composition of the two most abundant isotopologues, 12CO2 and 13CO2. With a Neptune-like metallicity of 100× solar and a C/O of 0.55, we are unable to distinguish between 13CO2 and 12CO2 in the atmospheres of temperate sub-Neptunes. If atmospheric composition largely follows metallicity scaling, the concentration of CO2 in a H2-dominated atmosphere will be too low to distinguish CO2 isotopologues with JWST. In contrast, at higher metallicities, there will be more CO2, but the smaller atmospheric scale height makes the measurement impossible. Carbon dioxide isotopologues are unlikely to be useful biosignature gases for the JWST era. Instead, isotopologue measurements should be used to evaluate formation mechanisms of planets and exosystems. 2023-03-10T19:03:31Z 2023-03-10T19:03:31Z 2022 2023-03-10T18:59:37Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/148478 Glidden, Ana, Seager, Sara, Huang, Jingcheng, Petkowski, Janusz J and Ranjan, Sukrit. 2022. "Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes?." Astrophysical Journal, 930 (1). en 10.3847/1538-4357/AC625F Astrophysical Journal Creative Commons Attribution 4.0 International license https://creativecommons.org/licenses/by/4.0/ application/pdf American Astronomical Society The American Astronomical Society |
| spellingShingle | Glidden, Ana Seager, Sara Huang, Jingcheng Petkowski, Janusz J Ranjan, Sukrit Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? |
| title | Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? |
| title_full | Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? |
| title_fullStr | Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? |
| title_full_unstemmed | Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? |
| title_short | Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes? |
| title_sort | can carbon fractionation provide evidence for aerial biospheres in the atmospheres of temperate sub neptunes |
| url | https://hdl.handle.net/1721.1/148478 |
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