LHS 1140 b is a potentially habitable water world
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866929694134239232 |
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| author | Damiano, Mario Bello-Arufe, Aaron Yang, Jeehyun Hu, Renyu |
| author_facet | Damiano, Mario Bello-Arufe, Aaron Yang, Jeehyun Hu, Renyu |
| contents | LHS 1140 b is a small planet orbiting in the habitable zone of its M4.5V dwarf host. Recent mass and radius constraints have indicated that it has either a thick H$_2$-rich atmosphere or substantial water by mass. Here we present a transmission spectrum of LHS 1140 b between 1.7 and 5.2 $μ$m, obtained using the NIRSpec instrument on JWST. By combining spectral retrievals and self-consistent atmospheric models, we show that the transmission spectrum is inconsistent with H$_2$-rich atmospheres with varied size and metallicity, leaving a water world as the remaining scenario to explain the planet's low density. Specifically, a H$_2$-rich atmosphere would result in prominent spectral features of CH$_4$ or CO$_2$ on this planet, but they are not seen in the transmission spectrum. Instead, the data favors a high-mean-molecular-weight atmosphere (possibly N$_2$-dominated with H$_2$O and CO$_2$) with a modest confidence. Forming the planet by accreting C- and N-bearing ices could naturally give rise to a CO$_2$- or N$_2$-dominated atmosphere, and if the planet evolves to or has the climate-stabilizing mechanism to maintain a moderate-size CO$_2$/N$_2$-dominated atmosphere, the planet could have liquid-water oceans. Our models suggest CO$_2$ absorption features with an expected signal of 20 ppm at 4.2 $μ$m. As the existence of an atmosphere on TRAPPIST-1 planets is uncertain, LHS 1140 b may well present the best current opportunity to detect and characterize a habitable world. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_13265 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | LHS 1140 b is a potentially habitable water world Damiano, Mario Bello-Arufe, Aaron Yang, Jeehyun Hu, Renyu Earth and Planetary Astrophysics LHS 1140 b is a small planet orbiting in the habitable zone of its M4.5V dwarf host. Recent mass and radius constraints have indicated that it has either a thick H$_2$-rich atmosphere or substantial water by mass. Here we present a transmission spectrum of LHS 1140 b between 1.7 and 5.2 $μ$m, obtained using the NIRSpec instrument on JWST. By combining spectral retrievals and self-consistent atmospheric models, we show that the transmission spectrum is inconsistent with H$_2$-rich atmospheres with varied size and metallicity, leaving a water world as the remaining scenario to explain the planet's low density. Specifically, a H$_2$-rich atmosphere would result in prominent spectral features of CH$_4$ or CO$_2$ on this planet, but they are not seen in the transmission spectrum. Instead, the data favors a high-mean-molecular-weight atmosphere (possibly N$_2$-dominated with H$_2$O and CO$_2$) with a modest confidence. Forming the planet by accreting C- and N-bearing ices could naturally give rise to a CO$_2$- or N$_2$-dominated atmosphere, and if the planet evolves to or has the climate-stabilizing mechanism to maintain a moderate-size CO$_2$/N$_2$-dominated atmosphere, the planet could have liquid-water oceans. Our models suggest CO$_2$ absorption features with an expected signal of 20 ppm at 4.2 $μ$m. As the existence of an atmosphere on TRAPPIST-1 planets is uncertain, LHS 1140 b may well present the best current opportunity to detect and characterize a habitable world. |
| title | LHS 1140 b is a potentially habitable water world |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2403.13265 |