Biosignatures & Paleobiology

High-Resolution Transmission Spectra of Earth through Geological Time

By Keith Cowing
Press Release
January 2, 2020
Filed under
High-Resolution Transmission Spectra of Earth through Geological Time
Temperature and mixing ratios for major atmospheric gases in our model atmospheres, representative of 5 epochs through Earth’s geological evolution from an CO2-rich prebiotic atmosphere for Earth around 3.9Ga to an anoxic atmosphere around 3.5Ga and 3 models, which capture the rise of oxygen from 0.01PAL O2 to 1PAL (21% O2) on modern Earth. The mixing ratios shown from left to right are for H2O, CH4, O3 and N2O

The next generation of ground- and space-based telescopes will be able to observe rocky Earth-like planets in the near future, transiting their host star. We explore how the transmission spectrum of Earth changed through its geological history.

These transmission spectra provide a template for how to characterize an Earth-like exoplanet – from a young prebiotic world to a modern Earth. They also allow us to explore at what point in its evolution a distant observer could identify life on our Pale Blue Dot and other worlds like it. We chose atmosphere models representative of five geological epochs of Earth’s history, corresponding to a prebiotic high CO2-world 3.9 billion years ago (Ga), an anoxic world around 3.5 Ga, and 3 epochs through the rise of oxygen from 0.2 percent to present atmospheric levels of 21 percent.

Our transmission spectra show atmospheric spectral features, which would show a remote observer that Earth had a biosphere since about 2 billion years ago. These high-resolution transmission spectral database of Earth through geological time from the VIS to the IR is available online and can be used as a tool to optimize our observation strategy, train retrieval methods, and interpret upcoming observations with JWST, the Extremely Large Telescopes and future mission concepts like Origins, HabEx, and LUOVIR.

Lisa Kaltenegger, Zifan Lin, Jack Madden
(Submitted on 24 Dec 2019)
Comments: in review ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1912.11149 [astro-ph.EP] (or arXiv:1912.11149v1 [astro-ph.EP] for this version)
Submission history
From: Lisa Kaltenegger
[v1] Tue, 24 Dec 2019 00:03:03 UTC (546 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻