Things may not have ended well for dinosaurs on Earth, but Cornell University astronomers say the “light fingerprint” of the conditions that enabled them to emerge here provide a crucial missing piece in our search for signs of life on planets orbiting alien stars.
Their analysis of the most recent 540 million years of Earth’s evolution, known as the Phanerozoic Eon, finds that telescopes could better detect potential chemical signatures of life in the atmosphere of an Earth-like exoplanet more closely resembling the age the dinosaurs inhabited than the one we know today.
Two key biosignature pairs — oxygen and methane, and ozone and methane — appeared stronger in models of Earth roughly 100 million to 300 million years ago, when oxygen levels were significantly higher. The models simulated the transmission spectra, or light fingerprint, generated by an atmosphere that absorbs some colors of starlight and lets others filter through, information scientists use to determine the atmosphere’s composition.
“Modern Earth’s light fingerprint has been our template for identifying potentially habitable planets, but there was a time when this fingerprint was even more pronounced — better at showing signs of life,” said Lisa Kaltenegger, director of the Carl Sagan Institute (CSI) and associate professor of astronomy. “This gives us hope that it might be just a little bit easier to find signs of life — even large, complex life — elsewhere in the cosmos.”
Kaltenegger is co-author of “Oxygen Bounty for Earth-like Exoplanets: Spectra of Earth Through the Phanerozoic,” published in Monthly Notices of the Royal Astronomical Society: Letters. First author, Rebecca Payne, research associate at CSI, led the new models that details a critical epoch including the origins of land plants, animals and dinosaurs.
Using estimates from two established climate models (called GEOCARB and COPSE), the researchers simulated Earth’s atmospheric composition and resulting transmission spectra…