We are here. We’re not entirely sure how we got here, but we are here. But… what if we weren’t here? That’s the question scientists posed in a new study, which simulates an alternative vision of Earth where life, uh, never found a way. The findings, reported in The Planetary Science Journal, are not just a surreal thought experiment. It is also a serious scientific question and a new investigation of the ideas behind the Gaia hypothesis. The Gaia Hypothesis – not to be confused with the mythological hypothesis The similar-sounding Theia Hypothesis proposes that life on Earth interacts with the planet’s physical environment in ways that help maintain a habitable world, producing a kind of planetary homeostasis. In the new research, led by astrobiologist Samantha Gilbert-Janizek of the University of Washington, scientists turned back the clock to see how Earth could develop over billions of years, without any hypothetical help. Does the Earth need life to be habitable? A new simulation shows how the planet could have evolved in the absence of life. (NASA Earth Observatory image by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA Goddard Space Flight Center) “An open question about the evolution of Earth is whether or not it could be habitable on time scales of billions of years without the influence of life in the environment,” the researchers write in their paper. planet?”In their study, Gilbert-Janizek and his colleagues developed a sophisticated computer model of an Earth without life, but incorporating everything else in its physical environment (including the planet’s core, mantle, crust, atmosphere, oceans, and incoming solar flux), and calculated how chemicals would circulate between different parts of the planet. In total, they simulated 19 key planetary properties, such as heat flow, ocean chemistry, and surface temperatures, and tracked how this Earth “This model can help us see how habitable but non-living planets might mimic living planets,” says Gilbert-Janizek. We interpret observations of an exoplanet’s atmosphere, this tool will help us determine the probability that what “In terms of the lifeless surface of the simulated abiotic Earth, it turns out that the absence of life does not seem to make much difference in how things develop over billions of years, with the most striking exception being the lack of atmospheric oxygen, given the absence of photosynthesis. While atmospheric oxygen might be considered non-negotiable for more complex life, it is actually not a prerequisite for habitability in the context of astronomy, where it is generally defined by a planet’s surface ability to support liquid water on its surface. In that sense, the lifeless Earth exhibited water levels similar to those of our own Earth, among other things. “The findings do not refute the Gaia hypothesis, and the researchers note that they cannot rule out the possibility that life on Earth contributes to processes that enhance climate stability. The researchers also acknowledge several limitations and simplifications in their model, including assumptions about plate tectonics, atmospheric chemistry, and the processes that regulate Earth’s climate. However, their simulation results suggest that life is not a requirement for a rocky planet to remain habitable. “Our findings suggest that the abiotic Earth could evolve to a state similar (in terms of global geophysics and climate) to the current Earth without life, but without abundant atmospheric oxygen,” the researchers conclude. “This work thus contributes to the ongoing debate about the Gaia hypothesis by suggesting that life and habitability may be somewhat decoupled.” The findings are published in The Planetary Science Journal. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we take pride in our process, we are human. If you spot an error, please let us know.
