Is there life out there among the stars? No one knows for sure, but we’re constantly finding new exoplanets that have some potential to harbor life. Astronomers don’t currently have the technology to examine these distant objects directly, but we may be able to learn about their atmospheres. This could help determine if there’s life present, but a new analysis suggests an exoplanet’s atmosphere might not tell us as much as we thought.
Researchers from the Max Planck Institute for Astronomy in Germany created simulations of multiple nearby exoplanets that have the potential to support life, including Proxima b and TRAPPIST-1d. Like many exoplanets, these worlds are tidally locked to their stars. That means they do not rotate like Earth, leaving one side permanently in the light and the other forever dark. This property could make it much more difficult to know if there’s anything alive on the surface.
Astronomers hope to use instruments like the upcoming Webb Space Telescope to examine the atmospheres of exoplanets. This is something we’ve been able to do on occasion in very limited circumstances with existing technology. By looking for certain biomarkers, it’s possible to get an idea whether life as we know it exists on a planet. One molecule researchers want to look for is ozone, which could indicate oxygen-producing biological activities are happening on a planet. However, a tidally locked world may not distribute ozone in a way we can detect.
According to the new models, atmospheric currents on a tidally locked planet would flow from the poles in toward the equator. That could push most of the ozone into a narrow band and trap it there. This would make it difficult to detect, so an exoplanet with biological ozone in its atmosphere could end up looking just like a lifeless exoplanet based on our observations.
While this could spell trouble for detecting life on some exoplanets, not all of them are going to be tidally locked. Indeed, these are probably less likely to be home to extraterrestrial life in the first place. The same weather pattern that hides ozone could also make the surface uninhabitable. Without proper ozone coverage, UV radiation from the host star could fry anything we think of as life.
NASA is currently scheduled to launch the Webb Telescope in early 2019. We should have a better idea if the models hold up once it comes online and begins sending back data.
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