NASA's Next Great Observatory Could Spot Oceans on Distant Worlds

NASA's new research suggests that it may be possible to detect liquid oceans on distant exoplanets by observing "glint," a phenomenon that occurs when light reflects off water at a shallow angle. The study, conducted by Eleanor Cornish and Tyler Robinson of the University of Arizona, uses a modified atmospheric tool called rfast to detect glint. The tool incorporates the Cox-Munk ocean model to account for how wind speeds and wave ripples affect light reflection. The researchers found that even at relatively high noise thresholds, the model could differentiate between planets with and without oceans, provided they were viewed at a phase angle of more than 120°. This is significant because it means that telescopes could potentially detect glint from exoplanets, even if they are far away.

The study highlights that glint is not only possible but has been observed on Earth and Titan, but it has not yet been applied to exoplanets. The researchers modified the tool to make it suitable for detecting glint on exoplanets, and their model proved it could distinguish between planets with and without oceans. The findings suggest that the Habitable Worlds Observatory (HWO), a planned telescope, could potentially detect ocean glint from exoplanets, provided they are viewed at the correct phase angle. The tool's ability to operate at a phase angle of more than 120° allows for some breathing room in the design, but it also highlights the challenges of detecting glint on planets with cloud cover.

The study acknowledges that there are limitations in their model, particularly with cloud cover. They assumed 50% cloud cover for an Earth-like world, but real-world planets can have much more cloud cover. The researchers also note that without a lot of data about Earth's crescent phase, it will be difficult to train the tool for future observations. However, the study is a significant step forward in the quest to find liquid oceans on distant worlds.

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