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Alien Oceans Exposed! Scientists Discover Gases That Could Prove Life on Waterworld Planets!

Astrobiology Biosignatures Exoplanets

Recent observations and theoretical modeling suggest that some sub-Neptune exoplanets possess water-rich interiors enveloped by hydrogen-dominated atmospheres, potentially harboring liquid oceans on their surfaces. Inspired by these findings and recent observations from the James Webb Space Telescope (JWST) of the exoplanet K2-18 b, researchers have embarked on the first comprehensive study to model the photochemistry of biogenic sulfur gases on these "Hycean" worlds and evaluate their detectability as biosignatures.

The study hinges on the fact that on Earth, sulfur compounds produced by oceanic life forms are broken down by photochemical reactions before they can accumulate. However, on planets with atmospheres resembling those of early Earth, these compounds might survive long enough to be detected. The new research utilized a combination of 3D general circulation models and 2D photochemical models to predict the distribution and detectability of these gases, particularly dimethyl sulfide (DMS).

Key findings include:

  • DMS and related sulfur gases can accumulate to detectable levels on Hycean planets, but this requires biological sulfur emissions at least 20 times greater than those of modern Earth.
  • Detecting these gases at 3.4 μm wavelength is difficult due to overlap with methane signals. However, detections between 9 and 13 μm in the mid-infrared spectrum appear more promising.
  • The absence of photochemical sinks on the nightside of tidally locked planets facilitates the buildup of these gases.

The researchers also noted the challenges in identifying these biosignatures, as DMS strongly overlaps with methane in certain spectral regions. They suggest that future JWST missions should focus on the mid-infrared range where DMS, ethylene, and ethane have more distinct spectral features.

This groundbreaking research opens new avenues in the search for life beyond Earth, proposing that biogenic sulfur gases could serve as a novel class of biosignature on Hycean worlds, which are planets with potential subsurface oceans beneath thick hydrogen atmospheres. The study not only broadens our understanding of exoplanet atmospheres but also highlights the innovative methods needed to probe these distant worlds. The findings are crucial for future missions aiming to detect signs of life in the universe, marking a significant step forward in astrobiology and planetary science.

Read the paper published in The Astrophysical Journal Letters.