Methane, a chemical compound with the formula CH₄, plays an important role in Project Hail Mary. First, as we discussed in #143, the deliberate release of methane from the ice in Antarctica is pursued as a way to maintain Earth’s heat as the sun dims. Later, Ryland and Rocky discover the methane present in Adrian’s atmosphere, which turns out to be the result of biological processes.

Upon initially detecting Adrian’s methane-rich atmosphere, Rocky states matter-of-factly that “Geology creates methane”. 17.036 Ryland is not entirely convinced of this explanation but fails to propose an alternative hypothesis at the time. Later in the same section, he discovers the abundance of life present in Adrian’s atmosphere and declares that “Life makes methane!” 17.203

Adrian’s methane is produced when Taumoeba consume Astrophage; in other words, the methane-rich atmosphere directly results from Taumoeba poop. Ryland later concludes that they can “Use Taumoeba farts to propel [them]selves through space” 22.127 although Rocky does not understand the word that directly follows “Taumoeba”.

Earth’s atmospheric concentration of methane has more than doubled since pre-industrial times and is a much more powerful greenhouse gas than carbon dioxide. Sources of methane on Earth include metabolic processes of microorganisms, gas release from thawing permafrost, and anthropogenic sources such as fossil fuel extraction and emissions from livestock.

When we discover methane on other worlds in our solar system, however, we generally investigate the same sources that Rocky and Ryland identified: geology and maybe even biology.

The Curiosity Rover detected traces of methane on Mars, though somewhat mysteriously, the concentration of methane fluctuates seasonally and it seems to disappear at night. The methane on Mars could be the result of geological activity, an explanation potentially supported by InSight’s detection of marsquakes and signs of vulcanism. However, a much more exciting possibility would be that microorganisms living below the surface of Mars are producing methane as a metabolic product.

Titan, Saturn’s largest moon, holds large amounts of methane in its atmosphere. The complex chemistry of Titan’s atmosphere even results in occasional methane storms. Even more fascinating are the methane lakes and rivers found on this unusual moon’s surface. A future NASA mission called Dragonfly will explore Titan and assess its habitability.

If we journey over 160 light-years in the direction of the constellation Aquila, there too we find methane, in the atmosphere of an exoplanet called WASP-80 b. In 2023 the James Webb Space Telescope detected methane in this distant gas giant’s atmosphere, emphasizing just how much remains to be discovered about our universe.