Early Titan Was a Cold, Hostile Place

Titan is a mysterious orange-socked moon of Saturn that is exciting to astrobiologists because it has some of the same kinds of chemicals that were precursors to life on Earth. Its atmosphere is 95 percent nitrogen, but it also has a tad bit of methane, predominantly close to the surface.

Titan’s methane is thought to be less than a half billion years old, leading astrobiologists to wonder what Titan’s atmosphere looked like early in its history when there was little to no methane present. Could it reflect what Earth might have looked like earlier in our planet’s history before life arrived?

A new study by Benjamin Charnay and colleagues explores this question. According to Charnay, early Titan was most likely a world surrounded by an almost pure and clear nitrogen atmosphere, with a similar surface pressure to today but with a lesser greenhouse effect. Charnay is a planetary scientist who was at the Laboratory of Dynamic Meteorology at the P&M Curie University in France when the research was conducted, and is now post-doctoral researcher with the University of Washington.

“Looking at Titan’s past helps us to understand where the methane comes from and how the photochemistry evolved,” said Charnay. “The photochemistry in Titan’s past with less atmospheric methane may have been closer to the atmospheric chemistry on the early Earth that could have led to the emergence of life.”

Charnay added that if methane was present in Titan around four billion years ago, today there would be large seas of ethane rather than the smaller polar lakes we observe.

The paper, “Titan’s past and future: 3D modeling of a pure nitrogen atmosphere and geological implications,” was published in the journal Icarus