Cassini radar sees sand dunes on Saturn’s giant moon Titan (upper photo) that are sculpted like Namibian sand dunes on Earth (lower photo). The bright features in the upper radar photo are not clouds but topographic features among the dunes. Credit: NASA

Titan, Saturn’s largest moon, is a peculiar place. Unlike any other moon, it has a dense atmosphere. It has rivers and lakes made up of components of natural gas, such as ethane and methane. It also has windswept dunes that are hundreds of yards high, more than a mile wide and hundreds of miles long—despite data suggesting the body to have only light breezes.

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Dr. Robert Riding, research professor in Earth and Planetary Sciences at the University of Tennessee, received a write-up in New Scientist last week for a discovery he and his colleagues made while analyzing rock samples collected from Steep Rock Lake in Ontario, Canada. 

Riding’s team found that the limestone from which the samples were taken had not changed in 2.8 billion years. For limestone to form, calcium carbonate must be stripped of all its dissolved iron — a process which can only happen if oxygen is present. 

Why is this important? Because oxygen levels didn’t increase on a worldwide scale until 2.4 billion years ago. This is the first evidence of an “oxygen oasis,” which could have helped early life develop a tolerance to the poisonous gas. 

Read more at New Scientist or read Dr. Riding’s research, “Identification of an Archean marine oxygen oasis.”