Was There a Huge Ocean on Mars? A Look at New Evidence

A new theory about the origin of boulder fields strewn across the northern Martian landscape may add to a body of evidence that an ocean once covered a large portion of the planet.

Lorena Moscardelli, a geologist at the University of Texas, published a study in the Geological Society of America’s journal, GSA Today, this month suggesting that the boulders were dragged into place by landslides on the ocean floor.

This phenomenon has been studied across Earth’s landscape. For example, large sandstone blocks known as the Jackfork Group remain in what was once an ocean basin in south-central Arkansas. 

Moscardelli contests the alternative theory that the boulders on Mars were deposited by meteorites. She noted that there are no impact craters in some areas. “While the meteorite impact hypothesis can certainly explain the occurrence of some of the boulders observed on the northern plains of Mars, especially those that occur in close proximity to impact craters, it does not provide a comprehensive mechanism to understand the wide distribution of boulders in these regions,” she wrote.

Her theory about the boulders should be taken in the context of mounting evidence for a Martian ocean, and not as a singular proof, she said.

In July 2013, researchers at Caltech found what they said could be the most convincing evidence for a Martian ocean to date. Studying a riverbed in the north with detailed topographical mapping technology, they found the river likely fed into a delta.

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