NASA scientists using the High Resolution Imaging Science Experiment (HiRISE) camera on board the Mars Reconnaissance Orbiter have captured an image of an enigmatic landform in Athabasca Valles, in the Elysium Planitia region of equatorial Mars.

The circular feature is about 2 km wide. It looks like a circular ‘island’ surrounded by a ‘sea’ of smooth-looking lava flows.

The region where the ‘island’ was spotted is called the Athabasca Valles. It is a geologically young 300-km-long outflow channel system located in north-central Elysium Planitia.

It contains some of the youngest lava flows on the planet and is thought to be 500 to 100 million years old (Late Amazonian).

According to the scientists, the Athabasca Valles’ floor is covered with hundreds of rings and cones formed as steam exploded through the lava flow.

However, they don’t know exactly what the newly-discovered circular mound is.

“It is highly possible that volcanism played a role in creating this feature,” they said.

“Perhaps lava has intruded underneath this mound and pushed it up from beneath.”

It looks as if material is missing from the mound, so it is also possible that there was a significant amount of ice in the mound that was driven out by the heat of the lava.

There are an array of features like this in the region that continue to puzzle scientists.

“We hope that close inspection of this image, and others around it, will provide some clues regarding its formation,” the scientists concluded.