New research presented at the Europlanet Science Congress this week has uncovered astonishing findings beneath the dusty surface of Mars.

The study points to evidence that suggests the Red Planet once hosted vast oceans and towering volcanoes. A team of scientists has detailed the discoveries, which include dense, large-scale structures that have left researchers puzzled.

“These dense structures could be volcanic in origin or could be compacted material due to ancient impacts,” Bart Root of Delft University of Technology said in a press release.

The research identifies approximately 20 enigmatic features scattered around Mars’s north polar cap, including one that intriguingly resembles the shape of a dog.

To uncover the hidden features, researchers employed a sophisticated technique that measures minute changes in the orbits of satellites around Mars. The tiny deviations result from variations in the planet’s gravity field, which are influenced by the distribution of mass beneath the surface, Study Finds reports.

By integrating the gravity data with information from NASA’s InSight mission about Mars’s crust and interior, the team created a comprehensive global density map of the planet. The map showed that the mysterious northern features are significantly denser than their surroundings — approximately 600-800 pounds per cubic meter denser.

The study not only uncovered hidden structures in the northern regions but also offered new insights into Olympus Mons, the largest known volcano in our solar system. Olympus Mons, part of the Tharsis Rise — a huge volcanic plateau — has long intrigued scientists due to its enormous size.

The research team found evidence of a large low-density region deep within Mars, spanning about 1,000 miles across and 700 miles below the surface. This region could be an enormous plume of molten rock, gradually rising toward the surface and providing the Tharsis region with an upward “boost.”