NASA scientists stunned after discovering mysterious 'skull hill' on Mars

Our closest planet is full of many wonders and mysteries, most of which we're still uncovering.

Last month, NASA’s Curiosity rover detected the largest organic compounds ever found on Mars, which could indicate signs of Martian life.

Also, earlier this month, scientists were left baffled after NASA’s Perseverance rover discovered a bizarre rock on Mars, containing hundreds of millimetre-sized marbles packed together in an alien-like mass.

Now, the US space agency has been stumped again after coming across a weird rock on the Red Planet that looks suspiciously like a 'skull.'

The photo of the eerie-looking rock was taken by the Perseverance rover, which has been exploring Mars for over four years and sending photos back to Earth.

NASA’s Mars Perseverance rover shows the ‘Skull Hill’ target. (NASA/JPL-Caltech/ASU)

Captured by Mastcam-Z, the raised camera, the rover made its way down a slope known as Witch Hazel Hill in the Jezero Crater.

Coincidentally, this wasn't not too far from where a creepy 'face' rock was spotted back in 1976.

The jagged-shaped rock seemingly stands out in the photo, darker than the surrounding reddish terrain and covered in tiny pits - hence the 'skull' reference.

It’s not the first dark rock Perseverance has come across in the Port Anson region, but this one’s unique. The US space agency suspects that the rock may have broken off from a 'nearby outcrop or ejected from an impact crater.'

According to NASA's blog post, minerals like 'olivine, pyroxene, amphibole, and biotite' can give these rocks their dark colour.

Along the way, the rover also came across a bunch of similar rocks that likely didn’t form where they were found, known as 'float' rocks.

There's still so much to uncover about our neighbouring planet. (SCIEPRO/SCIENCE PHOTO LIBRARY/Getty)

"We’ve found a few of these dark-toned floats in the Port Anson region, and the team is working to better understand where these rocks came from and how they got here," PhD student Margaret Deahn explained the finding.

Deahn added that while the rock’s dark colour is similar to meteorites previously found on Mars, early analysis of similar rocks suggests it’s not one. Another possibility is that it could be an igneous rock, formed when magma or lava cools down after being released from volcanoes.

NASA added in its blog post: "On Earth and Mars, iron and magnesium are some of the main contributors to igneous rocks, which form from the cooling of magma or lava.

"Luckily for us, the rover has instruments that can measure the chemical composition of rocks on Mars. Understanding the composition of these darker-toned floats will help the team to interpret the origin of this unique rock!"