NASA scientists have identified a puzzling cluster of holes etched into the Martian surface, adding a fresh mystery to the long-running exploration of the Red Planet.
The unusual formations were spotted as NASA’s Curiosity rover continued its gradual climb through Valle Grande, a wide valley that slices across Mount Sharp in Mars’ Gale Crater.
Small pits are not rare on Mars, a world heavily scarred by meteorite strikes and harsh surface processes. But researchers say these newly observed features do not yet have a clear explanation.
What makes the Valle Grande holes stand out is their shape: spread across exposed bedrock, they appear wide, shallow and, according to scientists, “unlike quite anything we have seen in the past.”
Dr Michelle Minitti, deputy principal investigator for Curiosity’s Mars Hand Lens Imager, reflected on the find in a mission blog post, writing: “After Curiosity’s 14 years on the surface, Mars continues to surprise.”
She added: ‘They were a welcome new puzzle into the processes that have affected this particular section of rocks.’
NASA has discovered a series of mysterious holes punched into the surface of Mars (pictured), and scientists have no idea what formed them
On both Earth and Mars, small holes worn into the bedrock are a relatively common discovery.
These typically form when a tough pebble or intrusion gets stuck in a bed of softer rock.
When these resistant intrusions are eventually weathered out of the softer surrounding rock, they leave small impressions behind.
However, NASA scientists were stumped when they discovered none of the normal signs of this familiar process.
Dr Minitti wrote: ‘The pits of this week were much broader and shallower than past features and were not accompanied by obvious objects that were once in the pits.’
The Curiosity rover was instructed to use the Mars Hand Lens Imager (MAHLI) to photograph the pits from close range.
Meanwhile, the Mastcam camera took a series of overlapping images of the surrounding terrain.
Combined, these images will allow scientists to make a full three-dimensional map of the pits and to measure their shapes and depth.
The broad pits were found on the slopes of Mount Sharp, a vast mountain formed inside a dried-out lake on the Martian surface
The researchers hope that this should shed some light on how these enigmatic pits came to be dotted over the flanks of Mount Sharp.
It may be that the holes were formed by an unusual property of the surrounding rock, a previously unknown erosion process, or some entirely other factor.
However, that research will take time, meaning scientists currently have no idea how these holes were formed.
Nor were the holes the only mystery encountered by Curiosity in this part of the Martian mountain.
The researchers also noticed rapid changes in appearance between nearby layers of rock bed, including tough grey areas that resist erosion differently from their surroundings.
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NASA suggests that this could be evidence of rapid changes in the conditions under which these layers of rock were laid down millions or even billions of years ago.
Curiosity was directed to sample the chemistry of these unusual layers, but further analysis will take more time.
Scientists are particularly interested in this area of the Martian surface because it could unlock the secrets of the Red Planet’s distant past.
NASA says that Mount Sharp’s sedimentary layers are a ‘history book’ recording the Red Planet’s distant past, which could reveal whether it ever hosted life
The Gale Crater is believed to have been formed around three billion years ago when a massive asteroid collided with the Martian surface.
At its centre is Mount Sharp, which rises about 3.4 miles (5.5km) above the floor of Gale Crater.
NASA says the mountain’s sedimentary layers are a ‘history book of sequential chapters recording environmental conditions when each stratum was deposited’.
Even more excitingly, experts believe that Gale Crater was filled with water after it formed before eventually drying out some time in the past.
Scientists, therefore, believe that the crater could be one of the best places to find evidence of life that could have survived during the planet’s warm, wet past.