Scientists have got chatting once again about the dark holes spotted right across the surface of Mars, with renewed hope they could help provide the answers to alien life in the universe and better understand the planet's history.
Fascinating to the eye, they aren't a new phenomenon. Images of them have been captured for almost two decades now, going back to 2007.
But thanks to the University of Arizona HiRISE's Picture of the Day, they've resurfaced in the psyche of the online space community.
And that's because we know very little about how they came about and as a result, produce almost limitless conversation about what they could help humanity understand about Mars and the wider planet.
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What are the holes?
The holes on the surface of Mars can be found on the flanks of one ancient volcanoes in Mars' Tharsis region.
It's the most volcanic region of the planet and in fact provide some of the largest volcanoes in the entire solar system. Better luck next time, Mount Fuji.
But much like Mount Thielsen in Oregon, Mars is thought to no longer be volcanically active.
What's inside the holes?
According to astronomers and experts in the field of volcanoes, there is a big hunch that the holes are connected to the nearby volcanoes.
Speaking to Business Insider (BI), Brandon Johnson, a geophysicist at Purdue University, said they are likely 'skylights'. In other words, they would have acted as places where the ground above lava tubes caved in due to the lava tubes no longer being active.
How could the holes help humanity?
On one front, the holes could play a big part in helping future manned missions to Mars, with them being a safe haven for astronauts to shelter from radiation and solar storms.
Johnson said: "There's more than one of these pits on Mars that we've seen.
"But they're really interesting because they're places where astronauts might be able to go and be safe from radiation."
The big question, of course, is how deep do the holes go. Ross Beyer told BI that the 'pits we see could open into larger caves, or they could just be isolated pits'.
And what about life on Mars?
The big question, and one the late David Bowie would certainly like an answer to.
Firstly there is no guarantee that there is any life on Mars. But what these holes do is give us access to Mars beneath its surface.
There, it could be like a whole other world when it comes to accessing potential ancient organic matter.
With lava tubes on the Moon getting as warm as 17C, there is reason to hope this could also be the case for Mars.
Topics: Aliens, Space, Technology, Weird
Tom Earnshaw