Scientists have detected a mysterious dark spot on Neptune from Earth for the first time.

The large, dark area is within Neptune’s atmosphere and next to an unexpected, smaller bright spot, experts have said.

Spots are common on giant planets – the most famous being Jupiter’s Great Red Spot – but experts say this is the first time one has been seen on Neptune with a telescope from Earth.

They remain a mystery to astronomers, who are hoping the new discovery will provide clues as to what causes them.

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Michael Wong, a researcher at the University of California, said: “This is an astounding increase in humanity’s ability to observe the cosmos.

“At first, we could only detect these spots by sending a spacecraft there, like Voyager.

“Then we gained the ability to make them out remotely with Hubble. Finally, technology has advanced to enable this from the ground.”

A dark spot was first discovered on Neptune by NASA’s Voyager 2 in 1989, before disappearing a few years later.

Patrick Irwin, professor at the University of Oxford and lead investigator of the study, said: “Since the first discovery of a dark spot, I’ve always wondered what these short-lived and elusive dark features are.”

The scientists have seen the spot for themselves by using the European Southern Observatory’s (ESO) Very Large Telescope (VLT).

The researchers used data from the VLT to rule out the possibility that dark spots are caused by a clearing in the clouds.

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Their research, published in Nature Astronomy, began after NASA and the European Space Agency’s Hubble Space Telescope discovered several dark spots in the planet’s atmosphere, including one in Neptune’s northern hemisphere in 2018.

They’ve been able to learn more by splitting the sunlight reflected from the planet and observations suggest the natural phenomena could be caused by air particles darkening as ice and hazes mix in Neptune’s atmosphere.

The spectrum method astronomers used helped them determine how high the current dark spot sits in the atmosphere, as well as revealing the chemical composition of different layers in Neptune’s atmosphere.

The observations also offered up a surprise result – a rare deep bright cloud type that had never been identified before, even from space.

This rare cloud type appeared as a bright spot right beside the larger main dark spot.