Astronomers found that the dark spots are likely the result of particles darkening
Astronomers observed a mysterious dark spot in Neptune's atmosphere for the first time from Earth. The observation was made using the European Southern Observatory's Very Large Telescope (VLT) in Chile.
The astronomers also discovered an unexpected smaller bright spot adjacent to the dark spot.
The space-based observatory says that this is the first time a dark spot on Neptune has ever been observed using a telescope on Earth. New observations are published in the journal Nature Astronomy.
Notably, large spots are common among gas giants. You might have already heard about the famous great red spot on Jupiter. According to New Scientist, NASA's Voyager 2 space probe detected a shadowy region on Neptune in 1989, which was dubbed the "Great Dark Spot". After this, the Hubble Space Telescope said that these marks are quite common and tend to disappear after a few years.
"Since the first discovery of a dark spot, I've always wondered what these short-lived and elusive dark features are," said lead study author Patrick Irwin, professor of planetary physics at the University of Oxford, in a statement.
However, the origin of these spots remains a mystery. The researchers have ruled out one possibility that the dark spots are caused by "clearings" in the cloud. The researchers said that the dark spots could be the result of air particles darkening in a layer below the main visible layer of the atmosphere.
"In the process, we discovered a rare deep bright cloud type that had never been identified before, even from space," said study co-author Michael Wong in a press statement. Mr Wong is a researcher at the University of California, Berkeley, USA.
The unusual cloud appeared in the observation as a smaller bright spot next to the larger dark spot, and both were on the same atmospheric level. The astronomers said they are intrigued by the newly discovered feature and hope to learn more with future observations that can be conducted from Earth, CNN reported.
"This is an astounding increase in humanity's ability to observe the cosmos," Mr Wong said. "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."