Published: Thu, March 28, 2019
Research | By Raquel Erickson

Hubble Captures Formation of Great Dark Spot on Neptune | Astronomy

Hubble Captures Formation of Great Dark Spot on Neptune | Astronomy

Scientists are closer to understanding the big "Dark Spot" storms which form on theice giant Neptune, after the Hubble Space Telescope captured one forming.

Like gas giant Jupiter's Great Red Spot, Neptune's Great Dark Spots are storms forming in areas of high atmospheric pressure in contract to storms on Earth, which form around areas of low pressure.

The Hubble Space Telescope has captured the birth of one of Neptune's mysterious short-lived storms, which can grow to be larger than planet Earth before dying out in a matter of years.

Scientists have seen a total of six dark spots on Neptune over the years.

This bulls-eye view of Neptune's small dark spot D2 was obtained by NASA's Voyager 2 narrow-angle camera on August 24, 1989.

The first two storms were captured by the Voyager 2 probe in 1989, with Hubble capturing the other four. They discovered that the clouds were the most bright in 2016 and 2017, before the new great dark spot became visible in 2018. The fact that they appeared two years before the Great Dark Spot and then lost some brightness when it became visible suggests dark spots may originate much deeper in Neptune's atmosphere than previously thought, the team explains.

By peering through the lens of the Hubble Space Telescope, NASA researchers have captured one of Neptune's storms at is was brewing. It is about 8,000 miles by 4,100 miles (13,000 km by 6,600 km) in size - as large along its longer dimension as the Earth. While Jupiter's Great Red Spot is infamous, Neptune's dark blue spots were unknown until Voyager 2 flew past in 1989, sending back pictures of two large storms on its surface.


The new findings have implications for studying exoplanets of similar size and composition. "If you study the exoplanets and you want to understand how they work, you really need to understand our planets first", stated Simon. "Every time we get new images from Hubble, something is different than what we expected", said Dr. Simon, first author of a paper published in the journal Geophysical Research Letters.

In the Voyager image, a storm known as the Great Dark Spot (GDS) is seen at the center.

It also allowed scientists to note the differences between Neptune's Dark Great Spots and Jupiter's Great Red Spot - a storm first observed in 1830 and that could be up to 350 years old.

These high-altitude white clouds, the team says, are made up of methane ice crystals. Scientists believe that these methane clouds accompany the storms that cause dark spots. And the United States space agency's eye in the sky has now unveiled two new incredible images, shot from 56 million light years distant. They can generally survive the planet's westward equatorial winds, and eastward-blowing currents close to the equator, before getting ripped apart in higher latitudes.

But, when Hubble attempted to take a look at the same features just five years later, in 1994, both of the massive storms were gone.

"We have never directly measured winds within Neptune's dark vortices, but we estimate the wind speeds are in the ballpark of 328 feet (100 meters) per second, quite similar to wind speeds within Jupiter's Great Red Spot", says Michael Wong, a planetary scientist at the University of California, Berkeley.

Andrew I. Hsu et al.

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