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Dark Storm on Neptune Reverses Direction, Possibly Shedding a Fragment


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When NASA's Voyager 2 spacecraft flew by Neptune in 1989 after a nearly 3-billion-mile odyssey, astronomers expected to get a close-up look at a blue-green planet that seemed as featureless as a marble. Instead, they were shocked and intrigued to see a dynamic and turbulent world of whirling storms, including a giant feature dubbed the Great Dark Spot, looming in Neptune's far southern hemisphere.

The vortex was reminiscent of Jupiter's legendary Great Red Spot, a monstrous storm that has been raging for hundreds of years. Had this Great Dark Spot been brewing for the same amount of time? Or, was it a more ephemeral tempest?

Scientists had to wait until 1994, when the Hubble Space Telescope and its crisp vision peered at distant Neptune. The mysterious spot had vanished! This game of planetary peek-a-boo continued when Hubble spotted another dark storm appearing in Neptune's northern hemisphere in 1995. Over the past three decades, Hubble has continued to observe the planet, watching several more dark spots come and go.

Only Hubble can study these spots because it has the sharp vision to observe them in visible light. Hubble has shown that these storms live for a few years before vanishing or fading away.

Researchers thought the current giant storm in the northern hemisphere was heading to destruction when it mysteriously halted its southern journey and began drifting northward. At the same time as the spot's stunning reversal, a new, slightly smaller dark feature appeared near its bigger cousin and later disappeared. These surprising events add to the mystery of this dynamic world.

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      Researchers from the University of Bergen in Norway led the study in collaboration with scientists from NASA’s Marshall Space Flight Center in Huntsville, Alabama, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the U.S. Naval Research Laboratory, and multiple universities in the U.S., Mexico, Colombia, and Europe. The findings were described in a pair of papers in Nature, published Oct. 2.
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      NASA’s high-flying ER-2 airplane carries instrumentation in this artist’s impression of the ALOFT mission to record gamma rays (colored purple for illustration) from thunderclouds.Credit: NASA/ALOFT team The researchers had hoped ALOFT instruments would observe fast radiation bursts known as terrestrial gamma-ray flashes (TGFs). The flashes, first discovered in 1992 by NASA’s Compton Gamma Ray Observatory spacecraft, accompany some lightning strikes and last only millionths of a second. Despite their high intensity and their association with visible lightning, few TGFs have been spotted during previous aircraft-based studies.  
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      Turning to aircraft-based instrumentation rather than satellites ensured a lot of bang for research bucks, said the study’s project scientist, Timothy Lang of NASA’s Marshall Space Flight Center in Huntsville, Alabama. 
      “If we had gotten one flash, we would have been ecstatic — and we got well over 100,” he said. This research could lead to a significant advance in our understanding of thunderstorms and radiation from thunderstorms. “It shows that if you have the right problem and you’re willing to take a little bit of risk, you can have a huge payoff.”
      By James Riordon
      NASA’s Earth Science News Team
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      Last Updated Oct 02, 2024 EditorJenny MarderContactJames RiordonLocationMarshall Space Flight Center Related Terms
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