Mysterious Shadowy Patches Baffle Scientists on Neptune

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In a spectacular revelation, astronomers have observed a vast, enigmatic dark spot on Neptune’s surface from Earth for the first time, accompanied by an intriguing bright counterpart in close proximity. This perplexing feature on the distant ice giant’s blue surface has piqued the interest of scientists worldwide, even as they grapple with the mystery of its origins. Utilizing the Very Large Telescope (VLT), researchers hope to glean insights into this puzzling Neptunian anomaly, first spotted by NASA’s Voyager 2 spacecraft in 1989.

The discovery of dark spots on planetary surfaces is not a new phenomenon for astronomers. However, the dark spot on Neptune has proven to be an anomaly, disappearing after Voyager 2’s observations, only for several new dark spots to be detected by the Hubble Space Telescope in 2018 across Neptune’s hemispheres. This development sparked the interest of Professor Patrick Irwin from the University of Oxford who, leading a team of researchers with the VLT’s Multi Unit Spectroscopic Explorer (MUSE), aimed to debunk the theory that these dark spots are a result of clearings in clouds over the ice giant’s frozen surface.

Observing Neptune’s Dark Spot from Earth: A New Discovery

Astronomers have recently spotted an enormous, enigmatic dark spot on the surface of Neptune from Earth for the first time, uncovering an equally baffling bright spot nearby. The origins of this shadowy patch on the blue surface of the distant ice giant are still unknown, but using the Very Large Telescope (VLT), scientists hope to unravel the mystery behind this Neptunian feature.

A Historical Perspective

The first dark spot on Neptune was observed by NASA’s Voyager 2 spacecraft in 1989 during its journey out of the solar system. Dark spots are not a new phenomenon; they have been observed on other planets since the 1800s, such as Jupiter’s "Great Red Spot". However, Neptune’s dark spot was peculiar as it vanished after Voyager 2’s observations. The intrigue deepened in 2018 when the Hubble Space Telescope detected several new dark spots on both the southern and northern hemispheres of Neptune.

Deep Dive into Neptune’s Dark Spots

Prompted by these observations, a team of researchers led by University of Oxford professor Patrick Irwin embarked on a mission to investigate Neptune using the VLT’s Multi Unit Spectroscopic Explorer (MUSE). This instrument focused on a spot in the planet’s northern hemisphere, which led researchers to dismiss the previously proposed explanation that dark spots were caused by clearings in clouds over the ice giant’s frozen surface.

In the words of Patrick Irwin, “Dark spots are very large, 6,200 to 9,300 miles (10,000 – 15,000 km) in diameter and very mysterious”. The team not only observed the dark spot from Earth but also detected a deep, bright spot, labeled DBS-2019, adjacent to the dark spot, a feature never seen before.

Unraveling the Mystery

The team utilized MUSE to measure reflected light from Neptune’s dusky patch and discovered that the spot isn’t darker due to cloud density, but because the atmospheric particles themselves are darker. These particles emit light at wavelengths of 700 nanometers, equivalent to the color red in the electromagnetic spectrum. The bright spot, located at the same atmospheric level as the dark spot, was absent in previous observations of Neptune, implying it is a short-lived feature.

The cause of the dark spots on Neptune is still unknown, but according to Irwin, there are a few plausible hypotheses. One suggests that the shadowy patches could result from the addition of darker particles from below. Alternatively, ultraviolet light may cause local heating, transforming hydrogen sulfide ice directly from a solid to a gas, thereby releasing a darker haze in the Neptunian atmosphere.

Looking Ahead

The ability to observe such features from Earth signifies a significant advancement in planetary astronomy. However, Irwin and his team plan to delve deeper into their research using the James Webb Space Telescope (JWST). As Irwin eagerly stated, "I can’t wait to get cracking on these data!"


This discovery opens up a new avenue for understanding Neptune’s atmospheric dynamics and the similar phenomena that might occur in other gas giants. The detection of such features from Earth itself is a testament to the progress in astronomical observation technologies. However, the mystery of Neptune’s dark spots indicates that our understanding of the universe is still riddled with enigmas, requiring continued exploration and scientific curiosity.

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