The usual icy blue tone of Neptune was disrupted by a brewing storm in a new photograph taken by the Hubble Space Telescope.

Dark Spot In Neptune's Pristine Blue Atmosphere

During last year's routine monitoring of the outer planets of the solar system, NASA spotted a "mysterious dark vortex" in the atmosphere of the ice giant. It is located in the northern hemisphere of Neptune and measures about 11,000 kilometers across.

This, however, is not something that has never been seen before. The feature is the fourth "mysterious dark vortex" captured by the Hubble Space Telescope since 1993. The Voyager 2 spacecraft also discovered two other spots when it flew by the planet in 1989.

According to NASA, the "mysterious dark vortex" is a storm that is a result of the ice giant's southern summer. Scientists do not really know how storms in Neptune form, but a previous study led by the University of California, Berkeley estimates that they appear every four to six years and disappear after two years.

The photograph above was captured by the Hubble Space Telescope in September. It also shows "companion clouds" that appear along with the vortices.

Scientists believe that the dark vortex in Neptune behaves similarly to the infamous Great Red Spot in Jupiter; the storm swirls, pulling up dark material from deeper in the atmosphere. NASA noted that prior to the appearance of the storm, increased cloud activity in the area was observed beginning in 2016.

Observing Neptune is not an easy task. The ice giant is the eighth and farthest planet from the sun and is approximately 4.4 billion kilometers away from Earth. So far, no other facilities aside from Hubble and Voyage have observed the planet's vortices.

Uranus' New White Cap

Last year, the Hubble Space Telescope also captured a new feature on Neptune's neighbor, Uranus. The giant is sporting a wide white spot across its north pole.

NASA explained that the planet is in the middle of summer and because of its weird tilt, the north pole is always facing the sun, never setting. The "cloud cap" may have formed as a result of the seasonal changes in the atmosphere.

At the edge of the storm is a compact methane-ice cloud. At the equator is another narrow cloud that encircles the planet.

Like Neptune, Uranus is extremely far away. At its closest, it is 2.6 billion kilometers away from Earth.

During its routine yearly monitoring of the weather on our solar system's outer planets, Hubble uncovered a new mysterious dark storm on Neptune and provided a fresh look at a long-lived storm circling around the north polar region on Uranus: https://t.co/ErZTfFwZfF pic.twitter.com/NzHhhxOK8n — Hubble (@NASAHubble) February 7, 2019