What’s That Big White Splotch on Uranus?

What’s That Big White Splotch on Uranus?

With all the fanfare around the Webb Space Telescope, it’s easy to forget about the tireless work of Hubble, its predecessor. The 30-year-old orbiting observatory has taken new images of Jupiter and Uranus that reveal recent changes in the atmospheres of the two worlds.

Jupiter and Uranus are the fifth and seventh planets from the Sun, respectively. The milky-orange gas giant Jupiter is the largest planet; 11 Earths could fit across its equator, while Uranus — a dusty blue — is just about four times wider than Earth.

In these Uranus images, taken in November 2014 and November 2022, we can see intriguing atmospheric activity on the planet. In the 2014 image, ice-crystal clouds composed of methane sit toward the north, and a ring system is faintly visible around the aquamarine marble.

In the 2022 view, Uranus’ rotational axis is severely off-kilter, causing the planet’s north pole to be turned toward the Sun. That pole is dominated by a polar cap, and a few storms are visible on its perimetre. By 2028, the polar ice cap will be turned directly toward Earth, giving telescopes like Hubble a great opportunity to better image the structure.

Jupiter’s atmosphere is famously turbid: Its Great Red Spot is a gigantic storm system that has persisted for at least centuries, but the entire planet can be characterised by swirling cyclones. Unsurprisingly, according to Hubble’s observations, Jupiter’s weather forecast is stormy, especially at the lower latitudes.

What’s That Big White Splotch on Uranus?

The stormy weather on the gas giant is clear to see in images taken by Hubble in November 2022 and January 2023. In the first, a series of storm systems known as a “vortex street” is visible in the wavelike pattern of clouds. This is a system of cyclones and anticyclones abutting one another. Due to the opposite rotation of each adjacent system, individual storms cannot merge. At centre, Jupiter’s moon Io is visible, as is Io’s shadow to the left.

The second image shows the Great Red Spot and the moon Ganymede, toward the bottom-right of the planet. Ganymede is soon to be explored by the European Space Agency’s Jupiter Icy Moons Explorer (or JUICE) mission.

Hubble launched in 1990; since then, the telescope has imaged galaxy mergers, measured the mass of distant stars, and even studied other NASA missions, like the DART spacecraft’s collision with an asteroid back in September.

It’s had stumbles along the way. The telescope has needed several reboots in recent years as its ageing software has stuttered, and it has even been manually serviced in space five times. But the intrepid observatory keeps on going, now working in tandem with its successor, Webb.

More: Satellite Swarms Like SpaceX’s Starlink Are Increasingly Spoiling Hubble Telescope Images

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