In this stunning image, Jupiter’s colorful clouds are interrupted by the orange-colored moon Io, which casts a shadow toward the planet’s western edge. Hubble’s amazing resolution allows us to observe Io’s mottled-orange surface, attributed to its abundant active volcanoes. These fiery wonders were first revealed during the Voyager 1 flyby in 1979. Beneath its thin crust, Io’s interior seethes with molten material periodically ejected through volcanoes. The diverse color palette of Io’s surface comes from sulfur reacting to different temperatures, resulting in a fascinating display. Credit: Science: NASA, ESA, STScI, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley), Image Processing: Joseph DePasquale (STScI)
Forecast for Blustery Winds, Smoggy Hazes
The outer planets beyond[{” attribute=””>Mars do not have solid surfaces to affect weather as on Earth. And, sunlight is much less able to drive atmospheric circulation. Nevertheless, these are ever-changing worlds. And Hubble – as interplanetary meteorologist – is keeping track, as it does every year. Jupiter’s weather is driven from inside-out as more heat percolates up from its interior than it receives from the Sun. This heat indirectly drives color change cycles highlighting a system of alternating cyclones and anticyclones. Uranus has seasons that pass by at a snail’s pace because it takes 84 years to complete one orbit about the Sun. The seasons are extreme because Uranus is tipped on its side. As summer approaches in the northern hemisphere, Hubble sees a growing polar cap of high-altitude photochemical haze that looks similar to the smog over cities on Earth.
Hubble Monitors Changing Weather and Seasons at Jupiter and Uranus
Ever since its launch in 1990, NASA’s Hubble Space Telescope has been an interplanetary weather observer, keeping an eye on the largely gaseous outer planets and their ever-changing atmospheres. NASA spacecraft missions to the outer planets have given us a close-up look at these atmospheres, but Hubble’s sharpness and sensitivity keeps an unblinking eye on a kaleidoscope of complex activities over time. In this way Hubble complements observations from other spacecraft such as Juno, currently orbiting Jupiter; the retired Cassini mission to Saturn, and the Voyager 1 and 2 probes, which collectively flew by all four giant planets between 1979 and 1989.
Inaugurated in 2014, the telescope’s Outer Planet Atmospheres Legacy (OPAL) Program has been providing us with yearly views of the giant planets. Here are some recent images:
Hubble Space Telescope images of Jupiter taken on November 12, 2022 (left) and January 6, 2023 (right). Credit: Science: NASA, ESA, STScI, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley), Image Processing: Joseph DePasquale (STScI)
Jupiter
[left]—The forecast for Jupiter is stormy weather in low northern latitudes. A prominent string of alternating storms is visible, forming what some planetary astronomers call a “vortex street”. It is a wave pattern of nested anticyclones and cyclones, locked together as in a machine with alternating gears moving clockwise and counterclockwise. If the storms were close enough to each other, in the unlikely event of a merger, they could form a larger storm, potentially rivaling the current size of the Great Red Spot. The staggered pattern of anticyclones and cyclones prevents individual storms from merging. Activity can also be seen within these storms; in the 1990s Hubble found no cyclones or anticyclones with built-in thunderstorms, but these storms have sprung up in the last decade. The stark color difference indicates that Hubble is also seeing different cloud heights and depths.
The orange moon Io photobombs this view of Jupiter’s multicolored cloud tops, casting a shadow toward the planet’s western side. Hubble’s resolution is so sharp that it can see Io’s mottled-orange appearance, associated with its many active volcanoes. These volcanoes were first discovered when the Voyager 1 spacecraft flew by in 1979. The moon’s molten interior is covered by a thin crust from which volcanoes spew material. Sulfur has different colors at different temperatures, which is why Io’s surface is so colorful. This photo was taken on November 12, 2022.
[right]—Jupiter’s legendary Great Red Spot is in the center of this view. Although this vortex is large enough to swallow the Earth, it has actually shrunk to the smallest size it has reached in observational records dating back 150 years. Jupiter’s icy moon Ganymede can be seen moving past the giant planet in the lower right. Slightly larger than the planet Mercury, Ganymede is the largest moon in the solar system. It is a cratered world with a primarily water-ice surface with apparent glacial flows caused by internal heat. (This photo is smaller in size because Jupiter was 81,000 miles away from Earth when the photo was taken). This photo was taken on January 6, 2023.
Hubble Space Telescope images of Uranus taken on November 9, 2014 (left) and November 9, 2022. Credit: Science: NASA, ESA, STScI, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley) , Image Processing : Joseph DePasquale (STScI)
Uranus
The planetary oddball Uranus rolls on its side around the Sun as it follows an 84-year orbit, rather than spinning in a more vertical position like Earth does. Uranus has a peculiarly tipped “horizontal” rotation axis that is only eight degrees from the plane of the planet’s orbit. A recent theory suggests that Uranus once had a massive moon that gravitationally destabilized it and then crashed into it. Other possibilities include giant impacts during planet formation, or even giant planets that exert resonant torques on each other over time. The consequences of the planet’s tilt are that for stretches of time lasting up to 42 years, parts of one hemisphere are completely without sunlight. When the Voyager 2 spacecraft visited in the 1980s, the planet’s south pole was almost directly pointed at the Sun. Hubble’s latest view shows the north pole now tilting toward the Sun.
[left]—This is a Hubble view of Uranus taken in 2014, seven years after the northern spring equinox when the Sun shines directly over the planet’s equator, and shows one of the first images from the OPAL program. Many storms appear with methane ice-crystal clouds in the mid-northern latitudes above the planet’s cyan-tinted lower atmosphere. Hubble photographed the edge-on ring system in 2007, but the rings are seen starting to open seven years later in this view. At this time, the planet had many small storms and even some wispy clouds.
[right]—As seen in 2022, the north pole of Uranus shows a thick photochemical haze that looks like smog in cities. Many small storms can be seen near the edge of the polar haze boundary. Hubble monitors the size and brightness of the north polar cap and it continues to brighten every year. Astronomers posit many effects—from atmospheric circulation, particle properties, and chemical processes—that control how the atmospheric polar cap changes with the seasons. At the Uranian equinox in 2007, neither pole was particularly bright. As the northern summer solstice approaches in 2028, the cap may get even stronger, and focus directly on Earth, allowing great views of the rings and north pole; the ring system appears in front. This photo was taken on November 9, 2022.
About Hubble
The Hubble Space Telescope represents a remarkable collaboration between NASA and ESA, with NASA’s Goddard Space Flight Center in Greenbelt, Maryland overseeing its management. Investigating the mysteries of the cosmos, the Space Telescope Science Institute (STScI) in Baltimore spearheaded Hubble’s scientific efforts. The Association of Universities for Research in Astronomy, located in Washington, DC, operates STScI on behalf of NASA.
