NASA's Hubble captures seasonal changes on Saturn while Juno snaps Jupiter's moon Ganymede for the first time
Hubble photographed a slight reddish haze over Saturn's northern hemisphere and this may be due to heating from increased sunlight while the south pole has a blue hue
Summer in Saturn and the first pictures of the northern frontier of Jupiter’s moon Ganymede, the ninth-largest object in the solar system, are two stunning images captured by NASA's Hubble and Juno respectively.
It is summer on Saturn’s northern hemisphere and NASA's Hubble Space Telescope snapped this on July 4, 2020, when the planet was 839M miles from Earth. The new Saturn image shows that the rings are mostly made of pieces of ice, with sizes ranging from tiny grains to giant boulders. Just how and when the rings formed remains one of the solar system's biggest mysteries. Two of Saturn's icy moons are clearly visible in the image: Mimas at right and Enceladus at the bottom.
Hubble photographed a slight reddish haze over the northern hemisphere. According to scientists, this may be due to heating from increased sunlight, which could either change the atmospheric circulation or perhaps remove ices from aerosols in the atmosphere. Another theory is that the increased sunlight in the summer months is changing the amounts of photochemical haze produced. Conversely, the south pole has a blue hue, reflecting changes in Saturn's winter hemisphere. “It's amazing that even over a few years, we're seeing seasonal changes on Saturn," says lead investigator Amy Simon of NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a statement.
The image was taken as part of the Outer Planets Atmospheres Legacy (OPAL) project. It is helping scientists understand the atmospheric dynamics and evolution of the solar system's gas giant planets. In Saturn's case, astronomers continue tracking shifting weather patterns and storms.
Hubble also found several small atmospheric storms. "These are transient features that appear to come and go with each yearly Hubble observation. The banding in the northern hemisphere remains pronounced as seen in Hubble's 2019 observations, with several bands slightly changing color from year to year. The ringed planet's atmosphere is mostly hydrogen and helium with traces of ammonia, methane, water vapor, and hydrocarbons that give it a yellowish-brown color," says NASA.
First images of Ganymede
Jupiter has a lot of moons but Ganymede, the biggest Jovian moon, is larger than both Mercury and Pluto. It is also the only moon in the solar system with its own magnetic field. And for the first time, NASA's Juno spacecraft has imaged the north pole of Ganymede. The images taken by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard Juno provide the first infrared mapping of Ganymede's northern frontier. Frozen water molecules detected at both poles have no appreciable order to their arrangement and a different infrared signature than ice at the equator.
"On its way inbound for a December 26, 2019, flyby of Jupiter, NASA's Juno spacecraft flew in the proximity of the north pole of the ninth-largest object in the solar system, the moon Ganymede. The infrared imagery collected by the spacecraft's JIRAM instrument provides the first infrared mapping of the massive moon's northern frontier," says NASA.
Ganymede consists primarily of water ice and its composition contains fundamental clues for understanding the evolution of the 79 Jovian moons from the time of their formation to today. "On Earth, the magnetic field provides a pathway for plasma (charged particles from the Sun) to enter our atmosphere and create aurora. As Ganymede has no atmosphere to impede their progress, the surface at its poles is constantly being bombarded by plasma from Jupiter's gigantic magnetosphere. The bombardment has a dramatic effect on Ganymede's ice," explain scientists.
JIRAM was designed to capture the infrared light emerging from deep inside Jupiter, probing the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter's cloud tops. But the instrument can also be used to study the moons Europa, Io, Ganymede and Callisto. "The JIRAM data show the ice at and surrounding Ganymede's north pole has been modified by the precipitation of plasma. It is a phenomenon that we have been able to learn about for the first time with Juno because we are able to see the north pole in its entirety," according to Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome.
The analysis reveals that the ice near both poles of the moon is 'amorphous' and researchers believe that the constant bombardment of charged particles onto the polar regions prevents the ice from forming a crystalline structure. "Charged particles follow the moon's magnetic field lines to the poles, where they impact, wreaking havoc on the ice there, preventing it from having an ordered (or crystalline) structure. Frozen water molecules detected at both poles have no appreciable order to their arrangement, and the amorphous ice has a different infrared signature than the crystalline ice found at Ganymede's equator," says NASA.