Space and Physics
In a matter of years, we will be getting incredible new high-resolution images of Jupiter, in particular its icy moons, from the Jupiter Icy Moons Explorer (JUICE): the European Space Agency (ESA) mission that will study Europa, Ganymede, and Callisto. The road to Jupiter is still long, and to get a boost, it flew past Earth and the Moon. This was also a chance to test the scientific instruments.
The flyby was historic. Never before had a Lunar-Earth gravity assist been attempted – in fact, this was the first time a spacecraft attempted to fly by two celestial bodies in rapid succession to change its speed and direction. Passing by the Moon first was a perfect opportunity to see how the instruments will behave observing a body similar to the targets due to its extremely tenuous atmosphere.
ESA and the Italian Space Agency have now released the images collected by the JANUS camera, which will perform the actual scientific imaging once the mission reaches Jupiter. Based on Earth and Moon views alone, these are fantastic.
Once in the Jovian system, JANUS will do marvelous things. At its nearest approach, JANUS will map the clouds of Jupiter with a resolution of 10 kilometers (6.2 miles) per pixel. Once the mission enters orbit around Ganymede (the first spacecraft to ever orbit a moon other than our own), it will deliver a resolution of 2.4 meters (7.9 feet) per pixel. JANUS will deliver 50 times more coverage and precision than any previous camera sent to Jupiter.
The acronym JANUS comes from the Latin phrase "Jovis, Amorum ac Natorum Undique Scrutator" - "Scrutiniser of Jupiter, and all his loves and descendants". Jupiter’s moons are named after the descendants or lovers of Jupiter (or the counterpart in Greek mythology, Zeus).
Europa was a Phoenician princess kidnapped by Zeus in the form of a bull. She was the mother of King Minos of Crete – lots of bull-related stories around Minos. Then there’s Ganymede, a young man from Troy and the most handsome of all mortals. Zeus was so enamored by him that once again kidnapped him a made him a cup-bearer on Olympus.
Yes, a lot of kidnapping going on with Zeus – Callisto's tale is not a happy one of love and consent. A nymph follower of the goddess Artemis, she was tricked by Zeus into sleeping with him because he made himself look like Artemis. Once she fell pregnant, the trick was discovered and a furious Hera transformed her into a bear. Later on, when she was about to be killed by her son, she was set among the stars as Ursa Major, the constellation that includes the Big Dipper.
Beyond mythology, the reason to study these three icy moons (and get more insights into volcanic Io) is that they are believed to have deep oceans of water underneath a thick icy, or rocky and icy, exterior. Could the right conditions for life exist within these worlds? JUICE may find out.
JUICE is now en route to Venus. It will be using the planet for a gravity assist in August 2025. Then the spacecraft will come back towards Earth, flying by in September 2026 and a final flyby in January 2029. It is due to reach Jupiter and its icy moons in 2031.
4![An artist’s concept looks down into the core of the galaxy M87, which is just left of centre and appears as a large blue dot. A bright blue-white, narrow and linear jet of plasma transects the illustration from centre left to upper right. It begins at the source of the jet, the galaxy’s black hole, which is surrounded by a blue spiral of material. At lower right is a red giant star that is far from the black hole and close to the viewer. A bridge of glowing gas links the star to a smaller white dwarf star companion immediately to its left. Engorged with infalling hydrogen from the red giant star, the smaller star exploded in a blue-white flash, which looks like numerous diffraction spikes emitted in all directions. Thousands of stars are in the background.]](https://assets.iflscience.com/assets/articleNo/76155/aImg/79193/jet-m.jpg)
