(ORDO NEWS) — The gas giant has 79 known moons (and possibly even more unknowns), one of them even larger than Mercury. Juno explores connections between some of these moons and the planet—and sometimes, seeing them appear, photographs Jupiter itself.
The last of the shots is so breathtaking that it almost looks like a piece of science fiction. Jupiter appears large, with its classic bands of swirling clouds and patchy cyclones clearly visible in the southern hemisphere in sunlight.
To the right of the giant planet, two relatively small specks float serenely against the backdrop of inky darkness. These are two of the four Galilean satellites of Jupiter – the largest of its satellites, discovered by Galileo Galilei.
The two pictured here are the smaller of the four: Io, with an equatorial diameter of 3,643.2 km; and Europe with an equatorial diameter of 3121.6 km.
Each of these moons is an interesting target in itself to study. Io is the most volcanically active body in the solar system, with over 400 active volcanoes on its surface. This is the result of internal gravitational stresses created on the Moon not only by Jupiter, but also by three other Galilean satellites.
Volcanic activity leads to the fact that the atmosphere of Io is enriched with sulfur dioxide erupted by volcanoes. This atmosphere is constantly leaking out, forming a plasma torus around Jupiter itself, which is guided along the magnetic field lines and falls on Jupiter’s poles, creating permanent auroras.
The constant sulfur eruption has also covered Io itself with various sulfur compounds that give the moon a predominantly yellow tint.
Meanwhile, Europa is an object of interest in the search for life beyond Earth. Beneath its pale icy shell lies an inner liquid ocean. Although the Moon is far from the Sun, it too can be internally heated by gravitational stress.
If so, there may be hydrothermal vents at the bottom of its global sea. Here on Earth, holes like this are a haven for food webs that rely not on photosynthesis but on chemosynthesis to survive: using chemical reactions to get food.
This led astrobiologists to believe that, of all the worlds in the solar system, icy moons such as Europa and Saturn’s moon Enceladus might be the most likely places to find extraterrestrial life.
Juno will make a close flyby of these two very different worlds.
The probe will visit Europe, which is also the target of a special mission planned for 2024, this September. Meanwhile, flights over Io are scheduled for late 2023 and early 2024.
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