The Galileo spacecraft's measurements of Ganymede's magnetic field suggested there could be a subsurface layer of salt water, which unlike ice is a good conductor of electricity. Other instruments will characterise the plasma environment around the moon, studying the particles in it, and will investigate the outer layers of the moon's thin atmosphere. To do this, some of the mission's instruments will measure the moon's magnetic field, both its intrinsic component and that induced by Jupiter. This includes looking into how particles in the near-Ganymede space environment affect the composition of the moon's surface, how auroras develop on the satellite, and how Ganymede's magnetic field influences auroras on Jupiter. JUICE aims to study these interactions in detail. Ganymede's miniature magnetosphere lies within Jupiter's much larger magnetosphere, with complex interactions happening between the two. No other moon in the Solar System is known to have one, and only two other solid bodies (Mercury and the Earth) generate magnetic dipole fields. One of Ganymede's most remarkable features is its intrinsic magnetic field, discovered by the Galileo mission. This heat could drive some tectonic activity and provide one of the necessary conditions for life to emerge: a source of energy. Researchers believe there is tidal heating on Ganymede, although to a much smaller degree than on Io and Europa. It is the seventh moon from the gas giant (and the third among the Galilean satellites) and orbits Jupiter at a distance of more than 1 million kilometres. With a diameter of about 5260 km, larger than that of Pluto and Mercury, Ganymede tops the Solar-System moons' size chart. Ganymede is the primary scientific target of the mission. JUICE will study the three icy bodies-Europa, Ganymede and Callisto-to find out more about these potentially habitable environments. They contain more than 99% of the mass orbiting around Jupiter, are among the largest satellites in the Solar System, and have remarkable geologies. Scientists think that the crater may, in some unknown way, be responsible for the large region of cold temperatures that surrounds it.Out of Jupiter's nearly 70 moons, the four Galilean satellites-Io, Europa, Ganymede and Callisto-stand out as distinctive planetary worlds in their own right. The cold side includes the giant Herschel Crater, which is a few degrees warmer than its surroundings and so shows up in pink.
Scientists think the cold part is colder because some kind of unidentified surface material on Mimas is allowing the Sun's energy to soak into the subsurface of the moon instead of only warming the surface, but why the transfer of heat varies so dramatically is still a big mystery. Typical temperatures on the warm part are near 92 K (-294 F), and typical temperatures on the cold part are near 77 K (-320 F). Instead of the smoothly changing temperatures that we see on most moons, Mimas is divided into a warm part (in yellow), and a cold part (in purple), with a sharp V-shaped boundary between them. To study this, they took infrared images of the surface, giving them a heat map of the moon.
Astronomers were curious about the temperature patterns on the moon, and whether the crater would affect how Mimas is heated by the Sun. Looking at Mimas in visible light, there is a huge crater on the surface called Herschel crater. By splitting the light from Io using a spectrograph, astronomers were able to identify the molecular "fingerprints" of the sulfur and sulfur dioxide in the light.
#IO MOON DIAMETER IN KM PATCH#
A plume can be spotted in the upper right corner of the moon, in the same area as the bright hot patch in the infrared image to the lower right. Several of Io’s volcanoes produce plumes of sulfur and sulfur dioxide that climb as high as 500 km (300 mi) above the surface, and are easily seen in images like the one above. Infrared observations allow astronomers to easily pinpoint the volcanoes that are still active, allowing them to differentiate between current and old volcanic activity. Just as an elastic band warms up as you stretch it over and over again, the inside of Io heats up too, causing massive volcanic eruptions. Io's geologic activity is the result of “tidal heating” - the moon gets squeezed and stretched as it’s tugged around by the gravity of Jupiter and the other big moons, Europa, Ganymede, and Callisto.
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