Astronomers just made an extremely detailed map of the solar system's most volcanically active body, Jupiter's moon Io, thanks to a rare orbital alignment.
Jupiter's third largest moon, Io sees at least six full-on volcanic explosions every day from among its hundreds of active volcanoes. The moon's lava flows often extend more than 300 miles. The moon's volcanism has been an object of wonder and curiosity since 1979, when Voyager 2 discovered the phenomena.
Good fortune struck on March 8, 2015, when another of Jupiter's moons, Europa, passed in front of Io, blocking out light from the volcanic moon. Europa's surface is covered in water ice, meaning that it reflects only a tiny amount sunlight at infrared wavelengths. That moment was just what astronomers at UC Berkeley needed to map out the heat coming from volcanoes on Io's surface, using the based out of Arizona to do so.
They paid particular attention to Loki Patera, a volcanic depression 126 miles long named after the Norse trickster god, which is essentially a sea of lava."If Loki Patera is a sea of lava, it encompasses an area more than a million times that of a typical lava lake on Earth," Katherine de Kleer, a UC Berkeley graduate student and the study's lead author. "In this scenario, portions of cool crust sink, exposing the incandescent magma underneath and causing a brightening in the infrared."
Europa covered Loki Patera for a full ten seconds, and there was "so much infrared light available that we could slice the observations into one-eighth-second intervals during which the edge of Europa advanced only a few kilometers across Io's surface," co-author Michael Skrutskie, of the University of Virginia, who led the development of the infrared camera used for this study. The wealth of data within those ten seconds allowed the astronomers to create a two-dimensional thermal map of Loki Patera with a resolution ten times sharper than would be possible otherwise.
Katherine de Kleer and her team also determined how recently new magma had been exposed at the surface of Loki, a process called overturn. There's a solid volcanic island in the middle of Loki, which, it turns out, is a dividing line: the eastern and western sides of the sea expose new magma to the surface at different speeds. It takes around 75 days on the eastern and in between 180 and 230 days on the western end.
"The velocity of overturn is also different on the two sides of the island, which may have something to do with the composition of the magma or the amount of dissolved gas in bubbles in the magma," de Kleer . "There must be differences in the magma supply to the two halves of the patera, and whatever is triggering the start of overturn manages to trigger both halves at nearly the same time but not exactly. These results give us a glimpse into the complex plumbing system under Loki Patera."
The moons of Jupiter have been of interest in recent years, with Europa emerging as one of the best candidates for life outside of Earth. If mankind ever gets there, it will also provide a great chance to look at Loki Patera up-close. As it stands, de Kleer, Skrutskie and other stargazers will have to wait until the next alingment between the two moons, which should come in 2021.