Galileo reveals magma ‘ocean’ under surface of Jupiter’s moon

New analysis from NASA’s Galeileo spacecraft shows that there is an ocean of molten (or partially molten magma) beneath the surface of Io, one of Jupiter’s moons. The finding was published today, May 13, in Science magazine.

Volcanic Io

Io is the most active volcanic object in our solar system, and this confirmation of a magma existing beneath its surface is the first explanation of this phenomena.

“The hot magma in Io’s ocean is millions of times better at conducting electricity than rocks typically found on the Earth’s surface,” said the study’s lead author, Krishan Khurana, a former co-investigator on Galileo’s magnetometer team and a research geophysicist with UCLA’s Institute of Geophysics and Planetary Physics. “Just like the waves beamed from an airport metal detector bounce off metallic coins in your pocket, betraying their presence to the detector, Jupiter’s rotating magnetic field continually bounces off the molten rocks in Io’s interior. The bounced signal can be detected by a magnetometer on a passing spacecraft”.

A magnetometer is an instrument used to detect the strength and direction of a magnetic field. The thing is, Earth’s internal core is made out of solid iron and nickel, due to the enormous pressure existing there. Such pressure, however, is believed to be impossible on Io, so this only leaves out a viscous or totally molten ocean of magma.

“Scientists are excited that we finally understand where Io’s magma is coming from and have an explanation for some of the mysterious signatures we saw in some of Galileo’s magnetic field data,” Khurana added. “It turns out Io was continually giving off a ‘sounding signal’ in Jupiter’s rotating magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface.”

Understanding volcanic phenomena

From what we know so far, Io is the only object aside from Earth that has active magma volcanoes, and man are they active ! Io erupts every year about 100 times more than all the active volcanoes on our planet combined, and while the volcanoes here are located mostly on the boundary of tectonic plates, volcanoes on Io are distributed evenly on the moon’s surface. This would seem to indicate the lack of tectonic plates on Io, but does indeed confirm the idea of a magma ocean beneath the surface.

“It has been suggested that both the Earth and moon may have had similar magma oceans billions of years ago, at the time of their formation, but they have long since cooled,” said Torrence Johnson, who was Galileo’s project scientist, based at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and who was not directly involved in the study. “Io’s volcanism informs us how volcanoes work and provides a window in time to styles of volcanic activity that may have occurred on the Earth and moon during their earliest history.”

Hot and cold

Io is one Jupiter’s moons, and it’s far enough from the Sun for everything down there to be frozen; however, Io’s volcanic activity has been proven since 1979, and since then several hotspots have been observed, with temperatures of 1300 – 1600 degrees (it is still a matter of debate).

The energy for this activity comes from Jupiter’s gravity, which pulls as the moon rotates around our solar system’s biggest planet, and researchers have known this for a long time, but they hadn’t been able to fit in the magnetic and gravitational data

“But at the time, models of the interaction between Io and Jupiter’s immense magnetic field, which bathes the moon in charged particles, were not yet sophisticated enough for us to understand what was going on in Io’s interior,” said study co-author Xianzhe Jia of the University of Michigan”

Relatively recent work has shown that ultramafic rocks (or ultrabasic), the ones who are on oceanfloors and in the mantle, can carry significant amounts of electrical currents when molten, and it was this research that pointed Khurana and his colleagues towards this study. Tests showed that the signatures detected by Galileo were consistent with a rock like lherzolite, an igneous rock rich in silicates of magnesium and iron found, for example, in Spitzbergen, Norway.

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