Illustration of the internal structure of Io as revealed by Galileo. Underneath a low-density crust of 30-50 km thickness (grey outline) exists a global magma layer (asthenosphere) with a thickness exceeding 50 km and a rock melt fraction of a few tens of percent (red brown outline). The magnetic field of Jupiter is shown in blue lines.
Credit: Xianzhe Jia / University of Michigan, Ann Arbor
WASHINGTON: A re-analysis of data from NASA's Galileo spacecraft strengthens the theory that Jupiter's moon Io - the most volcanically active body in our solar system - has a magma ocean splashing around inside it.
Io produces 100 times more lava than Earth, and a new study in the current issue of Science has shed light on how that happens. A vast ocean of molten rock, known as magma, lies about 30-50 km under the Jupiter moon's crust.
"The blistering temperature of the magma ocean probably exceeds 1,200 degrees Celsius," NASA said.
Vast reservoir of magma
The volcanoes were first discovered in 1979 by NASA's Voyager spacecraft, and they are believed to draw energy from the "squeezing and stretching of the moon by Jupiter's gravity as Io orbits the immense planet", NASA said.
The extent of melting in the moon's interior has been a long-standing subject of debate, but lead author Krishan Khurana and colleagues from the University of California, Los Angeles, have taken a close look at the magnetometer data collected by Galileo, suggesting that the readings provide evidence for the presence of extensive melt.
The researchers exploited Jupiter's rotating magnetic field as a sounding signal and found that Io's inductive response to it suggests a vast, electrically conductive reservoir of magma beneath the moon's crust.
According to Khurana, the magma ocean is "millions of times better at conducting electricity than rocks typically found on the Earth's surface".
Magnetic field betrays its presence
"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," said Khurana.
"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."
In the absence of seismometers and other direct sensing devices, electromagnetic studies such as these seem to provide the best look at the thermal and compositional states of planetary interiors.
