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Close flybys of Io, one of Jupiter’s moons and the most volcanically active world in our solar system, have revealed a lava lake and an imposing structure called “Beetle Mountain” on the moon’s alien surface.
NASA’s Juno spacecraft, which first arrived to study Jupiter and its moons in 2016, flew within approximately 930 miles (1,500 kilometers) of the lava world’s surface in December and February to capture the first detailed images of Io’s northern latitudes.
It’s been more than 20 years since a mission passed so close to Io, and the spacecraft’s camera, called JunoCam, captured high-resolution images that showed active volcanic plumes, mountain peaks and a smooth lake of cooled lava.
“Io is simply packed with volcanoes, and we captured some of them in action,” Scott Bolton, Juno principal investigator at the Southwest Research Institute, said in a statement.
“We also got great close-ups and other data from a 200-kilometer-long lava lake called Loki Patera. There are amazing details that show these crazy islands embedded in the middle of a potentially magma lake surrounded by hot lava,” she added. “The specular reflection that our instruments recorded in the lake suggests that parts of Io’s surface are as smooth as glass, reminiscent of obsidian glass created volcanically on Earth.”
Bolton announced the findings on April 16 in the General Assembly of the European Geophysical Union in Vienna. The new data paints a clearer picture of Io, which has intrigued scientists for centuries.
“Other than Earth, it is the only place where we see active magma volcanoes in our solar system,” Bolton said.
Animating an alien world
The team translated parts of Juno’s data into animations that bring some of the infernal world’s surface features, such as Loki Patera and Steeple Mountain, into dramatic focus.
Juno detected the mountain with the help of the sun shining on Io’s surface, which created dramatic shadows that revealed a very sharp peak.
“We use scientific data to understand shadows and measure distance,” Bolton said. “It might not be perfectly right, but it would be like that if you went there. We call it Steeple Mountain because it’s so steep at the edge that it could be Io’s version of the Matterhorn.”
Although the temperature of magma on Io reaches thousands of degrees, the moon’s surface is likely minus 148 degrees Fahrenheit (minus 100 degrees Celsius), Bolton said.
“When magma comes out when a volcano explodes, it immediately freezes and probably forms sulfurous snow,” he said.
As an outdoor enthusiast, Bolton joked that Io’s Steeple Mountain should be one of the solar system’s ski and snowboard destinations.
Meanwhile, Loki Patera is another location with extremes of heat and cold. While the lava lake itself is likely very hot, the tops of the islands are likely very cold, and a cold crust may also surround the edges of the lake, Bolton said.
The mission team used Juno’s Microwave Radiometer instrument to create maps of Io’s surface, showing how incredibly smooth it is.
The topography lacks contours because Io is so volcanically active that the world is constantly resurfaced by lava, which erases impact craters from its surface, according to a new study from a separate research team published in the journal Io. Science on April 18th.
The team also used the Atacama Large Millimeter/submillimeter Array of telescopes in Chile to observe gases in Io’s atmosphere. The researchers found evidence of an abundance of enriched sulfur and chlorine, which suggests that Io was likely volcanically active and releasing the gases for most or all of its history over the past 4 billion years.
Revealing the mysteries of Io
Io, first discovered by Galileo Galilei in 1610, is only slightly larger than our moon, but it is unlike anywhere else in the solar system.
The moon’s rocky surface is covered in hundreds of volcanoes, drawing comparisons to the fictional volcanic planet Mustafar and its rivers of lava from the “Star Wars” films.
Scientists have observed Io’s powerful volcanoes spewing fountains of lava tens of kilometers high that can even be seen with large telescopes on Earth, according to NASA.
The moon’s name came from a Greek myth in which a mortal woman is transformed into a cow during a marital dispute between the god Zeus and his wife Hera. The nickname is apt, because Io is in a constant state of tug-of-war, pulled by Jupiter’s enormous gravity, as well as its large moons Europa and Ganymede.
These three worlds pull on Io so violently that its surface juts in and out by 100 meters, like high and low tides on Earth – but this is happening on dry land, not in an ocean. Bolton said he often refers to Io as “Jupiter’s tortured moon” because of the fierce forces it regularly encounters.
The forces exerted on Io by Jupiter, Europa, and Ganymede cause Io’s surface to face an enormous amount of heat, which is why the moon’s subsurface remains as liquid rock. Researchers believe liquid rock is made from molten sulfur or silicate rock, and volcanic eruptions help the moon relieve gravitational pressure.
Io has been studied by multiple spacecraft, including the Pioneer and Voyager probes in the 1970s and the Galileo spacecraft in the 1990s. And now, Juno’s revelations are helping scientists understand the forces behind the Moon’s volcanic activity like never before.
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