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How Astronomers Imaged an Alien Lava Lake From Earth

The Large Binocular Telescope Observatory provides the first detailed glimpse of the Loki Patera from Earth.
Io surface map. Image: NASA/Galileo/Voyager

In 1610, Galileo Galilei became the first person to glimpse the four largest moons of Jupiter, using a single lens refracting telescope—one of the most basic tools in astronomy.

Now, over 400 years later, a team of astronomers has used the sophisticated Large Binocular Telescope Observatory (LBTO) to zoom in on the fiery moon Io with a level of resolution never before achieved by a ground telescope.


Where Galileo was only able to make out the faint shape of Io and its siblings, the LBTO team has captured one of the moon's most iconic features—a tempestuous lava lake named the Loki Patera after the Norse god—in unprecedented detail. The researchers, led by LBTO astronomer Al Conrad, published their results this week in The Astronomical Journal.

The LBT image of Loki Patera (orange) laid over a Voyager image of the volcanic depression. Image: LBTO-NASA.

"While we have seen bright emissions […] 'pop up' at different locations in Loki Patera over the years, these exquisite images from the [Large Binocular Telescope Interferometer] show, for the first time in ground-based images, that emissions arise simultaneously from different sites in Loki Patera," said co-author Imke de Pater, an astronomy professor at Berkeley, in a statement.

"This strongly suggests that the horseshoe-shaped feature is most likely an active overturning lava lake, as hypothesized in the past," she added.

This glowing reservoir of molten lava is Io's largest volcanic depression, and stretches over 202 kilometers across the moon's tortured surface. It is far from the only lava lake to grace Io's surface, and dozens of other magma-rich pateras are sprinkled across the moon's surface.

Indeed, Io is by far the most geologically active world in our solar system, and is pockmarked with hundreds of active volcanoes and lava flows. This is a result of its position as the innermost moon of Jupiter, which constantly stretches and squeezes the small world with its colossal tidal forces, causing endless eruptions around the planet.


Comparison between a simulated view of Io through an 8-meter telescope (left) and the final real LBTI reconstruction (right). Credit: LBTO.

What's more, the LBTO team confirmed that the Loki Patera is itself prone to volcanic outbursts, which significantly boost its thermal emissions. Much like the film that forms on the top of a pudding, the lake is often topped by a thin crust of solid lava. When this crust reaches a certain weight, it sinks into the liquid magma, setting off all kinds of magmatic fireworks.

"Two of the volcanic features are at newly active locations," said co-author Katherine de Kleer. "They are located in a region called the Colchis Regio, where an enormous eruption took place just a few months earlier, and may represent the aftermath of that eruption."

"The high resolution of the LBTI allows us to resolve the residual activity in this region into specific active sites, which could be lava flows or nearby eruptions," she said.

True to its divine namesake, the Loki Pandera is the very picture of an impassioned firebrand. With the help of new super-powerful new telescopes like LBTO, astronomers can study this spectacular extraterrestrial lake of fire in increasingly stunning detail, despite the 600 million kilometers separating it from Earth.

Galileo would be proud.