Icy Europa Does Battle With Solar System's Most Hellish Moon

The astronomical juxtaposition couldn’t be any more stark: in the series of observations above, Jupiter’s icy moon Europa passes in front of Io, fellow Jovian moon, but also the most volcanically active place in the entire solar system.

Imaged by the huge Large Binocular Telescope (LBT), located in the Pinaleno Mountains, Ariz., this Jovian occultation on March 7 serves as a reminder as to the complex assortment of moons our solar system possesses.

On the one hand, we have an ice-encrusted Europa that has a sub-surface ocean with huge habitable potential for exo-marine life. But on the other, there’s a magma-covered Io convulsing with powerful volcanic eruptions. Though their differences are obvious, Europa’s habitable potential and Io’s volcanoes are driven by the same force: the tides of Jupiter.

As the closest Galilean moon in the Jupiter system with an eccentric orbit, Io bears the brunt of Jupiter’s tides, suffering huge tidal stresses as it travels around the massive gas giant. This creates an internal dynamo that keeps the 1,942 mile (3,636 kilometer) wide moon in a constantly-erupting state — the stress often becomes too great and huge explosions eject magma from the splitting crust. Orbiting further away, Europa (that is slightly smaller than Io with a diameter of 1,950 miles) also feels these tides, but the impact is far less dramatic.

Below the thick ice crust is an ocean that is kept in a liquid state by Jupiter’s tides compressing Europa’s core. But rather than generating the pressure-cooker that is Io, Europa has an internal heater that generates enough heat to keep its underground ocean liquid.

Loki, the Fire God

Now, by using the LBT’s twin 8.4 meter (27 feet) telescopes working in unison, never before seen features on Io’s surface pop into view.

A pooling, vast lake of magma is known to exist on Io, covering a region 124 miles wide. This feature, called “Loki” after the Norse god of fire and chaos, is known as a patera where a cooling lava crust floats atop molten rock. Periodically, the upper layers submerge into the magma, generating a surge in thermal emissions that can be observed from Earth.

Observing Io with the Large Binocular Telescope Interferometer, or LBTI, in infrared light, features in the Loki Patera have become easier to study.

“We combine the light from two very large mirrors coherently so that they become a single, extremely large mirror,” said Al Conrad, scientist at the Large Binocular Telescope Observatory, and lead author of the study published in the Astrophysical Journal. “In this way, for the first time we can measure the brightness coming from different regions within the lake.”

“While we have seen bright emissions — always one unresolved spot — ‘pop up’ at different locations in Loki Patera over the years,” added Imke de Pater, of the University of California, Berkeley, “these exquisite images from the LBTI show for the first time in ground-based images that emissions arise simultaneously from different sites in Loki Patera. This strongly suggests that the horseshoe-shaped feature is most likely an active overturning lava lake, as hypothesized in the past.”

“Two of the volcanic features are at newly active locations,” said Katherine de Kleer, also from the University of California, Berkeley. “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.”

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