Planets

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.

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.

ANALYSIS: Jupiter Moon Io Unleashes Cataclysmic Eruptions

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.

ANALYSIS: Tidal Heating Could Kill ‘Habitable' Alien Worlds

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.

NEWS: Volcanoes on Jupiter's Moon Io Are All Wrong

"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."

ANALYSIS: See 3 Moons of Jupiter Perform Rare Triple Transit

When powerful telescopes like the LBT turn their attentions to individual moons, we begin to learn new things about their nature and how they formed, creating an understanding as to the history of our solar system. And as we watch the erupting Io under constant tidal torture pass behind the serene Europa, it's a timely reminder of this wonderful diversity.

For more information about the LBT and how these detailed observations of Io are achieved, see the University of Arizona press release.

The March 7 occultation of Io by its neighboring moon Europa as observed by the Large Binocular Telescope. Loki is the bright volcano on the left and Pele the other one on the lower right. Europa appears dark because the water ice on its surface absorbs the incident sunlight at the wavelength used.

On August 4, the much-anticipated "Wonders of the Solar System" documentary will premier on the Science Channel.

Presenter and physicist Prof. Brian Cox will show you the hidden mysteries of our interplanetary neighborhood, as well as breathtaking sights of the planets, moons and the sun. Cox will also examine some of Earth's extreme environments to see how life has adapted, perhaps helping us understand whether life can exist elsewhere in our solar system. To provide a taster of what you can expect from "Wonders," Discovery News has gathered some facts, figures and the best images of our solar system to assemble a special Wide Angle supporting this groundbreaking documentary. Let's begin, in the orbit of the solar system's biggest planet, Jupiter...

Moons of Jupiter: Io

Welcome to Jupiter, the solar system's biggest planet and host to more than 63 peculiar moons -- a steady contender for moons compared to satellite-strewn Saturn. From sulfur-spewing furnaces to ice-encrusted oceans, these Jovian satellites are anything but normal! Browse through 10 of our favorites here. If you're looking for a fiery, volcanic spectacle, head to Io, the innermost of Jupiter's "big four" moons. Jupiter's gravity pulls at Io so strongly that the land has tides of up to 300 feet (100 meters). This gravitational tug-of-war produces scorching heat and raises more volcanic activity here than anywhere else in the solar system. Io has a sulfurous surface, and its volcanoes spew silicate magma, causing the hellish moon's surface look like a pizza.

Moons of Jupiter: Metis

While it doesn't look like much in this image (the highest-resolution available!), Metis is Jupiter's closest companion -- for now. It's orbiting the gas giant at a distance of just 75,500 miles (128,000 kilometers) and moving faster than Jupiter spins. Metis is so close to Jupiter's surface, in fact, that it will gradually succumb to the planet's gravity and plunge into its churning clouds. This same principle applies to man-made satellites orbiting the Earth; if their orbit is too low, they'll eventually fall.

Moons of Jupiter: Adrastea

Like Metis, Adrastea is on its way down, eventually: Its orbit is just 1,000 kilometers (621 miles) outside of its fellow doomed moon. The two bodies probably provide lots of the material making up Jupiter's main ring, shown in this Galileo spacecraft image. Adrastea is also tiny at a wee 12 miles (20 kilometers) in diameter.

Moons of Jupiter: Ganymede

If Ganymede orbited the sun instead of Jupiter, it would be a planet of its own -- it's even bigger than Mercury. Its interior is made from layers surrounding a rocky core, and its surface is covered in water ice. Although Ganymede doesn't have much of an atmosphere, it does have some ozone gas near its surface. This gas comes from charged particles in Jupiter's magnetic field smacking into the moon's icy crust.

Moons of Jupiter: Themisto

We're not entirely sure what Themisto looks like, but scientists know it one odd little satellite. Unlike most other moons, Themisto is oblong and doesn't fit into the traditional groups of Jovian moons. Because this body is so small -- just 5 miles (8 kilometers) in diameter -- astronomers in 2000 confused it for a new object when it was originally found in 1975. Shown here is a speculative illustration of how the irregular moon might be shaped.

Moons of Jupiter: Callisto

Along with Io, Ganymede, and Europa (which is yet to come in this slide show), Callisto is one of the four Galilean satellites. These are the moons of Jupiter that Galileo discovered while looking through a telescope in 1610. Callisto is about the same size as Mercury, and it's a heavily cratered moon that has almost no geological activity. Callisto's surface may also be one of the oldest landscapes in the solar system, including Earth's moon -- about 4 billion years old.

Moons of Jupiter: Thebe

Along with Metis and Adrastea, Thebe was discovered by scientists studying images from the Voyager spacecraft in 1979 and 1980. It's closer to Jupiter than Io is, but it's not so close that it's in danger of losing its altitude. The material in Jupiter's Gossamer ring probably comes from Thebe and another moon, Amalthea.

Moons of Jupiter: Amalthea

Speaking of Amalthea, shown here is an artist's rendition of the mysterious moon (inset: our best real view so far). Astronomers don't know much about it, but they do know it's the reddest body in the solar system. Unlike the other three moons that lie within Io's orbit -- Thebe, Metis and Adrastea -- Amalthea wasn't discovered by the Voyager science team. Edward Emerson Barnard discovered Amalthea it in 1892, and it had been almost 300 years since anyone had discovered a new moon orbiting Jupiter. Before that, the last person to discover a Jovian moon was Galileo.

Moons of Jupiter: S/2000 J11

This not-to-be-named moon marks an interesting dividing line in the wealth of satellites orbiting Jupiter. S/2000 J11, named after it was found in 2000, moves in the same direction that Jupiter spins -- as do all the moons that are closer to the planet. Almost every distant moon, however, orbits in the opposite (retrograde) direction, as this diagram shows. The only known exception is Carpo, sometimes known as Karpo, which was discovered in 2003.

Moons of Jupiter: Europa

About two-thirds of the Earth is covered in water, but Europa has about twice as much water as our home planet. Europa's might surface is covered in ice, but astronomers are almost convinced there is an ocean of liquid water underneath -- an environment shielded from Jupiter's intense radiation that might be hospitable to life. A cold, salty planet might not seem like a good place to live, but there are species on Earth that thrive in just those conditions.

Slideshow originally posted Feb. 2009.