NASA finds 'glass-smooth lake of cooling lava' on Jupiter's moon Io

Among all of the moons in our solar system, Jupiter’s Io, stands out for many reasons. Io is an incredibly active and extreme place, with glistening lava lakes and volcanic eruptions sending sulfur and magma shooting high above the surface.

This tiny but powerful moon with the hellish landscape has drawn attention for good reason. Many see it as a window into the deeper processes that shaped the solar system’s largest planet.

Studying data from the Juno Mission, researchers are working to understand how these processes affect not only Io, but also Jupiter’s entire family of moons.

Scott Bolton, Juno’s principal investigator at the Southwest Research Institute (SWRI) in San Antonio, is among the experts examining recent findings from Juno’s most recent flyby of Io.

Io’s volcanoes and lava lakes

Io’s volcanic prowess is, by far, the biggest in the solar system. Jupiter’s forceful gravity pulls at it, while neighboring moons add constant tension.

That grinding generates intense heat below the surface, driving eruptions strong enough to fling volcanic material hundreds of miles away.

These eruptions contribute to Io’s bright coloring. Yellow, red, and white shades result from sulfur and volcanic flows.

Though the scenery looks vivid, the environment remains extremely harsh, with a thin atmosphere and unrelenting radiation.

Hellish landscape captured by Juno

Constant volcanic eruptions reshape Io so often that its surface rarely looks the same for long. Peaks of cooled lava can appear in one place, only to be obscured or replaced after another outburst.

Its swirling landscape of molten sulfur and rocky terrain has intrigued observers since the days of early flybys. But the moon’s environment is far too toxic and irradiated for any typical form of life.

NASA’s Juno spacecraft, launched in 2011, has been exploring Jupiter and its satellites for years. Two close flybys of Io provided the first close-up images of the moon’s northern regions.

During these passes, Juno came within about 930 miles of Io’s surface.

Mission scientists turned these encounters into animations that feature a towering mountain and a very smooth lake of cooling lava. Their findings suggest there is more variety in Io’s terrain than expected.

“Glass-smooth” lava lake found on Io

“Io is simply littered with volcanoes, and we caught a few of them in action,” Bolton enthused. “We also got some great close-ups and other data on a 200-kilometer-long (127-mile-long) lava lake called Loki Patera.”

There is amazing detail showing these lava lake islands embedded in the middle of a potential magma lake rimmed with hot lava.

The specular reflection our instruments recorded of the lake suggests parts of Io’s surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth.

Scientists also used Juno’s tools to compare the reflectivity of different areas. The lake’s sheen points to surfaces that cooled rapidly.

Those island-like structures highlight the dynamic nature of Io’s volcanic basins, which can form striking contrasts against the glassy terrain.

First look at Io’s South Pole

Researchers employed the Microwave Radiometer (MWR) to assess temperature levels.

Maps revealed that Io’s poles run colder than its middle latitudes, supporting the idea that constant volcanism may be concentrated elsewhere.

The data also suggest a surface smoother than those of other large Jovian moons.

This method of measuring heat below and above the surface adds depth to what cameras capture from orbit.

The repeated flybys will refine the knowledge of Io’s temperatures, offering fresh angles on how eruptions shape local regions.

Polar cyclones on Jupiter

During Juno’s extended mission, the spacecraft positions itself closer to Jupiter’s north pole with each pass, letting the MWR instrument get better views of the planet’s swirling cyclones. They do not behave in a uniform way.

“Perhaps the most striking example of this disparity can be found with the central cyclone at Jupiter’s north pole,” explained Steve Levin, Juno’s project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Southern California.

“It is clearly visible in both infrared and visible light images, but its microwave signature is nowhere near as strong as other nearby storms. This tells us that its subsurface structure must be very different from these other cyclones.”

The MWR team continues to collect more and better microwave data with every orbit, so we anticipate developing a more detailed 3D map of these intriguing polar storms.

Hunting for Jupiter’s water

A main science goal for Juno is to clarify Jupiter’s water content. The team is not looking for liquid water but tracking oxygen and hydrogen in the planet’s atmosphere.

Learning how much water Jupiter holds clarifies how the solar system formed.

In 1995, NASA’s Galileo probe sampled the atmosphere for nearly an hour. Its data showed a region that seemed nearly devoid of water, contradicting earlier computer models.

Juno’s approach seeks to determine if Galileo happened to land in a dry spot.

“The probe did amazing science,” Bolton said, “but its data was so far afield from our models of Jupiter’s water abundance that we considered whether the location it sampled could be an outlier.”

For years, scientists were left wondering if the spot where the Galileo probe entered Jupiter’s atmosphere had skewed the results. Without more data, there was no way to know for sure.

“But before Juno, we couldn’t confirm,” Bolton explained.

Microwave Radiometer (MWR)

That changed with the Juno mission. Using data from its Microwave Radiometer (MWR), researchers were finally able to get a clearer picture.

“Now, with recent results made with MWR data,” Bolton said, “we have nailed down that the water abundance near Jupiter’s equator is roughly three to four times the solar abundance when compared to hydrogen.”

In other words, the Galileo probe had entered a rare, unusually dry region of the planet – something Bolton described as “an anomalously dry, desert-like region.”

These results support the belief that water-ice material could have supplied heavy elements during Jupiter’s early growth.

Yet Juno’s findings on the gas giant’s core point to a low amount of water in that interior, posing a fresh challenge for scientists.

What happens next?

Data gathered through the rest of Juno’s extended mission will help experts compare water levels in Jupiter’s polar areas with those at the equator.

It may also reveal new details about the planet’s diluted core and how it formed.

The mission continues to deliver insights about the largest planet in our solar system – and about Io, the small but forceful moon that refuses to be overlooked.

More information about Juno is available at: https://www.nasa.gov/juno

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