Scientists on NASA’s Juno mission on Jupiter turned data collected during two recent flybys of Io into animations that highlight two of the moon’s most dramatic features: a mountain and a nearly smooth lake of cold lava. Other recent science results from the solar-powered spacecraft include updates on Jupiter’s polar cyclones and water abundance.

The new findings were announced Wednesday, April 16, by Juno’s principal investigator, Scott Boltonduring a press conference at the General Assembly of the European Geophysical Union in Vienna.

According to NASA, the Juno mission made extremely close flybys of Io in December 2023 and February 2024, coming within about 1,500 kilometers of the surface, taking the first close-up images of the moon’s northern latitudes.

“Io is just full of volcanoes, and we caught some of them in action,” Bolton said. “We also have some great close-ups and other data of a 200-kilometer (127-mile-long) lava lake called Loki Patera. There is amazing detail showing these crazy islands embedded in the middle of a potentially magma lake surrounded by hot lava. The specular reflection recorded by our instruments for the lake suggests that parts of Io’s surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth.”

Maps created with data collected by the Juno mission’s Microwave Radiometer (MWR) instrument reveal that Io not only has a surface that is relatively smooth compared to Jupiter’s other Galilean moons, but also has poles that are cooler than the middle geographic latitudes.

One of the mission’s primary science goals is to collect data that could help scientists better understand Jupiter’s water abundance. To do this, Juno’s science team isn’t looking for liquid water. Instead, they are trying to quantify the presence of oxygen and hydrogen molecules (the molecules that make up water) in Jupiter’s atmosphere. An accurate estimate is critical to piecing together the puzzle of our solar system’s formation.

Jupiter was probably the first planet to form and contains most of the gas and dust that had not been incorporated into the Sun. The abundance of water also has important implications for the gas giant’s meteorology (including how Jupiter’s wind currents flow) and its internal structure.

In 1995, NASA’s Galileo probe provided an early data set on Jupiter’s water abundance during the spacecraft’s 57-minute descent into the Jovian atmosphere. But the data raised more questions than answers, indicating that the gas giant’s atmosphere was unexpectedly hot and — contrary to what computer models had shown — devoid of water.

“The probe did amazing science, but its data was so far from our models of Jupiter’s water abundance that we wondered if the location it sampled might be an outlier. But before Juno, we couldn’t confirm,” Bolton said. “Now, with the recent results done with MWR data, we have concluded that the abundance of water near Jupiter’s equator is about three to four times the solar abundance compared to hydrogen. This conclusively shows that the entry site of the Galileo probe was an unusually dry desert-like region.

The results support the belief that during the formation of our solar system, water-ice material may have been the source of heavy element enrichment (chemical elements heavier than hydrogen and helium accreted from Jupiter) during formation of the gas giant. Jupiter’s formation remains puzzling because Juno’s results in the gas giant’s core suggest a very low abundance of water—a mystery scientists are still trying to solve.

Data during the rest of Juno’s extended mission may help, both by allowing scientists to compare Jupiter’s water abundance near the polar regions with the equatorial region and by shedding additional light on the structure of the planet’s thin core.

During Juno’s most recent flyby of Io on April 9, the spacecraft came within about 10,250 miles (16,500 kilometers) of the moon’s surface. It will make its 61st flyby of Jupiter on May 12.