NASA’s Juno Discovers Glass-Smooth Lake of Cooling Lava on Surface of Jupiter’s Moon Io

Scientists have unveiled groundbreaking discoveries from NASA's Juno mission to Jupiter. This solar-powered spacecraft has provided unprecedented close-ups of the captivating features of the Jovian moon Io, marking a significant milestone in our understanding of the Solar System.

Glassy Lava Lake

In December 2023 and January 2024, the Juno probe swept within 930 miles (1,500 kilometers) of Io, offering the closest look ever at Jupiter's innermost large moon. Scientists used the data gathered from these flybys to make animations of the features of its surface.

The new images have unveiled the awe-inspiring Loki Patera, a 127-mile-long (200 kilometers) lava lake on Io's surface. This captivating sight, which has been observed by astronomers for decades, sits over the magma reservoirs under the moon's surface, adding to the intrigue of Io's geology.

During a news conference held on April 16 at the European Geophysical Union General Assembly in Vienna, Austria, Juno mission principal investigator Scott Bolton described the possible cause for this formation. According to him, the cooling lava at the lake's center is surrounded by possibly molten magma around the edges. Meanwhile, the interior of the lava lake is crowded by rugged islands of rock.

Bolton also revealed that the reflection recorded by their instruments suggests parts of Io's surface are as smooth as glass, resembling the obsidian glass volcanically created on Earth. This smoothness is a significant finding as it indicates a lack of significant geological activity in those areas, providing valuable insights into the moon's geology. Instruments from the Juno spacecraft have determined that Io's surface is smoother than Jupiter's three other moons - Callisto, Ganymede, and Europa. Io is a bit larger than the Earth's moon, and the surfaces that are not molten are mainly covered with sulfur dioxide and yellow sulfur.

Discovered by Galileo Galilei in 1610, Io is the most geologically active celestial object in the Solar System. Its surface is full of hundreds of volcanoes, some of which can release plumes of sulfur and sulfur dioxide hundreds of miles into space. This extreme volcanic activity is mainly due to tidal heating, a phenomenon that results from the gravitational forces exerted by Jupiter and some of its other moons. These forces cause intense internal friction deep inside Io's interior, leading to the moon's unique geological conditions.

Io's surface is primarily composed of sulfur and silicate rock, while its thin atmosphere is mainly sulfur dioxide with small amounts of sodium chloride, oxygen, atomic sulfur, and sulfur monoxide.

Exploring the Features of Jupiter

The flybys have helped reveal more details about Io, but its main purpose is studying Jupiter. Juno's Microwave Radiometer (MWR) , a key instrument on board, will be used to study the water content of Jupiter's atmosphere and the cyclones that blow across its north pole. The MWR works by measuring the microwave radiation emitted by Jupiter, which can provide valuable information about the planet's atmospheric composition and dynamics.

During its extended mission, Juno flies closer to the north pole of Jupiter with each pass. This changing orientation is not a random occurrence but a carefully planned maneuver that enables the MWR instrument to enhance its resolution of the planet's northern polar cyclones. The data permits multiwavelength comparisons of the poles, suggesting that not all polar cyclones are created equal. This approach allows scientists to gather more detailed and comprehensive data about Jupiter's atmospheric dynamics.

The other primary goal of the Juno mission is to collect data that can help understand Jupiter's water abundance. To make this possible, the Juno science team does not hunt for liquid water. Instead, they use a method called spectroscopy to measure the presence of hydrogen and oxygen molecules in the planet's atmosphere. This estimation will be vital in putting together the pieces of evidence regarding the formation of our Solar System.