Citizen Scientist Captures Glimpse of Jupiter’s Moons, Io and Europa, Using Juno Space Probe Data

The natural satellites are seen in the distant background of the gas giant’s portrait

An image of Jupiter with two of its moons in the distant background. Io and Europa circled in yellow.
The moons appear as two blurry dots located close together in the upper right area of the image. Io, seen as a darker speck on the left of the two dots, is the most volcanically active world in the solar system. Europa is seen on the right and features a global ocean beneath its icy surface.  NASA/JPL-Caltech/SwRI/MSSS/Andrea Luck

NASA's Juno spacecraft snapped a stunning portrait of Jupiter during the probe's 39th close encounter of the planet on January 12, 2022. Two of the giant planet's moons, Io and Europa, photobombed the shot in the distant background. In the upper right of the image, the two moons appear as barely visible small dots. When the photo was taken, Juno was about 38,000 miles above Jupiter with a latitude of nearly 52 degrees south, reports Space.com's Samantha Mathewson.

The images released by NASA were processed by a citizen scientist, Andrea Luck, who used raw data collected by the probe's JunoCam. Images captured by JunoCam are available online for the public to view and process, a statement explains. The JunoCam is NASA's first camera dedicated to public outreach and has captured remarkable views of the Jovian system and its many moons.

In a zoomed-in image released by NASA on March 16, Io and Europa are seen as small cloudy orbs compared to Jupiter's colossal size. Named after Galileo Galleli who discovered the pair in 1610, Io and Europa are the smallest Galilean moons of Jupiter's many natural satellites. Both are about the size of Earth's moon, reports John Wenz for Inverse.

An image of planet Jupiter partially shrouded in shadow.
The images released by NASA were processed by a citizen scientist, Andrea Luck, who used raw data collected by the probe's JunoCam. NASA/JPL-Caltech/SwRI/MSSS/ Andrea Luck

Io, seen as a darker speck on the left of the two dots, is the most volcanically active moon in the solar system. Hundreds of volcanoes riddle its surface with some shooting lava fountains dozens of miles high. Lakes of molten silicate lava also cover Io's surface. The red-hot moon is caught in a gravity tug-of-war between Jupiter and other moons, Europa and Ganymede, which fuels volcanic eruption on the celestial body. As Io is squeezed and stretched by Jupiter's massive gravitational pull, its molten interior is expelled into space, per Inverse.

In contrast, Europa has an icy surface that shrouds an underground global ocean of liquid water. The moon is the smallest out of Jupiter's four giant Galilean moons. Previous observations have shown possible water plumes exploding from the moon's southern region, indicating that water from a subsurface ocean may be pulsing through its icy crust, Space.com reports.

Though it's only the size of Earth's moon, Europa's global ocean contains more water than all of planet Earth. Astronomers suspect the celestial body is one of the best places to find life outside planet Earth, Inverse reports. Later in fall this year, the Juno space probe is expected to make its closest visit to Europa, where it will capture the moon in greater detail, according to a statement from NASA.

In October 2024, NASA plans to launch the Europa Clipper space probe, which will investigate whether the frosty world could sustain life. In 2023, the European Space Agency will also launch its Jupiter Icy Moon Explorer (JUICE) mission to study Jupiter and three of its largest moons: Ganymede, Callisto and Europa.