In Photos: See Mysterious ‘Wet Moon’ Europa From Just 219 Miles Above As NASA’s Juno Spacecraft Gets RarClose Look

The Juno spacecraft in orbit of Jupiter since 2016 last week got super-close to one of the top targets of NASA’s hunt for extraterrestrial life.

Its stunning close-up photos of Europa, one of the giant planet’s largest moons, came from Juno’s 45th perijove on September 29, 2022 that saw it get to within just 219 miles/352 kilometers of the moon’s fractured surface.

It was an appetiser for some more super-close flybys of the mysterious moon planned for later in the decade by two new spacecraft that will soon leave Earth.

“It’s very early in the process, but by all indications Juno’s flyby of Europa was a great success,” said Scott Bolton, Juno principal investigator from Southwest Research Institute in San Antonio. “This first picture [above] is just a glimpse of the remarkable new science to come from Juno’s entire suite of instruments and sensors that acquired data as we skimmed over the moon’s icy crust.”

As you can see from these stunning close-ups from Juno’s two-megapixel camera, Europa has a mess of ridges and bands crisscrossing its surface. It’s often referred to as a “chaos terrain” by planetary geologists.

These features are thought to be the result of Jupiter’s strong gravity stretching and pulling on its icy surface. The miles-wide ridges could be cracks that continually open and close. They stretch for thousands of miles.

Juno’s flyby of Europa last week was the third-closest ever performed. The second-closest images came from NASA’s Voyager 2 in 1979, which imaged brown stripes on its surface that suggested cracks. They were followed by NASA’s Galileo spacecraft in 2000, which found evidence for an ocean beneath its surface ice.

The Hubble Space Telescope has glimpsed plumes of water spilling into space, but scientists are unsure whether that was a fluke event, largely because it’s not been observed since.

“The science team will be comparing the full set of images obtained by Juno with images from previous missions, looking to see if Europa’s surface features have changed over the past two decades,” said Candy Hansen, a Juno co-investigator who leads planning for the camera at the Planetary Science Institute in Tucson, Arizona. “The JunoCam images will fill in the current geologic map, replacing existing low-resolution coverage of the area.”

Planetary scientists will soon get an even closer look of Europa.

NASA’s Europa Clipper mission will launch in October 2024 and arrive in late 2027 to perform about 45 flybys of Europa, in each pass photographing the moon’s icy surface in high resolution. Both will likely sail through any plumes of water vapor detected to be erupting from Europa’s ice crust—if there are any.

The European Space Agency’s JUpiter ICy moons Explorer (JUICE) will launch in April 2023, arrive in July 2031 and take three and a half years to examine Europa as well as two of Jupiter’s other Galilean moons, Ganymede and Callisto.

Juno’s recent super-close flyby will help planetary scientists plan what future missions will study. “Being able to get a close flyby with the instruments on Juno is going to help us in understanding how the surface responds to very sensitive near infrared spectrometers and high quality imaging,” said Jonathan Lunine, a planetary scientist at Cornell University and co-investigator on the Juno mission, who works on Europa Clipper.

“Juno’s flyby of Europa isn’t just a dress rehearsal, but I think it may provide some some guidance and what we want to look for with with the much more extensive Europa Clipper mission,” said Lunine.

Juno’s mission is scheduled to end in September 2025, but between now and then it has plenty of work to do. Its extended mission will see it flyby Jupiter’s volcanic moon Io on December 30, 2023 and on February 3, 2024. It will also get very close observations of Jupiter’s higher northern latitudes, which look very different from its lower latitudes.

Juno’s 45th perijove comes as Jupiter reaches its annual opposition in Earth’s night sky. On September 26, 2022, Earth was precisely between Jupiter and the Sun. As a consequence Jupiter is at it brightest of the year, its entire disk is illuminated from our point of view and it also rises in the east at sunset and sets in the west at sunrise. So it’s the very best time to observe Jupiter from Earth.

Meanwhile, Juno will get a ringside seat every 38 days, with the Europa flyby reducing its orbit of Jupiter from 43 days.

Juno’s next close flyby of Jupiter, perijove 46, will take place on November 6, 2022.

Wishing you clear skies and wide eyes.