• NASA's Juno probe zipped by Jupiter's icy moon Europa on Thursday.
• Researchers observed Europa's surface and the ocean underneath the moon's icy crust.

On Thursday morning, NASA's Juno spacecraft flew within 219 miles of the surface of Europa, a large icy moon that orbits Jupiter. It's humanity's closest look at the frozen world in more than 20 years.

The Juno mission launched in 2011 to study Jupiter, the largest planet in the solar system. After it successfully completed its primary mission in 2021, the Juno team used the probe to learn about Jupiter's moons, including Europa, Ganymede, and Io.

During Thursday's flyby, Juno made important observations about Europa, including taking high-resolution images of its surface. Juno's visit follows NASA's Galileo spacecraft, which last flew by Europa in 2000.

"This first picture 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," Scott Bolton, Juno principal investigator, said in a press release.

The first raw images from Juno's close approach to Europa started beaming back to Earth Thursday afternoon. The fresh snapshots, along with decades-old images taken by the Galileo spacecraft, provide important insights about the frozen world.

At 5:36 a.m. ET, the spacecraft made its closest approach to Europa, zipping by 219 miles above the surface. Juno was in Europa's shadow, but sunlight reflecting off Jupiter provided enough light for the probe's camera to capture images.

The above left image, taken by Galileo in 1997, is an approximate natural color image of Europa and showcases the stunning diversity of Europa's surface geology. Above right is a raw image of the Juno probe looking toward Europa on September 29. Both images show long linear cracks and ridges traversing the moon's surface.

After processing the new images, researchers hope comparing them to images of Europa from previous missions could reveal how the icy moon has changed over decades.

"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," Candy Hansen, a Juno co-investigator who leads planning for JunoCam, the probe's visible light camera, said in a press release.

"The JunoCam images will fill in the current geologic map, replacing existing low-resolution coverage of the area."

Europa has an ice shell, which is thought to be between 10 and 15 miles thick. Astronomers believe a salty ocean, estimated to be 40 to 100 miles deep, is hidden beneath its thick icy surface. That's a big deal in our search for life beyond Earth, since liquid water is one of the essential ingredients for all living organisms.

Juno is equipped with powerful instruments that can peer beneath Europa's ice crust, gathering data on its composition and temperature, according to NASA.

In the close-up image above, taken by the Galileo spacecraft in 1997, you can see Europa's surface crisscrossed with cracks along its icy exterior. Previous missions spied plumes of water vapor erupting through that frozen shell. The Juno team is still processing images from Thursday's flyby, but scientists hope they captured plumes shooting from Europa's surface.

What Juno learns from the flyby could inform future missions, including NASA's Europa Clipper probe, which is set to launch in 2024 to obtain more data on the ocean beneath its icy crust and how it interacts with the surface.

"Thanks to the ingenuity of the navigation team, Juno's trajectory was adjusted to cross the Jovian moon's orbit at the right time, giving us very valuable data for the Europa Clipper mission!" Gregory Dubos, Systems engineer for the Europa Clipper mission, tweeted on Thursday.

That mission may help scientists determine whether the interior ocean exists and if the moon has the potential to be habitable for life.