“Observations from the spacecraft’s pass of the moon provided the first close-up in over two decades of this ocean world, resulting in remarkable imagery and unique science.
The first picture NASA’s Juno spacecraft took as it flew by Jupiter’s ice-encrusted moon Europa has arrived on Earth. Revealing surface features in a region near the moon’s equator called Annwn Regio, the image was captured during the solar-powered spacecraft’s closest approach, on Thursday, Sept. 29, at 2:36 a.m. PDT (5:36 a.m. EDT), at a distance of about 219 miles (352 kilometers).
This is only the third close pass in history below 310 miles (500 kilometers) altitude and the closest look any spacecraft has provided at Europa since Jan. 3, 2000, when NASA’s Galileo came within 218 miles (351 kilometers) of the surface.
Europa is the sixth-largest moon in the solar system, slightly smaller than Earth’s moon. Scientists think a salty ocean lies below a miles-thick ice shell, sparking questions about potential conditions capable of supporting life underneath Europa’s surface.
This segment of the first image of Europa taken during this flyby by the spacecraft’s JunoCam (a public-engagement camera) zooms in on a swath of Europa’s surface north of the equator. Due to the enhanced contrast between light and shadow seen along the terminator (the nightside boundary), rugged terrain features are easily seen, including tall shadow-casting blocks, while bright and dark ridges and troughs curve across the surface. The oblong pit near the terminator might be a degraded impact crater.
With this additional data about Europa’s geology, Juno’s observations will benefit future missions to the Jovian moon, including the agency’s Europa Clipper. Set to launch in 2024, Europa Clipper will study the moon’s atmosphere, surface, and interior, with its main science goal being to determine whether there are places below Europa’s surface that could support life.
As exciting as Juno’s data will be, the spacecraft had only a two-hour window to collect it, racing past the moon with a relative velocity of about 14.7 miles per second (23.6 kilometers per second).
“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 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.”
During the flyby, the mission collected what will be some of the highest-resolution images of the moon (0.6 miles, or 1 kilometer, per pixel) and obtained valuable data on Europa’s ice shell structure, interior, surface composition, and ionosphere, in addition to the moon’s interaction with Jupiter’s magnetosphere.
“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.”
Juno’s close-up views and data from its Microwave Radiometer (MWR) instrument will provide new details on how the structure of Europa’s ice varies beneath its crust. Scientists can use all this information to generate new insights into the moon, including data in the search for regions where liquid water may exist in shallow subsurface pockets.
Building on Juno’s observations and previous missions such as Voyager 2 and Galileo, NASA’s Europa Clipper mission, slated to arrive at Europa in 2030, will study the moon’s atmosphere, surface, and interior – with a goal to investigate habitability and better understand its global subsurface ocean, the thickness of its ice crust, and search for possible plumes that may be venting subsurface water into space.
The close flyby modified Juno’s trajectory, reducing the time it takes to orbit Jupiter from 43 to 38 days. The flyby also marks the second encounter with a Galilean moon during Juno’s extended mission. The mission explored Ganymede in June 2021 and is scheduled to make close flybys of Io, the most volcanic body in the solar system, in 2023 and 2024.”