Fascinating sight: NASA’s Juno spacecraft flew over Jupiter’s moon Europa at just 412 kilometers – taking the first close-up image of the icy moon in more than 20 years. The high-resolution image shows a 150-kilometer section of the ice surface, which is characterized by cracks, bulges and mysterious dark deposits. What causes these structures and what the ocean is like under the ice crust has only been partially clarified so far.
Of the Jupitermond Europa is considered one of the most promising places for extraterrestrial life in the solar system. For under its icy crust, this moon has a salty one, followed by warm ones currents criss-crossed ocean of liquid water. Even hydrothermal vents and maybe even volcanoes might exist at the bottom of this subglacial ocean. Water vapor fountains and cracks in the ice are also evidence of an active exchange with the ice surface. So far, Europe has only received visitors in the form of close flybys Voyager space probesas well as NASA’s Galileo spacecraft in the 1990s.
Overflight at an altitude of only 412 kilometers
Now NASA’s Juno spacecraft has also made a close flyby of Jupiter’s moon. On September 29, 2022, it flew over the icy surface of Europe at a distance of only 412 kilometers. The probe aimed the camera of its Stellar Reference Unit (SRU) – an optic actually intended for navigation with the help of the stars – at the surface of Jupiter’s moon. During its passage at a speed of 24 kilometers per second, this camera created this 150 by 200 kilometer image.
The SRU camera is specially designed for sharp images in low light. It was therefore perfectly suited to taking pictures of the moon’s night side, which is only weakly illuminated by Jupiter’s reflection. This lighting allows the surface structures to stand out particularly clearly. “This image reveals an incredible amount of detail at a high resolution and in the most favorable lighting conditions ever seen,” says Heidi Becker, one of the Juno mission’s science directors.
Cracks, rips and dark spots
The image shows part of Jupiter’s moon’s icy crust, which is criss-crossed by numerous fine trenches and double ribs. Dark deposits on the ice can be seen in several places, including the top right, the right edge and below the center of the image. The researchers suspect that these might be traces of eruptions. The rounded structure in the center of the image is almost 75 kilometers long and around 37 kilometers wide. However, its origin is so far unclear.
“These features are extremely exciting,” says Becker. “Understanding how they were formed and how they are linked to Europa’s history can tell us more regarding what internal and external processes shape the moon’s icy crust.” and analyze data from their scientific instruments from the Europa flyby more closely.
Data analysis has only just begun
Juno is actually primarily a space probe designed for exploring Jupiter, orbiting the gas giant in elliptical orbits that are sometimes extremely close to it. But NASA has already adjusted its trajectory several times to allow the spacecraft to fly close by some of Jupiter’s large inner moons. In June 2021 Juno passed Ganymede in this meadow, in 2023 a close approach to the volcanic moon Io is planned.
“Our team is really excited that we were able to extend the objectives of our expanded mission to allow Juno to visit three of Galilean’s four moons and Jupiter’s rings,” said Scott Bolton, director of the mission, of the Southwest Research Institute. “With the current flyby on Europa, Juno has now seen two of Jupiter’s most interesting moons up close.” The Juno data and images of Europa should also help specify the goals of NASA’s Europa Clipper mission, planned for the 2030s .
Quelle: NASA Jet Propulsion Laboratory