Then NASA Juno spacecraft came closest Jupiter‘s moon Europe in September 2022, it captured evidence not only of briny layers of water connected to the world’s deep subsurface ocean, but also of potential scars formed by towering plumes of water vapor – and it captured that evidence on camera
The majority of the Juno mission’s images were captured by an instrument called JunoCam, which scientists revealed was able to capture four high-resolution images of Europa’s surface as it raced past the icy moon at an altitude of just 355 kilometers (220 miles). The spacecraft also used the Stellar Reference Unit (SRU), which is normally used for imaging weak spots stars, to help Juno navigate. However, on this occasion the SRU’s low-light capabilities were adapted to capture a single image of the night side of Europe. This is the side that only shines when the light is reflected from Jupiter’s cloud tops – we call it ‘Jupiter shine’.
Related: NASA’s Juno probe captures fantastic images of Jupiter’s volcanic moon Io (video)
The SRU has found an unusual feature that has been nicknamed “the Platypus” because of its shape. Formally speaking, it is what is known as chaos terrain: a jumble of ice blocks, ridges, hills and reddish brown spots. There has been chaos on the surface of Europa since the days of the Voyager missions, and planetary scientists suspect that such areas could be areas where briny fluid seeps to the surface, partially melting the icy crust.
The platypus is enormous, spanning 37 kilometers by 67 kilometers (23 miles by 42 miles). Because Europa’s icy surface tends to smooth itself out over geologically short areas time spans, obliterating surface features such as craters, then the Platypus must be one of the youngest features on Jupiter’s moon.
“These features indicate current surface activity and the presence of subsurface liquid water on Europa,” said Heidi Becker, NASA’s SRU principal investigator Jet propulsion laboratoryin a rack. Becker further suggests that the Platypus will be a prime target for both NASAs Europa Clipper mission, which will start later this year, and the European JUICE mission, namely already on the way to Jupiter.
Fifty kilometers north of the Platypus are potentially even more exciting features: a series of double ridges flanked by dark spots on the surface. Such features have previously been seen elsewhere in Europe and are believed to be a point of origin plumes of water vapor that squirt inside roomwith an altitude of 200 kilometers (120 miles).
The elusive plumes have since been somewhat controversial Hubble Space Telescope I first saw them in 2012. But different Saturn‘s moon Enceladuswhere plumes are a predictable and common phenomenon, Europa’s plumes were somewhat spotty, leading some researchers to doubt whether plumes even exist on Europa. The discovery of trenches, somewhat analogous to the tiger stripes on Enceladus – the origin points of the world’s plumes – Europa Clipper and JUICE will also provide regions to focus on in their search for the plumes on Europa.
However, Juno has also found strong evidence that these features, and the surface as a whole, are shifting under Juno’s metaphorical feet. Scientists call it “true polar walk,” meaning the geographic locations of the poles swing across the moon while the ice crust effectively floats on the subsurface global ocean.
“True polar wander occurs when Europa’s icy shell becomes disconnected from its rocky interior, resulting in high stress levels on the shell, leading to predictable fracture patterns,” said Candy Hansen, Juno co-investigator at the Planetary Science Institute in New York. Arizona.
Juno imaged these fault patterns as irregularly shaped depressions with steep walls between 20 kilometers and 50 kilometers in size (12 miles to 31 miles).
“This is the first time that these fracture patterns have been mapped [Europa’s] southern hemisphere, indicating that the effect of true polar wandering on the surface geology of Europe is more extensive than previously identified,” Hansen said.
The results of JunoCam’s in-flight images of Europe were published in March The Planetary Science Journaland the SRU results were published in the journal in December 2023 JGR planets.