In September 2022, NASAs Juno spacecraft made a flyby, coming within 355 kilo-metres of the surface of Europa (one of Jupiter’s moon) Since the encounter, scientists have been exploring the images and have identified regions where brine may have bubbled to the surface. The evidence not only captured pockets of binary water which is connected to deep surface ocean but also scars that were formed as a result of towering plumes of water vapors.
Juno was launched to Jupiter on 5 August 2011, from the Cape Canaveral site. JUNO travelled around 3 billion kilo-metres and at Jupiter on 4 July 2016 and in September 2022 made its closest flyby of Europa. The frozen world is the second of the four Galilean satellites that were discovered by Galileo over 400 years ago. Visible in small telescopes, the true nature of the moon is only detectable by visiting craft like Juno.
During its close fly-by, one of the onboard cameras, took four highest resolution images of Europa since Galileo took a flyby in 2000. The images supported the long held theory that the icy crusts at the north and south poles are not where they used to be. Another instrument on board, known as the Stellar Reference Unit (SRU), revealed possible activity resembling plumes where brine may have bubbled to the surface however, the SRU’s low-light capabilities were adapted to take one image of the night-side of Europa. This is the side that shines only with light reflected off the cloud-tops of Jupiter — we call it “Jupiter-shine.”
The SRU found an unusual feature nicknamed as “the Platypus” because of its shape. Formally speaking, it is what’s known as chaos terrain a jumble of ice blocks, ridges, hummocks and ruddy-brown stains. The platypus is huge, spanning 37 kilometers by 67 kilometers, because of which Europa’s icy surface tends to smooth itself out over geologically short time spans, erasing surface features such as craters, then the Platypus must be one of the youngest features on the Jovian moon.
“These features hint at present-day surface activity and the presence of subsurface liquid water on Europa,” said Heidi Becker, who is the SRU’s lead co-investigator at NASA’s Jet Propulsion Laboratory,
However, Juno has also found powerful evidence that the surface as a whole, are shifting beneath Juno’s metaphorical feet and is called as “true polar wander” by the Scientists.
“True polar wander occurs if Europa’s icy shell is decoupled from its rocky interior, resulting in high stress levels on the shell, which lead to predictable fracture patterns,” said Candy Hansen, who is a Juno co-investigator at the Planetary Science Institute in Arizona.
Juno imaged these fracture patterns in the form of steep-walled, irregularly shaped depressions between 20 kilometers and 50 kilometers in size.
“This is the first time that these fracture patterns have been mapped in southern hemisphere, suggesting that true polar wander’s effect on Europa’s surface geology is more extensive than previously identified,” said Hansen.
The results of JunoCam’s images of Europa during the flyby were published in March in The Planetary Science Journal, and the SRU results were published in December 2023 in the journal JGR Planets.
