Juno reports rare close-up of frozen moon Europa

More than 20 years had passed since Europe had been closely watched.

NASA’s Juno probe, which is exploring the vicinity of Jupiter, has returned a rather exceptional image: this is one of the most detailed photographs of Europa, the mysterious frozen moon that accompanies the gas giant.

This shot was captured during its most recent flyby last week, when the spacecraft brushed past this icy world just 350 kilometers above sea level. It’s only the third time a man-made machine has come this close. A position that offered him an impressive view.

A good opportunity to rediscover this icy surface, crossed by long stripes that, seen from the sky, almost look like highways. In fact, they are fracture lines; they are very important structures, since they are the main witnesses of the fascinating geological and hydrological activity of Europe.

This large sphere of ice is much more dynamic than might be thought at first glance; it is covered with huge sheets of ice that bear striking similarities to certain structures on Earth.

© NASA/JPL-Caltech/SwRI

Europe shows what it has in its belly

Most current scientific models suggest that this material is underlain by a second, warmer ice sheet, which exhibits very slow convection movements — a bit like the rock in the Earth’s mantle. On our planet, this convection is an essential component of what is called plate tectonics.

This scientific model allows us to describe the way in which huge blocks of rock, the tectonic plates, move against each other, which generates several important phenomena, such as subduction at the junction zones. The researchers believe that Europa probably exhibits similar phenomena, but with these ice patches; the lines seen in the photos are a manifestation of the physical stresses that the different plates exert on each other.

In the center of the image there is also a less uniform area that contrasts with the rest of the landscape. Specialists have not been able to pinpoint its origin. This could be another consequence of Europe’s domestic activity. We can also see a scar left by a collision with another celestial body.

At the bottom of this structure and in the upper right corner of the image, there are also dark spots in the shape of an ellipse. Planetary scientists consider them manifestations of another remarkable European phenomenon.

On Earth, the internal dynamics of the planet sometimes lead to the appearance of superheated rocky material; then we speak of a volcanic eruption. But the physical phenomena that feed them are not exclusive to the Earth’s mantle; they also exist in Europa, where they give rise to immense eruptions of ice and liquid water. So we talk about cryovolcanismand it is this material that would be the origin of the dark spots.

The most observant will also have noticed the presence of a multitude of small irregular white dots, especially visible in the corners of the image. These do not correspond to structures present on the surface. These are visual artifacts related to extreme radioactivity that exists in this corner of the cosmos. In fact, Europe receives around 5.4 Sv of radiation per day; that’s 1800 times more than a human on Earth at sea level.

ideal conditions

The other interesting element of this observation is that this sensational image was captured using an instrument that was not designed for this purpose at all: the Stellar Reference Unit (SRU). Typically, this camera allows the probe to orient itself by looking at nearby stars, like sailors of yesteryear. In order to display these landmarks, the instrument has been optimized to operate in very low light conditions.

A coincidence, since Juno flew over Europe during the “night”; she was illuminated only by indirect rays of light reflected from Jupiter’s clouds. Therefore, a standard camera would have been almost blind under these conditions. The SRU, on the other hand, had no problem doing so. And thanks to these unique lighting conditions, he was able to capture these icy expanses in amazing detail.

This image unlocks an incredible level of detail in a region never before seen in such revealing resolution and lighting conditions. “Explains Heidi Becker, one of those responsible for these observations, in a press release.

All these surface structures are so intriguing “, She continues. “ Understanding how they formed and how they are connected to the history of Europe will inform us about the internal and external processes that define this icy crust. “.

And then ?

Unfortunately, as brave as she is, Juno will have a hard time figuring out what’s going on under that armor. To find out more, we will have to wait for the arrival of Europa Clipper, the protagonist of another very exciting mission. This machine will leave in 2024 with the aim of landing directly on the surface to discover this moon. He will attempt to unravel the secrets of its geology as he seeks to determine if Europa is likely to harbor extraterrestrial life.

But Juno isn’t going to retreat for that long; she has already proven time and time again that she is capable of going far beyond her initial mission. Originally, she was just to focus on Jupiter. Meanwhile, she brought stunning close-ups of Ganymede, another of Jupiter’s main moons.

With this image of Europa, the probe adds the second of the four Galilean moons to its list. And from 2023, it will do it again with Io during an observation that already promises to be fascinating. This moon is radically opposed to its icy little sister; it is the driest astronomical object ever identified by researchers. It is also the most geologically active object in the solar system, with more than 400 active volcanoes on its surface.

Suffice it to say that Juno is not going to stop there; she still reserves for us images that enthusiasts will devour like hotcakes and that will occupy scientists for years to come.

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