Juno reports an exceptional close-up of the frozen moon Europa

It had been more than 20 years since Europa had been closely observed.

NASA’s Juno probe, which is exploring the vicinity of Jupiter, has brought back a rather exceptional image: here is one of the most detailed photographs of Europe, the mysterious icy moon that accompanies the gas giant.

This shot was captured during his most recent flyby last week, when the craft skimmed this frozen world just 350 kilometers above sea level. It is only the third time that an artificial machine has come this close. A position that offered him a breathtaking view.

A good opportunity to rediscover this frozen surface, crossed by long streaks that, seen from the sky, would almost seem like motorways. They are in fact lines of fracture; they are very important structures, as main witnesses of the fascinating geological and hydrological activity of Europe.

This large ice sphere is much more dynamic than one might think at first glance; it is covered with huge ice sheets that have striking similarities to some structures on Earth.

© NASA / JPL-Caltech / SwRI

Europe shows what it has in its belly

Most current scientific models suggest that this material underlies a second warmer layer of ice, which it shows very slow convection movements – a bit like the rock of 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 relative to each other, which generates various important phenomena such as subduction in the junction zones. Researchers believe Europa likely exhibits similar phenomena, but with these patches of ice; the lines that can be 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 accurately determine its origin. This could be another consequence of Europe’s internal activity. We can also see a scar left by a collision with another celestial body.

In the lower part of this structure and in the upper right corner of the image there are also some dark spots in the shape of an ellipse. Planetary scientists see them as manifestations of another notable European phenomenon.

On Earth, the internal dynamics of the planet sometimes lead to the emergence of superheated rock material; we therefore speak of volcanic eruption. But the physical phenomena that feed them are not exclusive to the earth’s mantle; they also exist on Europe, where they give rise to immense eruptions of ice and liquid water. Then let’s talk about cryovulcanismand it is this material that would be the origin of the dark spots.

The more attentive will also have noticed the presence of a multitude of small irregular white dots, particularly visible at 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 about 5.4 Sv of radiation per day; this is 1800 times of a human being on Earth at sea level.

Ideal conditions

The other interesting element of this observation is that this stunning image was captured using a tool that was by no means intended for this purpose: the Stellar Reference Unit (SRU). Usually, this camera allows the probe to orient itself by observing nearby stars, just like navigators of the past. In order to see these landmarks, the instrument has been optimized to operate in very low light conditions.

One possibility, given that Juno flew over Europe during the “night”; it was illuminated only by indirect rays of light reflected from Jupiter’s clouds. A standard camera would therefore have been nearly blind under these conditions. The SRU, on the other hand, had no problem doing this. And thanks to these very special lighting conditions, she was able to capture these icy expanses in amazing detail.

This image unlocks an incredible level of detail in a region never seen before at such resolution and under such revealing lighting conditions. Heidi Becker, one of the people responsible for these remarks, explains in a press release.

All of these surface structures are so intriguing “, keep on. “ 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 frozen crust. “.

And then ?

Unfortunately, valiant as she is, Juno will have a hard time understanding what is 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 start in 2024 with the aim of landing directly on the surface to get to know this moon. He will attempt to unravel the secrets of his own geology while trying to determine if Europa is likely to harbor extraterrestrial life.

But Juno won’t retire for so long; he has already proven time and time again that he is capable of going far beyond his initial mission. Originally, he was just to focus on Jupiter. Meanwhile, he has brought back beautiful close-ups of Ganymede, another of Jupiter’s major moons.

With this image of Europa, the spacecraft adds the second of the four Galilean moons to its list. And from 2023 he will do it again with Io during an observation that already promises to be fascinating. This moon is radically opposite to its frozen 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 will not stop there; he still has images in store for us that fans will devour like hot cakes and that will occupy scientists for many years.

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