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Enhancing Our View of Europa

Space exploration has been filled with its share of frustrations, the most obvious being the lack of follow-up with travel to the Moon following Apollo 17. That’s been a 50-year gap and counting, but a gap of half that size is also unsettling. It was in late 1995 that the Galileo probe began orbital operations at Jupiter, and since then we’ve had to rely on its imagery of Europa when we needed close up views of the ocean-filled moon. While we await Europa Clipper, scheduled for 2024 launch, and Jupiter Icy Moon Explorer (JUICE), slated by ESA for a departure in 2022, we’re still refining Galileo images in preparation for future flybys.

One thing the newly touched up images should remind us of is that Europa Clipper is going to give us views of much larger parts of Europa’s surface at high resolution, complementing but considerably extending what Galileo was able to do. The latter was a mission with its own set of frustrations, of course, as a recollection of its unusable high gain antenna makes clear, but the superb work by ground controllers in recovering these Europa images is an object lesson in getting the most out of the equipment you’ve got left. Let’s hope Europa Clipper runs into no comparable difficulties.

Image: This image shows a transitional location between blocky chaos terrain, on the left, and ridged plains on the right. A few chaos blocks are visible on the left as individually broken and rotated pieces of preexisting surface material; their shadows indicate that some of these blocks have tilted as well. A ridge passes through the center of this image. These ridges, which contain arc-shaped segments joined together by a series of cusps, may be related to how the icy surface crust of Europa fractures when subjected to stresses from Jupiter’s strong gravity. The right side of this image shows a few lenticulae, which are small rounded surface features, commonly domed in appearance. The image resolution is 247 yards (226 meters per pixel, and this image depicts an area about 180 miles (300 kilometers) across. Credit: Mario Valenti / SETI Institute / NASA/JPL-Caltech.

The three images here were captured on the eighth of Galileo’s targeted flybys, showing features as small as 460 meters in size. They were taken through a clear filter in grayscale, with lower-resolution images from the same region on a different flyby used to map color onto the grayscale, producing, at a cost of considerable time and processing power, what we see here. These are enhanced-color images, thus exaggerating color variations to bring out the chemical composition of the surface. The light blue or white areas are predominantly water ice, while reddish areas are laden with other materials, like salts.

Image: This image shows a region of Europa’s surface covered with ridges and bands, with a few small disrupted chaos regions. Ridges, a common surface feature type, may form when a crack in the surface opens and closes repeatedly, building up a feature that’s typically a few hundred yards tall, a few miles wide and that can stretch horizontally for thousands of miles. In contrast, bands are locations where a crack appears to have continued pulling apart horizontally, producing large, wide, relatively flat features. This image shows both ridges and bands, which interact with each other in complex ways that are somewhat similar to tectonic activity on the Earth. Credit: NASA/JPL-Caltech/SETI Institute.

All three images were captured in the spacecraft’s 17th orbit of Jupiter (E17), with the lower-resolution color images used for mapping taken in orbit E14. The striking thing about the Europan surface has always been its relative youth, some 40 to 90 million years old, meaning what we see is much younger than the moon itself, which would have formed 4.6 billion years ago. This is one of the youngest surfaces in the Solar System, a place of long linear ridges and bands that indicate crustal stretching under the influence of Jupiter’s strong gravity.

Image: A region of blocky chaos terrain, where the surface has broken apart into many smaller chaos blocks that are surrounded by featureless matrix material. Many of the chaos blocks have moved sideways, rotated, or tilted before being refrozen into their new locations, and some larger blocks preserve features of the pre-existing terrain before it was broken up. Using these features as clues, scientists have been able to reconstruct some chaos regions like jjgsaw puzzles to track the motion of blocks. Cutting through the chaos terrain near the bottom, from left to right, is a broad flat band. Called Agenor Linea, it is one of the longest bands on Europa and is distinctive for its two-color appearance, with a bright region at the top and a darker region below. Another rare bright band, Katreus Linea, cuts across the top portion of this image. The image resolution is 243 yards (222 meters) per pixel, and this image depicts an area about 170 miles (280 kilometers) across. Credit: NASA/JPL-Caltech/SETI Institute.

Europa Clipper will conduct numerous flybys of Europa as we try to learn more about the ocean now believed to exist beneath the icy crust, and its interactions with the surface. The disrupted areas known as ‘chaos terrain’ are particularly interesting, as they show blocks of surface material that have been moved through gravitational stresses and then refrozen into a new location. The jigsaw puzzle analogy JPL uses to describe them is exactly on target.

Image: The locations on Europa depicted in the newly processed images, with Chaos Transition at top. This image is centered approximately at 6.4 degrees north latitude, and 135.3 degrees east positive longitude. Credit: NASA/JPL-Caltech/SETI Institute.

Original plans for a Europa orbiter were scrapped at least partly due to concerns over the radiation levels produced by Jupiter’s magnetosphere. Instead, we’ll get over 40 close flybys as Europa Clipper makes its way around the giant planet in an elliptical orbit. The JUICE mission will conduct two Europa flybys of its own, while adding multiple flybys of Callisto before settling into orbit around Ganymede. By the end of this decade, then, we should start updating these spectacular images with high-resolution views of entirely new terrain, and the long wait for a return to Europa will finally end.


Comments on this entry are closed.

  • Alex Tolley May 5, 2020, 12:00

    …and the long wait for a return to Europa will finally end.

    As one of the most important questions is whether Europa has life in its subsurface ocean, this “return to Europa” won’t be established until we have made some serious attempt to do this. First, a lander to sample the material on and just below teh surface at various places, then finally a serious attempt to discover life, whether embedded and frozen in the surface ice, or better, in the ocean itself. The last is obviously very ambitious but would be necessary, especially if surface samplings indicate that biological material is present.

    In teh meantime, we gaze longingly at these images and hope that somewhere someone is constructing 3D flythrough landscapes to further whet out interests in this frozen world.

  • Robert Flores May 5, 2020, 14:57

    Would it have killed NASA to plan for one or two 10 Kilo, simple piggyback probes for Europa with the JUNO mission. Just camera, craft controls, enough propulsion to bring them within 2-3 km from the surface (all contained within a Faraday Cage like protective shell) get pics at 2M resolution, and then power out to be disposed of by
    a Jupiter dive.
    We need to know how hazardous the surface is and if there are rivers of slush. Slush would mean that there is a transfer of surface chemicals to the inner ocean. The slush features would allow easy access to the Ocean below, rather than using expensive self drilling, or Kinetic systems to break through the ice.

    • Andrei May 7, 2020, 19:52

      The ice of Europa is very thick, drilling or explosives will not get far.
      Many models predict basins of intermediate water with ice both above and below that have no contact with the ocean below which is of most interest.
      Our best bet for the foreseeable future is to study the ice on the surface and the compounds closely.
      A hopping lander would have been the best idea to study several sites, but I am afraid that is only a science fiction dream in my lifetime.
      The Russian Laplace-P have been moved from Europa to Ganymede as Roskosmos did not feel confident their lander could cope with the radiation on Europe. And the mission will now fly separately, the pace of development do make it somewhat uncertain they will launch as scheduled in 2022.

  • Gary Wilson May 7, 2020, 13:36

    Surely Europa is the prime target for future large robotic missions as Mars is the prime target for manned missions. The possibility of life in Europa’s ocean is so exciting and would provide us with an enormous amount of information about what types of life can arise is such a setting. First of all can we land and explore the surface, and then can we penetrate the ice and send a submersible of some kind into the ocean? Finally, would we be able to detect life unambiguously? We have been unable to achieve that goal on Mars after several decades of robotic missions so it’s clearly not going to be straightforward even if we do get a probe into the subsurface water of Europa.

    • Andrei May 7, 2020, 19:38

      Europa have been my main target of interest for exploration since the Voyager images. And I am extremely happy to see these happen in my lifetime.
      In my opinion it is possible to get a clear signal of the presence of life from various compounds that are part of any metabolism we can expect in this environment.
      (This contrary to the mission to Titan where the environment is such that we will be less certain regardless of what equipment that can possibly be strapped to Dragonfly – prebiotic chemistry might be able to mimic life.)
      For Europe such cannot be done from orbit but require a lander with a miniature lab. Sadly neither mission did include any and the question of life is hardly likely to be answered from either mission.
      Europa is a difficult target for a mission, I am the first to admit, even though it could be deployed on the hemisphere that receive less radiation. A lander would have to be shielded from the very strong radiation enroute to a landing. And comparably large rocket stage to break and and descend – even so I consider this a lost opportunity.

  • Gary Wilson May 8, 2020, 12:43

    I believe the ice is several km thick on Europa. I thought the earliest models of a lander would use a bullet shaped probe with an RTG or the heat from an RTG to melt it’s way down through the ice pulling a long cable behind. The lander remains on the surface to relay communications to an orbiter for transmission to Earth. Once through the ice sheet a small ROV submersible is released which samples the water. I don’t remember what types of science experiments were to be included in its science package. Surely we would want cameras to record its progress as well. It sounds like a multi-billion dollar mission to me but what an adventure!

  • Patrick Underwood May 10, 2020, 14:36

    What is the consensus on Jovian life itself?

    I mean, just look at it. It’s a gigantic chemistry lab with vast ranges of temperature and pressure. What properties make it a poor bet? Honest question.

    • Robert Flores May 10, 2020, 21:05

      I don’t think any lifeforms could have arisen in Jupiter’s clouds naturally. It is too violent for RNA analogues to survive without a rugged barrier such as a cell wall. Chicken and Egg problem.
      I think it more Probable (still very remote chance) that spores of hydrogen breathing organism of extra-Jupiter origin could have been delivered there. Such spores could have found a way to make a living in places of the upper atmosphere. These could be sparse and we would not spot them (as say Blue-Green Algae on Earth) because of the constant hazards trying to destroy them, these hazards would tend to be of a chaotic nature and therefore not easy to evolve beyond them.

  • David Herne May 11, 2020, 0:25

    I commend the book ‘Unmasking Europa’ by Richard Greenberg to the interested party. From his Planetary Society biography – ‘Greenberg served as a member of the Imaging Team for NASA’s Galileo spacecraft, where his research began to focus on characterizing and interpreting Jupiter’s satellite Europa, which formed the basis for his two books on Europa.’