Astrobiologists \u2013 scientists who look for signs of life beyond the confines of our planet \u2013 have long adhered to a simple mantra: follow the water. That\u2019s because every living thing on Earth, from the tiniest bacterium to the mighty blue whale, needs liquid water to survive. While alien life without water may be possible, looking for that molecular marriage between hydrogen and oxygen is an excellent place to start.<\/p>\n
In the hunt for H\u2082O, much has been made of the habitable zone<\/a> \u2013 the narrow ring around a star where the temperature is just right for liquid water. Earth sits in this region, so the majority of our water neither freezes nor boils. But the habitable zone is an imperfect concept.<\/p>\n \u201cAt least five objects in the outer Solar System<\/a> have sub-surface oceans,\u201d says Dr Mark Fox-Powell<\/a>, an astrobiologist at the Open University. All are far beyond the outer reaches of the traditional habitable zone. Three of these oceans can be found beneath the surfaces on a trio of Jupiter\u2019s moons: Europa, Ganymede and Callisto<\/a>. Jupiter has a habitable zone of its own. The required heat isn\u2019t coming from the Sun, but from the gravity of Jupiter. It expands and contracts the moons, warming them up like squash balls.<\/p>\n While we have been to the Jovian system many times, these moons have rarely been the main attraction. \u201cThe last time we were there studying them directly was with the Galileo spacecraft in the 1990s,\u201d says Fox-Powell. Instead, the focus has tended to fall on the giant planet itself. But now there\u2019s JUICE, a dedicated mission heading for its icy satellites.<\/p>\n Read more about Jupiter:<\/strong><\/p>\n At the heart of the JUICE mission is a spacecraft that\u2019s been built by the European Space Agency (ESA)<\/a>. It bears a slight resemblance to a giant bird, with solar panel wings stretching out on either side of the spacecraft\u2019s main body. The sunlight at Jupiter is 30 times dimmer than the light that reaches Earth, so the panels need to be big. They cover an area equal to 85m\u00b2, or about half the size of a volleyball court.<\/p>\n Its three-metre-diameter antenna will send the data JUICE collects back to mission control, although it will take almost two hours to travel the more than half a billion kilometres to Earth.<\/p>\n ESA had been working towards launching JUICE in 2022 until the coronavirus pandemic hit. Instead of the planned liftoff, this coming year will now see frantic activity as ESA scrambles to claw back the time lost during lockdown, and make the final preparations needed to ready the landmark mission for its rescheduled launch in 2023.<\/p>\n The original plan was for JUICE to take a convoluted route, involving five flybys of Earth, Venus and Mars to use the planets\u2019 gravitational might to slingshot the spacecraft towards Jupiter, a journey that was set to take 7.5 years. ESA has yet to reveal exact details of the new timeline, but JUICE should arrive at Jupiter at the start of the 2030s. Once there, it will spend at least three years exploring Europa, Ganymede and Callisto. It will be joined by NASA\u2019s Europa Clipper mission, currently scheduled for launch in 2024 and arrival in April 2030.<\/p>\n We\u2019ve known about these moons for a long time. Along with Io \u2013 the most volcanically active place in the Solar System \u2013 Europa, Ganymede and Callisto make up the so-called \u2018Galilean moons\u2019, first seen by the Italian astronomer Galileo at the start of the 17th Century.<\/p>\n Of the trio that JUICE will focus on, Europa tends to steal the limelight. \u201cIt\u2019s definitely the poster child of the Galilean moons,\u201d says Fox-Powell. That\u2019s because beneath its icy crust sits an ocean that contains more liquid water than all of Earth\u2019s seas, lakes and rivers combined. If there\u2019s life swimming around in our oceans, could the same be true of Europa?<\/p>\n Part of the problem is that the ocean is hiding beneath a thick, icy surface. \u201cWe can\u2019t access it directly,\u201d says Fox-Powell. Thankfully, scientists think the icy crust and the water are interacting, a bit like the molten rock beneath Earth\u2019s surface that breaks through during volcanic activity. \u201cIt means we can use material on the surface to study the oceans indirectly,\u201d Fox-Powell says.<\/p>\n We may even be able to collect a sample of that material, despite JUICE being unable to land on Europa. The spacecraft is carrying 10 high-precision instruments to Jupiter, including the Particle Environment Package (PEP)<\/a>. \u201cIt\u2019s designed to study dust and other molecules that have been kicked up from the surface,\u201d says Fox-Powell. \u201cIt\u2019s not impossible that, if that material came from the oceans, it could contain molecules that are indicative of life.\u201d<\/p>\n If there are organisms in Europa\u2019s oceans, then they\u2019ll need a source of energy. Hidden beneath the icy crust, they can\u2019t get that energy from the Sun. Fox-Powell sees two potential options. The Jovian system is an environment flooded with intense levels of radiation as Jupiter\u2019s magnetic field slings and funnels high-energy particles around.<\/p>\n \u201cAny ocean material that ends up on the surface is going to be irradiated,\u201d Fox-Powell says. That changes the chemistry of the ice. One likely scenario is that the radiation is breaking water into hydrogen and oxygen, with that oxygen potentially seeping back down into the ocean below. Other potential by-products include compounds containing the element sulphur. \u201cOn Earth, they\u2019re known to support microbial life,\u201d says Fox-Powell. JUICE will help us to learn more about that ocean-surface boundary and to what extent the conditions are suitable for biology.<\/p>\n Alternatively, life may have colonised the ocean floor. On Earth, there are whole communities of organisms that thrive on the seabed without any sunlight whatsoever. The source of their energy is hydrothermal vents \u2013 cracks in the boundary between the ocean and Earth\u2019s hot interior. JUICE could help us see how geologically active Europa\u2019s interior is.<\/p>\n While Europa grabs the lion\u2019s share of public attention, it\u2019s not JUICE\u2019s main target. The mission will only fly by Europa twice but will buzz past Callisto on 12 occasions. Callisto is the outermost of the four Galilean moons, so is least affected by Jupiter\u2019s gravity and radiation. In contrast to Europa, whose surface is constantly reshaped by material welling up from beneath the ice, Callisto has the oldest surface in the Solar System. Unchanged for billions of years, it\u2019s pockmarked by more impact craters than any other body orbiting the Sun.<\/p>\n Astronomers suspect that a 200km-deep ocean lies beneath Callisto\u2019s ancient surface. This is where JUICE\u2019s Radar for Icy Moons Exploration (RIME)<\/a> instrument will come into its own. It will transmit radio waves that can penetrate the icy shells of the Galilean moons down to a depth of around nine kilometres. From the way the radio waves are reflected back, we should be able to learn more about the moons\u2019 internal structures.<\/p>\n Another approach will be provided by the Gravity and Geophysics of Jupiter and Galilean Moons (3GM) instrument<\/a>. It will measure the gravitational fields of Callisto and the other icy moons, which will reveal how different layers of material \u2013 including water \u2013 are stacked up inside them.<\/p>\n JUICE will also use Callisto for a leg-up. Mission controllers will use the gravity of the moon to increase the spacecraft\u2019s inclination by about 30\u00b0 so it can get a better look at Jupiter\u2019s polar regions \u2013 the source of Jupiter\u2019s vast and intense magnetic field.<\/p>\n It is magnetism that determined where JUICE will spend the bulk of its time: Ganymede. Along with a dozen fly-bys, the spacecraft will also go into orbit around Ganymede and stay there for eight months. It will be the first time that a spacecraft from Earth has orbited a moon other than our own.<\/p>\n \u201cGanymede is the most exciting body in the Solar System,\u201d says Prof Michele Dougherty<\/a>, from Imperial College London. For one thing, it\u2019s bigger than any other moon. In fact, it\u2019s bigger than the dwarf planet Pluto and the planet Mercury. Like Europa, it\u2019s also thought to have a sub-surface ocean that contains more water than we have on Earth.<\/p>\n Yet it\u2019s Ganymede\u2019s magnetism that\u2019s the main attraction. It\u2019s unique among the moons of the Solar System for having a magnetic field of its own. Dougherty is the principal investigator for J-MAG<\/a> \u2013 an instrument on JUICE for measuring magnetic fields. J-MAG is located at the end of a 10.6m-long boom to keep it away from magnetic interference from the main spacecraft. Its sensitive electronics are locked inside a lead-lined vault to protect them from Jupiter\u2019s intense radiation.<\/p>\n Dougherty wants to measure Ganymede\u2019s magnetic field in detail, including how it interacts with Jupiter\u2019s own magnetic field. Astronomers using the Hubble Space Telescope<\/a> have spotted auroral activity on Ganymede. The equivalent of the northern and southern lights on Earth, the auroras should wobble around Ganymede\u2019s poles due to the influence of Jupiter\u2019s magnetism.<\/p>\n That they don\u2019t, suggests a sub-surface ocean of salty water on Ganymede that\u2019s conducting electricity and counter-balancing Jupiter\u2019s magnetic might. Studying Ganymede\u2019s magnetic field could provide further clues about the size and nature of this ocean. In turn, that could help us understand if it\u2019s a place that may be home to alien life.<\/p>\n Separating Ganymede\u2019s magnetic field from Jupiter\u2019s is far from straightforward, though, particularly given how much the planet dominates its surrounding satellites. \u201cIt\u2019s like trying to find needles in a haystack,\u201d Dougherty says, \u201cbut they\u2019re changing size, shape and colour all the time.\u201d Still, she\u2019s confident the team can pull it off. The flybys will be used to practise, with the really important data coming once JUICE settles into orbit around Ganymede. \u201cThe results are going to be spectacular,\u201d Dougherty says.<\/p>\n If she\u2019s right, it\u2019ll be the crowning achievement at the end of a long and winding road. Dougherty was previously involved in another flagship spacecraft: the Cassini mission<\/a> to Saturn. Discussions about JUICE began in earnest in 2008, when Cassini had already been at Saturn for four years.<\/p>\n It was one of Saturn\u2019s moons \u2013 Enceladus \u2013 that made people sit up and take notice. \u201cMy team was instrumental in discovering that Enceladus has plumes of water vapour,\u201d Dougherty says. Water from a sub-surface ocean was being spat out into space, showing that it\u2019s possible to find water beyond the traditional habitable zone.<\/p>\n \u201cThe discoveries at Enceladus showed us that focusing on moons of the outer planets was a good thing to do.\u201d Soon a plan was hatched to get a closer view of Jupiter\u2019s icy moons. Not that it\u2019s all been plain-sailing. At one point during the pandemic, with labs closed, Dougherty\u2019s team was building parts of J-MAG on their kitchen tables. \u201cBuilding an instrument is always stressful, but the pandemic took that stress to the next level,\u201d she says.<\/p>\n That effort is all the more remarkable given that the team will eventually destroy all of that hard work. Sometime in 2034, the spacecraft is likely to run out of propellant. Without any fuel, scientists will no longer be able to manoeuvre it around the Jovian system. So the team will do what\u2019s been done before with spacecraft like Cassini and the MESSENGER mission to Mercury: deliberately crash it.<\/p>\n By smacking into the surface of Ganymede, JUICE will provide one final experiment to see what this gargantuan moon is made of. Its days of exploring Jupiter\u2019s icy moons will be over, but scientists will continue to pore over JUICE\u2019s collection of valuable data for a long time afterwards. \u201cIn 20 years\u2019 time, our understanding of these moons will be different,\u201d says Fox-Powell. \u201cJUICE is going to provide a real revolution.\u201d It could, finally, tell us whether or not we\u2019re alone in this vast and often surprising Solar System.<\/p>\n Read more about the future of space exploration:<\/strong><\/p>\n By Colin Stuart Published: Thursday, 27 January 2022 at 12:00 am Deep beneath the salty ocean, the seafloor is cracked. Hot gases from the layers below bubble into the water, sustaining colonies of microbial life that are eking out an existence far from the sunkissed surface. This may sound like a scene from the bottom […]<\/p>\n","protected":false},"author":24,"featured_media":5756,"template":"","categories":[1],"acf":{"readingTimeMinutes":"11"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons.jpg",1200,511,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons-300x128.jpg",300,128,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons-768x327.jpg",768,327,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons-1024x436.jpg",800,341,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons.jpg",1200,511,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/42\/2022\/01\/juice-what-secrets-lie-beneath-the-icy-surface-of-jupiters-moons.jpg",1200,511,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"By Colin Stuart Published: Thursday, 27 January 2022 at 12:00 am Deep beneath the salty ocean, the seafloor is cracked. Hot gases from the layers below bubble into the water, sustaining colonies of microbial life that are eking out an existence far from the sunkissed surface. This may sound like a scene from the bottom…","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/rss_feed\/5755"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/media\/5756"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/media?parent=5755"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/wp-json\/wp\/v2\/categories?post=5755"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\""An\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/4\/2022\/01\/Image-of-Europas-surface-taken-by-the-Galileo-spacecraft-b49d863.jpg?quality=90&resize=620%2C626"\" "\\"\"Galileo\\"")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>The spacecraft<\/h2>\n
![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/4\/2022\/01\/Scale-model-of-the-RIME-antenna-at-the-Hertz-facility-Netherlands-3f2d07a.jpg?quality=90&resize=620%2C413"\" "\\"\"Scale\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>The moons of Jupiter<\/h2>\n
![\""Ice\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/4\/2022\/01\/Artists-impression-of-ice-volcanoes-on-Europa-b80e953.jpg?quality=90&resize=620%2C465"\" "\\"\"Ice\\"")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>An opportunity to survey Callisto<\/h2>\n
Looking for magnetic fields<\/h2>\n
![\""Auroral\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/4\/2022\/01\/Image-showing-aurora-belt-around-Jupiter-taken-by-Hubble-3c735b0.jpg?quality=90&resize=620%2C519"\" "\\"\"Image\\"")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Is there life elsewhere in the Solar System?<\/h2>\n
![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/4\/2022\/01\/Simplified-mock-up-of-the-JUICE-spacecraft-3876cc2.jpg?quality=90&resize=620%2C413"\" "\\"\"Simplified\\"\/")
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