{"id":16475,"date":"2015-03-13T22:05:29","date_gmt":"2015-03-13T14:05:29","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/hubble-observations-reveal-ocean-on-ganymede\/"},"modified":"2015-03-13T22:05:29","modified_gmt":"2015-03-13T14:05:29","slug":"hubble-observations-reveal-ocean-on-ganymede","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/hubble-observations-reveal-ocean-on-ganymede\/","title":{"rendered":"Hubble observations reveal ocean on Ganymede"},"content":{"rendered":"
\"In
In this artist\u2019s concept, the moon Ganymede orbits the giant planet Jupiter. NASA\u2019s Hubble Space Telescope observed aurorae on the moon controlled by Ganymede\u2019s magnetic fields. This field is embedded in Jupiter\u2019s own immense magnetosphere (yellow field lines). A saline ocean under the moon\u2019s icy crust reduces shifting in the auroral belts as measured by Hubble. Credit: NASA\/ESA<\/figcaption><\/figure>\n

Scientists using the Hubble Space Telescope have found the best evidence yet of a salty ocean of liquid water lurking beneath the surface of Jupiter\u2019s largest moon Ganymede, ripening the icy world\u2019s allure as mission planners design probes for more detailed exploration.<\/p>\n

Long thought to possess an underground ocean, Ganymede is the largest moon in the solar system and measures bigger than Mercury.<\/p>\n

Researchers studied the oscillation of auroral belts near Ganymede\u2019s north and south poles with Hubble to conclude a substantial reservoir of liquid water must exist beneath the moon\u2019s icy crust.<\/p>\n

\u201cOur new HST observations provide the best evidence to date for the existence of an ocean on Ganymede,\u201d said Joachim Saur, professor of geophysics at the University of Cologne in Germany.<\/p>\n

Ganymede is the only only moon in the solar system with its own magnetic field, triggering belts of polar aurorae similar to the northern and southern lights on Earth.<\/p>\n

\u201cIf someone could be standing on Ganymede looking up into the night sky, it would appear as red aurora to you, and it would be visible even with the naked eye,\u201d Saur said Thursday in a teleconference with reporters.<\/p>\n

The magnetic field of Ganymede also interacts with Jupiter\u2019s powerful magnetism, causing the belts to shift in latitude. Saur\u2019s science team won prized observing time with Hubble to measure how much the auroral belts oscillate over time.<\/p>\n

\u201cThis is a really great example of using a remote sensing technique \u2014 using a telescope in orbit around the Earth \u2014 to study a moon that\u2019s in orbit around Jupiter and yet be able to make inferences about the interior of that moon just by looking at it from the outside,\u201d said Heidi Hammel, executive vice president of the Association of Universities for Research in Astronomy. \u201cWe aren\u2019t at Jupiter. Hubble is at the Earth, and yet it can probe the internal structure of this moon remotely. That\u2019s a really powerful tool.\u201d<\/p>\n

It turns out the volume of water persisting beneath Ganymede\u2019s surface has an influence on the aurorae, counteracting the tug from Jupiter that would cause the belts to \u201crock\u201d up to 6 degrees back and forth every 10 hours.<\/p>\n

\u201cHowever, when there is a salty, and thus electrically-conducting ocean present, this ocean counterbalances Jupiter\u2019s magnetic field influence and reduces the rocking of the aurora to only 2 degrees,\u201d Saur said.<\/p>\n

\"NASA
NASA Hubble Space Telescope images of Ganymede\u2019s auroral belts (colored blue in this illustration) are overlaid on a Galileo orbiter image of the moon. The amount of rocking of the moon\u2019s magnetic field provided evidence that the moon has a subsurface saltwater ocean. Credit: NASA\/ESA<\/figcaption><\/figure>\n

\u201cWe used HST (and) looked at Ganymede for more than five hours, and monitored the aurorae and saw that the aurorae barely moved during that five hours \u2014 only rocking by 2 degrees \u2014 exactly like (we) predicted when there is an ocean present,\u201d Saur said. \u201cThis confirms the existence of an ocean and simultaneously it rules out the absence of an ocean.\u201d<\/p>\n

Scientists believe Ganymede\u2019s buried ocean has more water than all the water on Earth\u2019s surface, perhaps measuring as much as 60 miles thick underneath a 95-mile crust of mostly ice, according to a NASA press release.<\/p>\n

\u201cThis discovery marks a significant milestone, highlighting what only Hubble can accomplish,\u201d said John Grunsfeld, associate administrator of NASA\u2019s science mission directorate. \u201cIn its 25 years in orbit, Hubble has made many scientific discoveries in our own solar system. A deep ocean under the icy crust of Ganymede opens up further exciting possibilities for life beyond Earth.\u201d<\/p>\n

According to Saur, the team based in Cologne used Hubble on two occasions in 2010 and 2011 to monitor the movement of aurorae in ultraviolet light, simultaneously observing Ganymede\u2019s northern and southern belts.<\/p>\n

\u201cWe have four independent measurements, and all four measurements show that the aurorae in all these cases moved by 2 degrees only, and this gives us confidence in the measurement,\u201d Saur said.<\/p>\n

NASA will celebrate the 25th anniversary of Hubble\u2019s launch in April, and officials are confident the storied observatory will continue operating into the 2020s after repairs by astronauts on a series of space shuttle missions, most recently in 2009.<\/p>\n

\u201cHubble is the only observatory right now that can do these kind of observations in ultraviolet light, and be able to precisely resolve and disinctly detect these features on Ganymede,\u201d said Jennifer Wiseman, NASA Hubble senior project scientist.<\/p>\n

NASA\u2019s Galileo spacecraft orbited Jupiter from 1995 to 2003, flying by the giant planet\u2019s moons to snap photos, study their geology and measure their composition. Galileo conducted six flybys of Ganymede, finding evidence that part of the moon\u2019s surface had been flooded from water eruptions through ice volcanoes.<\/p>\n

\u201cBased on the geology, we believe there was a time when the ocean may have communicated with the surface in the distant past,\u201d said Jim Green, director of NASA\u2019s planetary science division.<\/p>\n

\u201cSince the 1970s, there was speculation and models that Ganymede could possess an ocean,\u201d Saur said. \u201cHowever, there was only one (piece of) observational evidence, and that comes from the Galileo orbiter. Galileo had six close flybys of Ganymede, but these flybys lasted only 20 minutes each. That\u2019s too short to resolve the effects of the ocean without ambiguity \u2026 The new trick with the Hubble observation is that we have seven hours of data, and then we do not have this ambiguity any more.\u201d<\/p>\n

\"Artist's
Artist\u2019s concept of ESA\u2019s JUICE spacecraft. Credit: ESA<\/figcaption><\/figure>\n

The European Space Agency plans to launch a probe to Jupiter in June 2022 for the most in-depth study of Ganymede yet.<\/p>\n

Arriving at the gas giant in January 2030, the Jupiter Icy Moons Explorer will zip past Jupiter\u2019s moons Europa and Callisto, each believed to contain subterranean oceans, multiple times before settling into orbit around Ganymede for nearly 10 months.<\/p>\n

NASA is working on a separate mission for launch in the 2020s to focus on Europa, and the space agencies could partner to build instruments and secondary payloads to accompany each spacecraft on the journey.<\/p>\n

ESA\u2019s JUICE mission and NASA\u2019s Europa flyby probe \u2014 successors to the Galileo orbiter \u2014 could be flying through the Jupiter system at the same time in the 2030s.<\/p>\n

\u201cWhen the JUICE mission ultimately goes into orbit around Ganymede, it will have a very, very rich and exciting science mission,\u201d Hammel said.<\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/i><\/b><\/p>\n","protected":false},"excerpt":{"rendered":"

In this artist\u2019s concept, the moon Ganymede orbits the giant planet Jupiter. NASA\u2019s Hubble Space Telescope observed aurorae on the moon controlled by Ganymede\u2019s magnetic fields. This field is embedded in Jupiter\u2019s own immense magnetosphere (yellow field lines). A saline ocean under the moon\u2019s icy crust reduces shifting in the auroral belts as measured by […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1660,1605,1606],"class_list":["post-16475","post","type-post","status-publish","format-standard","hentry","category-news","tag-ganymede","tag-juice","tag-jupiter"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/16475"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=16475"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/16475\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=16475"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=16475"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=16475"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}