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NASA says new observations from the Hubble Space Telescope confirm the presence of a subsurface ocean on Jupiter's largest moon.
This artist's concept shows Ganymede in the shadow of Jupiter, with its aurorae glowing. NASA/ESA
NASA says new observations from the Hubble Space Telescope confirm the existence of a salty subsurface ocean on Ganymede, the largest moon in the solar system, which orbits our largest neighbor planet, Jupiter. The ocean is estimated to be about 60 miles thick -- 10 times deeper than the Mariana Trench, the deepest part of the Pacific -- but is buried under a layer of mostly icy crust 95 miles thick. Ganymede joins other neighborhood moons like Europa, the asteroid belt dwarf planet Ceres, and Saturn's Enceladus and Titan that host strange icy or liquid layers, making them prime targets in the search for life beyond Earth. Scientists have hypothesized for decades that Ganymede might harbor an icy or even liquid ocean beneath its frigid surface. The key to confirming the presence of a saltwater ocean came from observing Ganymede's aurorae, which would look bright red to a human able to stand on the surface of the moon and gaze up through its thin oxygen atmosphere. But don't get too excited, it's much too thin to support life as we know it.
Auroral phenomena -- think the bright northern lights of the aurora borealis or the aurora australis down south -- are not fully understood, but are linked to magnetic fields interacting with the solar wind. Ganymede is the only moon in the solar system that generates its own magnetic field thanks to its liquid iron core, but it also lies within the magnetic field of massive Jupiter. As Jupiter's magnetic field changes, it affects the aurorae on Ganymede, causing them to "rock back and forth" according to Joachim Saur, a professor for geophysics at the University of Cologne, who presented the news on a NASA teleconference Thursday.
Saur explained that the rocking effect seemed to be dampened by something else. Rather than altering the aurorae six degrees, as models suggested that they should given the electromagnetic fields involved, they only changed by two degrees, leading scientists to conclude that the rocking is inhibited by a salty subsurface ocean. "This confirms the existence of an ocean and simultaneously rules out the absence of an ocean," he told reporters. The news comes on the heels of the finding earlier this week that Saturn's moon Enceladus may contain enough warm water to support life. Ganymede will also now be more competitive when it comes to garnering attention among the Jovian moons -- its sibling Europa and its presumed subsurface ocean has long excited space geeks, even working its way into the priority list for future NASA missions. Looks like NASA may now need to add another moon to its itinerary for that deep-space journey.
Moscow (AFP) - Russian scientists have now discovered seven giant craters in remote Siberia, a geologist told AFP on Thursday, adding that the mysterious phenomenon was believed to be linked to climate change.
The discovery of an enormous chasm in a far northern region known to locals as "the end of the world" in July last year prompted speculation it had been caused by a meteorite or even aliens.
A YouTube video of the hole went viral and a group of scientists was despatched to investigate.
"We have just learnt that in Yakutia, new information has emerged about a giant crater one kilometre (0.6 miles) in diameter," the deputy director of the Oil and Gas Research Institute of the Russian Academy of Sciences, Vasily Bogoyavlensky, told AFP.
He said this brought to seven the number of reported pits.
"Footage allows us to identify minimum seven craters, but in fact there are plenty more," he said.
All of the craters have been discovered in the remote energy-rich Yamalo-Nenetsky region in north-western Siberia.
Scientists say that rather than aliens or meteorites, the holes are caused by the melting of underground ice in the permafrost, which has possibly been sped up by rising temperatures due to global warming.
"The phenomenon is similar to the eruption of a volcano," said Bogoyavlensky.
As the ice melts, methane gas is released which builds up pressure until an explosion takes place, leading to the formation of a crater.
The scientists are still trying to estimate what danger, if any, is posed by the holes. Methane is extremely flammable and at least one of the craters is situated near an exploited gas deposit.
An expedition is planned to the latest crater discovered to determine if it was formed in the same manner.
It may be hard to identify other craters which may have formed into lakes over time, said Bogoyavlensky.
"When they appear the craters are empty, and little by little they fill up with water. In the space of two or three years they become lakes and it is difficult to study them."
He said some may have formed dozens or hundreds of years ago, but went unnoticed in such remote regions of the planet.