Tuesday, 22 May, 2018

Europa's plumes make Jupiter moon a prime candidate for life

Yes, Europa really is sending plumes of water into space Europa is venting water into space, old spacecraft data suggest
Sandy Nunez | 15 May, 2018, 22:22

When NASA first announced it was going to Europa, it said that there are three objectives from the potential mission: to discover whether there is, or has ever been, life on Europa, to assess whether the celestial body is habitable, and to analyse the surface of the moon for future missions. Drawing on what scientists learned from exploring plumes on Saturn's moon Enceladus - that material in plumes becomes ionized and leaves a characteristic blip in the magnetic field - they knew what to look for.

Back in 2014, the Hubble Space Telescope captured something astonishing on Europa, one of Jupiter's biggest moons: a massive geyser-like plume that appeared to spurt from the moon's icy crust.

Galileo was passing some 200 kilometres above Europa's surface when it apparently flew through the plume. A plume venting some of Europa's ocean water into space where it could be sampled by an orbiting spacecraft would change the whole equation-it seemed, in short, too good to be true.

"The data were there, but we needed sophisticated modeling to make sense of the observation", said study lead author Dr. Xianzhe Jia, a space physicist at the University of MI. Computer simulations created by Xianzhe Jia, a space scientist at the University of MI, showed that a 120-mile-high geyser erupting from a relatively warm patch on Europa would create precisely the same readings. "This is very likely to be the result of a plume, making it the best direct evidence for such an occurrence yet". It may be that the region is either geologically active or the surface ice is thin or even broken, and this would allow plumes to erupt. She worries that instead, the Europa plume may be gushing out from an isolated underground lake, or even just a patch of surface ice evaporating away. There was a fair amount of suspicion of plumes from Europa's surface, but there was no hard evidence to back it up.

Europa's frozen surface has always been thought to cover a salty ocean about twice the size of our planet's. Back in 1997, it's nearly as if researchers didn't know to look for plumes of this sort - or simply did not expect such things. So Jia, Kivelson and their colleagues ran the data through a sophisticated modeling program that compared the observations with what scientists might expect to see from a plume of the dimensions reported by Hubble. The new paper essentially confirms that, finding that in 1997, a now-retired spacecraft flew through a jet of liquid that upset the magnetic field and plasma around the moon. In fact, according to NASA, if the plumes are indeed spewing from the moon, the orbiter might sample frozen liquid as well as dust particles. NASA's Europa Clipper spacecraft, now scheduled to launch in 2022, is created to fly closer than we've ever gotten to the Jovian moon. That makes it one of the most enticing worlds in our solar system where life could be hiding. During this encounter, scientists noticed a sudden drop in Europa's magnetic field at a spot above the equator.

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Fortunately for Europa fans, the moon is the destination of two planned missions.

Many experts believe the hidden ocean surrounding Europa, warmed by powerful tidal forces caused by Jupiter's gravity, may have conditions favourable for life.

From its orbit of Jupiter, Europa Clipper will sail close by the moon in rapid, low-altitude flybys, it said.

If it finds a plume, Clipper's instruments will be able measure its chemical composition, said Elizabeth Turtle, a planetary scientist at the Johns Hopkins Applied Physics Laboratory and one of the primary researchers involved with the mission.