After last December's announcement that the Hubble Space Telescope spotted what may be water geysers erupting from Jupiter's icy moon Europa, it may be time for us to refocus our search for life on other bodies in the solar system.
While NASA's Curiosity rover drives around on Mars, wowing us with incredible discoveries about what the planet was like in the past and how it could have supported life, the chances of the rolling robotic science lab actually discovering life on the Red Planet now is fairly remote. That's not to say that Mars is dead, but with the conditions there, any forms of life that actually do still exist on the planet are likely underground, far beyond Curiosity's reach. Another Mars rover is being planned for a 2020 launch, which is meant to follow up on Curiosity's finds by actually looking for signs of past life. However, while exploring Mars is still a worthwhile effort, as it leads to insights about our own past and provides us with clues about how we can live there in the future, our search for life that currently exists on the other planets and moons of our solar system is going to have to concentrate elsewhere.
From what science writer Michael Hanlon wrote in The Telegraph earlier this week, we already have somewhere else to look:
Water is a perfect solvent (just about everything, even gold, dissolves in water to some extent), allowing the complex suite of biochemical reactions that drive living processes. Other liquids have been proposed as the basis of life, but most biologists believe that water-plus-carbon is the most likely scenario for life outside Earth.
The trouble is, liquid water is a rare commodity in the Solar System. Frozen water is everywhere. Comets are mostly made of water ice. Mars is covered with the stuff. The outer planets and their moons are rich in water. But large quantities of the liquid stuff are rare.
Which is why scientists are so excited about Europa, the second of Jupiter’s large Galilean moons, which has just become the new hot destination in the solar system.
Ever since it was first discovered that Jupiter's moon Europa is completely covered in ice, there's been speculation about what may lie under that icy crust. Due to a combination of Jupiter's gravity and the interaction with Jupiter's other moons, the rocky core of Europa is regularly squeezed and flexed, creating what's called 'tidal heating.' The effects of this squeezing and heating are obvious on the surface of Europa's ice, from the immense cracks that line and crease its face in our iconic photographs. However, the sub-surface effects would be much more important, and scientists are confident that there's an ocean of liquid water under all that ice. Not only that, but since Galileo found that Europa's magnetic field fluctuates, that's a strong indication that the ocean is made up of salt water.
Also, scientists recently looked back through data gathered by NASA's Galileo spacecraft, over 15 years ago, and they spotted what looks to be clay-like minerals in Europa's surface ice. Since these minerals surround an impact crater, from either an asteroid or a comet, and these objects typically carry organic compounds on them, that impact may have added the third component for life to develop (if it wasn't there already).
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This puts us back in the same situation as we have on Mars, though, where the life we want to detect is far under the surface we're able to explore. However, if what Hubble spotted actually was a plume of water vapour shooting up from Europa's south polar region, it actually gives us a way past that particular problem. If these plumes are squeezed up through the ice directly from the ocean, and more of these plumes shoot out all the time, a probe could just sample the water vapour to look for signs of life. That makes Europa the best place to focus our search next, and according to Hanlon, when it comes to the call for a mission to be sent there, Kevin Hand, an astrobiologist at NASA's Jet Propulsion Laboratory says that "the drumbeat is getting louder."
The next mission to arrive at Jupiter is NASA's Juno spacecraft, which is set to arrive there in July 2016. Juno isn't going there to investigate Europa though. That will take a new mission. NASA's Europa Clipper may never happen or it may be several years before it can launch, but according to New Scientist, Ben Longmier and his team at the University of Michigan's Aerospace Engineering Department are working with NASA to develop thrusters and sensors for tiny CubeSats that could reach Europa in the next three to five years.
(Image courtesy: NASA/JPL-Caltech)
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