The exploration of the outer Solar System has revealed a plethora of amazing worlds, the likes of which were little known or even unheard of just a decade ago. Among the most remarkable and tantalizing discoveries are the “ocean moons” such as Europa and Enceladus, which have oceans or seas of liquid water beneath their icy surfaces. Other moons like Titan, Ganymede, and Callisto may also have them, and even some asteroids. Titan also has seas and lakes of liquid methane/ethane on its surface. With all that water, these small worlds have become a primary focus in the search for possible life elsewhere in the Solar System. Now, a new NASA budget proposal wants to take that a step further and fund new missions to these watery moons.
The water vapour geysers on Saturn’s moon Enceladus are one of the most fascinating phenomena in the Solar System; the jets spray far out into space in a dazzling display unseen anywhere else. Known to emanate from the “tiger stripe” fissures at the south pole, they were thought to be separate, distinct plumes erupting from the surface, but now scientists think that they might actually be mostly broader, more diffuse “curtains” of spray along the length of the fissures.
The deep oceans on Earth are teeming with life, despite the cold and darkness, thanks to hydrothermal vents which provide needed heat and nutrients in an otherwise rather uncomfortable environment. Now, the first evidence has been found for current hydrothermal activity elsewhere in the Solar System: on the ocean bottom of Saturn’s moon Enceladus.
Along with Jupiter’s infamous moon Europa, Saturn’s moon Enceladus is one of the most fascinating places in the Solar System, with its huge geysers of water vapour erupting from cracks in the surface at the south pole. The massive plumes are now thought to originate in a subsurface ocean or sea of salty liquid water, similar perhaps to Europa’s underground ocean. Now, new analysis is providing a more detailed look at the chemical makeup of this unique alien environment and its potential to support life.
Europa has intrigued people for decades, ever since the first evidence was found that this small icy moon of Jupiter harbours a subsurface ocean. Additional information about the actual conditions below the surface have been difficult to obtain, since this ocean is covered by a global crust of ice perhaps ten of kilometres thick in places. But perseverance pays off, and now in just this past week there are two new significant discoveries being talked about – evidence from the Hubble Space Telescope for water vapour plumes, announced on Thursday, erupting from Europa’s surface similar to those on Saturn’s moon Enceladus, and the first detection of clay-type minerals on the surface, announced on Wednesday.
Not all that long ago, it was considered very unlikely that life could exist anywhere else in the solar system, apart from maybe Mars. A variety of robotic spacecraft missions, however, have changed scientists’ views; there are indeed a handful of other worlds in our own cosmic backyard which it is now known could potentially be habitable after all.