In the course of this week two different findings concerning Europa, one of the largest satellites of Jupiter, have been announced. They are the results of two completely separate research that by chance were published almost simultaneously. Another coincidence is that both findings are connected to a possibility that there are life forms on Europa.
The first announcement concerns the discovery of clay-like minerals on the surface of Europa, specifically phyllosilicates. They seem to have arrived on this satellite because of a collision with an asteroid or a comet. Not by chance it’s the first time that this kind of minerals have been detected on the surface of Europa.
This discovery is the result of a new analysis of very old data. In fact, those are infrared images taken by the Galileo space probe. It reached Jupiter’ orbit in December 1995 and its mission ended in September 2003, when it was deliberately thrown into Jupiter’s atmosphere at high speed to destroy it.
The pictures studied by Jim Shirley of NASA’s Jet Propulsion Laboratory go back to 1998 and have a low quality by today’s standards. During these years new techniques to improve the quality of the images have been invented and they’ve been applied to those of Europa taken by the Galileo spacecraft. The result was the discovery of the phyllosilicate in an area that has the shape of a broken ring about 40 km (25 miles) wide approximately 120 km (75 miles) away from the center of a crater with a diameter of about 30 km (20 miles).
The best explanation for the presence of those materials is that an asteroid or a comet crashed on Europa. This type of clay-like materials are typical of space rocks that also contain organic materials. The diffusion of organic materials in the oceans of liquid water existing beneath Europa’s icy surface may have contributed to the emergence of life forms.
Another very interesting finding was made using the Hubble Space Telescope instead. Thanks to spectroscopic observations of Europa’s southern polar region, they detected emissions of hydrogen and oxygen with characteristics that show that these elements are derived from water molecules broken by Jupiter’s strong magnetic field.
In essence, there are strong indications that from the south pole of Europa plumes of water vapor erupt. Geyser of this type have been identified on Enceladus, a moon of Saturn, by the Cassini space probe. The Hubble Space Telescope is too far away to provide images of the same quality as Cassini’s but the analysis suggests that the two phenomena are very similar.
The difference is that the steam emitted by the geysers on Enceladus gets lost in space due to the very limited gravity of this satellite while that emitted by Europa rises to a height of about 200 km (125 miles) but then gravity is strong enough to make it fall back to the surface.
These plumes were detected in December 2012, when Europa was at its apocenter, which is the position farthest from Jupiter. This allows us to better understand the activity that takes place beneath the surface of Europa, caused by the gravitational stress created by its continuous movement towards and away from Jupiter.
The existence of this phenomenon confirms once again that beneath the surface of Europa a huge amount of thermal energy is emitted. There may be even volcanoes which are invisible from Earth, unlike the existing ones on Io, another satellite of Jupiter. This could also cause various types of minerals spreading in liquid water, an essential factor for the development of life forms.
There were already clues about the fact that on Europa there could be something similar to the so-called primordial soup that led to the origin of life on Earth. Over the years there have been several proposals for space missions to Europa exactly to see what’s going on in its oceans. Unfortunately, so far the budgets of the various space agencies haven’t allowed to approve even one of them so the observations will go on from a distance.