Life in space might actually be closer than we have thought so far. Not in the depth of the universe, where the Kepler stars are presumably orbited by habitable planets. But right here with us, in the inhospitable environment of Saturn's moon Enceladus.
This moon is relatively small. With only 500 km in diameter it wouldn't even fill out Germany. It's surface is barely as big as France and the UK combined. It is entirely coated with ice and on it's surface the temperature is about -200° C.
But this moon has one distinctive feature. In the South Pole region there are warm areas strong enough to melt the water under the surface. A subterranean ocean, whose water regularly spouts like gush springs into space through long cracks in the surface, the so called tiger cracks. This kryovolcanic activity provides the E-ring of Saturn with material. In 2008, the space probe Cassini was able to fly exactly through one of those gushes in a dangerously close fly by of only 23 kilometers and analyzed its chemical components. And voila: Enceladus fulfills some of the most important criteria for life: warmth, liquid water and organic chemicals.
There are eight planets in our solar system. Actually, it used to be nine until it turned out that Pluto was part of of an asteroid belt. In this belt there are hundreds of other objects the size of Pluto. Giving all of them the status of planets seemed disproportionate. For convenience, the ninth planet just lost its status. And now we have eight.
Saturn, the planet which is orbited by Enceladus, is approximately in the middle between the outermost planet (Neptun) and the Sun. Enceladus orbits around Saturn slightly outside the clearly visible ring in the unseeming E-ring, also called the Enceladus-Ring. Enceladus provides it with material like ice.
In order to examine Saturn and its moon in more detail, the Cassini-Huygen probe was sent on its long journey at the end of the last century. In 2008, the probe flew through a gush spring eruption of Enceladus. It could then measure what is being shot into the E-Ring.
It turned out that, on Encelauds, like on Europa and Titan for instance, there are good conditions for life. In the extraterrestrial ocean under the ice surface of Enceladus one could suspect an environment in which specialized life forms might have developed.
Finding out more requires a landing on the moon. With the right equipment.
The hidden, subterranean - or better sub-Enceladian - ocean leaves room for speculation. could there, in the waters of the Saturn moon, be organic life? Bacteria that withstand those temperatures?
Or has more developed in the course of the millennia? Simple life forms that have, in the darkness of the subterranean ocean, adapted to the inhospitable environment?
Since the ecosystem of Eceladus is rather simple in terms of complexity, it seems likely that the life forms would not be very big. You would probably not find a whale there.
A number of simple species could nevertheless have developed. Also, at the warmer bottom of the ocean a simple flora would be in the realm of possibility, marking the beginning of the food chain.
To follow up on these hypotheses, science would need a robust space probe, that would, first of all, survive the trip to Enceladus and would, secondly, after a rough landing be able to do some drilling into the ice to then descent into the water to explore.
Here on earth, all this is already possible. But an expedition into the unexplored realms of space is still a great research challenge. We remain on our toes!
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