Until relatively recently, it was thought that the best, or perhaps only, place to look for life elsewhere in the solar system was Mars. The other inner planets were much too hot while the outer gas and ice giants were far too cold – the chances of any kind of life being found, even microbes, was considered extremely unlikely at best.
Jupiter’s moon Europa has long been regarded as one of the most likely places in the solar system where some form of life could exist outside of Earth. Evidence from visiting spacecraft has shown that it almost certainly has a liquid water ocean beneath its icy surface. That water is also thought to be similar to that in Earth’s salty oceans and rich in oxygen.
Obtaining any answers to the life question however will require further missions to be sent there, and that is the tricky part. The costs involved have pushed back such missions; the current mission proposal, the Europa Jupiter System Mission, would launch sometime within this decade. Europe would then follow with its own mission to Ganymede, another Jupiter moon thought to have a subsurface ocean.
Jupiter’s moon Europa is one of the most intriguing places in the solar system – with a global ocean of water thought to exist beneath its ice crust, speculation has grown that it may harbour life of some kind.
Studies have shown the water is likely quite similar to ocean water on Earth, with abundant oxygen available. If there are heat sources like hydrothermal vents, as on Earth, and chemical nutrients, the Europan ocean would seem an ideal place to search for life of some kind. Even with no sunlight due to the perpetual ice cover, life could still thrive; various organisms and marine life have been found here on Earth, in similar environments below the ice of Antarctica for example.
According to the report, oxygen in Europa’s crust, formed by bombardment from cosmic radiation, reacts with sulphur and other material coming from rocks at the bottom of the ocean, creating sulfuric acid. The scientists involved used the same computer models used to predict the chemistry of groundwater or the chemistry of water at phosphate mines here on Earth.
As explained by Assistant Professor of Geology Matthew Pasek at the University of South Florida, “When the two meet, they generate acid – sulfuric acid in this case. That would produce water with a pH of about 2.6, about the same as your average soft drink. Just as soft drinks are bad for your teeth as they are quite acidic, fish, corals, whales, or other large animals would find it difficult to live within the ocean of Europa.”
If true, it would make the environment more challenging for life to have started or evolved beyond simple microorganisms. Does it mean life would be impossible there? No, as there are microbes on Earth which do just fine in similar and even more extreme conditions, like the acid mines of Rio Tinto. The microbes actually use the iron and sulfide as energy sources. There is also the fascinating ecosystem, in dark subterranean caves in Mexico, where a wide variety of life forms, including small fish, also thrive in highly acidic conditions.
We will probably have to wait for a return mission to Europa before the life question can be addressed more directly. Until then, the debate will certainly continue.
All these worlds are yours except Europa Attempt no landing there Use them together use them in peace
Despite that famous cryptic warning in the film 2010: The Year We Make Contact, NASA is planning for a possible attempted landing on Jupiter’s moon Europa. This is a mission that many people have been hoping for, since Europa is believed to have a liquid water ocean beneath the icy surface (as well as lakes within the surface crust itself), making it a prime location in the search for life elsewhere in the solar system. Two landers are being proposed which would launch in 2020 and land about six years later…
Jupiter’s moon Europa has long been known as an ocean world, where evidence has continued to indicate that there is a global ocean of liquid water deep below the surface shell of ice. The environment is thought to be similar to ice-covered seas and oceans at the poles on Earth. But now there is also new evidence for lakes on Europa, which are inside the ice crust itself, between the surface and the ocean below. The lakes are thought to be about equal in volume to the Great Lakes in North America.
The data actually comes from a previous mission to Jupiter, Galileo, which provided scientists with decades worth of information to analyze about Jupiter and its moons.
With a deep ocean, Europa has become a prime candidate in the search for life elsewhere in the solar system. The question of habitability though, depends to some degree on how thick the ice shell is. If too thick, it would be difficult for organic nutrients and energy to be transferred between the surface and the ocean below. If thinner though, then it would be much easier, making life more plausible. The answer now seems to be a sort of compromise; the ice shell is thick in most places, but in some areas, known as “chaos terrain,” it is thinner, where it overlies the lakes.
According to Britney Schmidt, lead author of the paper and postdoctoral fellow at the Institute for Geophysics, University of Texas at Austin, “One opinion in the scientific community has been if the ice shell is thick, that’s bad for biology. That might mean the surface isn’t communicating with the underlying ocean. Now, we see evidence that it’s a thick ice shell that can mix vigorously and new evidence for giant shallow lakes. That could make Europa and its ocean more habitable.”
Until fairly recently, the search for life elsewhere in the solar system has focused primarily on Mars, as it is the most Earth-like of all the other planets in the solar system. The possibility of finding any kind of life farther out in the outer solar system was considered very unlikely at best; too cold, too little sunlight, no solid surfaces on the gas giants and no atmospheres to speak of on any of the moons apart from Titan…
Another great image on the Astronomy Picture of the Day web site, this one of Jupiter’s moon Europa, taken by the previous Galileo spacecraft mission. Evidence has continued to accumulate that under its relatively thin surface ice shell, there is a global ocean of liquid water, making Europa a prime target of proposed future missions to search for evidence of possible life…