If life is found on Europa, it would hold immense implications for the future of space exploration and, for that matter, of many other aspects of human life. In particular, finding life on Europa, even primitive micro-organisms (which is most likely what would be found) would be strong evidence that life can either develop or be seeded in a wide range of environments, including some well outside the theoretical “habitability” zone of stars, where Earth is said to be located. Thus far no probe capable of searching for life on this watery moon of Jupiter has ever been launched, although concept vehicles do exist which could lead to a working probe in the future.
Europa is one of the four large Galilean moons of Jupiter. Uniquely, however, it is a water world, at least underneath its pockmarked icy surface. It has an iron core, a thin oxygen atmosphere, and, underneath its thick ice surface, a massive ocean of water. It is this ocean which has gained Europa the most attention in recent years. Along with Enceladus, which has a smaller underground ocean, and Titan, which has a methane-rich atmosphere, Europa is currently regarded as one of the likeliest candidates for extra-terrestrial life. This life would take the form of aquatic creatures, almost certainly on the micro-organism level rather than the rich diversity of large species which populate our own species. Most likely it would superficially resemble the extremophile life forms which populate the deepest and most hostile regions in the ocean, like deep-sea vents.
Thus far there has been no actual confirmation of the nature of Europa’s interior, because it has only been studied from Jupiter orbit. However, in recent years Europa seems to have moved ahead of Titan as the probable target for an upcoming probe mission jointly financed by NASA and the European Space Agency, to be launched in a decade or so. Eventually, we might build and send a submarine to Europa, as part of a space probe and lander package capable of making a landing on Europa’s surface, melting a path through the ice (drilling would probably be too complex and difficult), and then conducting a brief exploration of the oceans which lie below. However, the current plans for the NASA-ESA probe are for an orbiter only, which would study Europa as well as several other Jovian moons. For the moment, therefore, any discussion of life being found on Europa remains purely theoretical.
Still, Europa is one of the likeliest candidates in the solar system today, and if life is found on Europa, the implications would be immense. On an immediate level, it would salvage the space program, which has never really covered from the end of the Cold War and the end of the Space Race. The recent spate of probes sent to Mars has been motivated almost entirely by the discovery that surface water is and has been present on that planet and could be an indication of Martian life having existed in the past. The actual discovery of life on Europa would make space exploration an urgent national priority again.
On a more significant level, if life is found on Europa, even if it is only in primitive and microbiotic form, it would confirm what virtually all of our scientific models suggest about life in the universe: that it should be abundant. (In fact, the models suggest that in a given star system life could be very rare, but given the hundreds of billions of star systems in our galaxy, there should still be many containing life.) The discovery of life on a second planet in our own solar system, particularly if it is eventually coupled with evidence that life once existed on the surface of Mars, would be strong evidence that life is even more abundant than most have believed to date. If primitive life is abundant, moreover, it is a strong sign that intelligent life like ourselves is likely to be found in other star systems as well. In fact, if life is found on Europa, it would be a sign that some of our models have actually been too pessimistic. Most scientists believe life is unlikely to emerge outside of a so-called habitability zone, or “Goldilocks” zone, in which a star’s heat and light can create conditions more or less similar to those here on Earth. If life is found on Europa, it would be evidence that life does not need to be in the Goldilocks zone after all.
This is not a violation of basic biological or astronomical theory. Given our best guesses about how life emerges (expressed in the Drake equation) and the assumption that we are more likely to be average than unique (the principle of mediocrity), it logically follows that there should be numerous other places in the galaxy where life exists, and that at least a few of these life forms should have evolved advanced intelligence. To date, however, we have found no solid evidence to support such assumptions – and the Fermi Paradox notes that, if intelligent life was abundant, we should have found such evidence. If life is found on Europa we would know for certain that life away from Earth does in fact exist.
There would probably be much wider-ranging social consequences if life is found on Europa as well. Even setting aside many religious beliefs (which state this explicitly), we tend to think and act on the assumption that life on Earth is unique, and that we are unique among those Earth life forms. Life on Europa would be a signal that life is perhaps not so unique as we believe. We might have to re-think our entire vision of our place in the universe, on a profound level. This need not be seen as an attempt to cheapen human life or make it less special: we would still have no evidence that other alien life forms had made our own progress towards advanced intelligence, and in any case it would not make life any less precious. However, if life is found on Europa, we would need to start thinking of ourselves as inhabitants of a universe of life, rather than simply a planet of life.
All of this, it should be emphasized is still theoretical. Even the existence of an ocean on Europa in the first place is still theoretical, although astronomers are pretty certain on that point. Many were certain we would eventually find life on Mars, too, but that planet seems to be mostly or entirely barren now, even if it was not always that way. It could still be that our future submarine probe will make it to Europa and encounter no life at all.