One of the most profound questions we face is that of if we are alone in the universe. In 1950, influential and notable physicist Enrico Fermi was working for Los Alamos National Laboratory, and suggested almost half jokingly that if there were space-faring civilizations were out there in the cosmos we should have probably heard from them by now. He famously asked “Where is everybody?” and we still don’t really have an answer to that. Fermi was puzzled by the fact that, if such civilizations existed, they hadn’t visited or found us yet. In his opinion, if they were out there, they would have exponentially broken their barriers and moved out into the galaxy, colonizing new worlds, and we would have surely known about them by now, and it is a good question. Where are they? There are a lot of proposed reasons for why we haven’t found anyone, which I have covered before, but recently there has been talk of yet another reason. Perhaps the answer to the question of where all of the aliens are is that they are all buried under miles of ice, far from our prying eyes and efforts to find them.
Perhaps one of the problems with finding life in the universe besides our own is that we are simply not looking in the right places. There has been much effort directed by scientists at looking for “Earth-like planets,” that is, planets that are much like our own and which we deem to be the most habitable and welcoming to us. These are the planets that sit just the right distance from their star, called the “Goldilocks Zone,” to have a habitable temperature, an atmosphere conducive to life, with plentiful oxygen and organic molecules, and most important of all liquid water. These are the basic ingredients we have proclaimed to be crucial for life as we know it, and it makes sense that we should deem planets similar to our own to be the best candidates for life and try to find them. After all, the only life we truly know of in the universe, that of our own world, developed in these conditions. But what if alien life is somewhere else, not on the surface, but beneath it?
While all of this effort is being made to find second Earths, and several have been indeed located, a far more common type of planet is thought to be frozen worlds and moons encased in rock and ice, but harboring vast liquid oceans below. In fact, it is widely believed that such watery worlds are perhaps 1,000 times more common than rocky, earth-type planets. To give an idea of just how common this type of world is, we need only look to our own solar system, which holds many examples. For instance, Jupiter’s moons Callisto, Ganymede, and Europa are all thought to have liquid oceans buried by miles of ice and rock, as are Saturn’s moons Titan, Dione, and Enceladus, Neptune’s moon Triton, and others, all with these oceans kept in their liquid state through geothermal activity and the affects of tides and gravitational forces. Not only do such worlds have liquid water in plentiful supply, but through geothermal activity they hold the chance of having habitable conditions and the necessary nutrients and ingredients for life even outside of the magic Goldilocks Zone. Indeed, even planets within our own star’s Goldilocks Zone aren’t really habitable, such as Mars and Venus, so maybe this is a key, and looking at these subsurface oceans potentially opens up the doors to further planets we can search for life on.
In addition, these types of habitats hold other advantages as well, because since they are located so far under, hazardous surface conditions wouldn’t necessarily affect them. One NASA physicist Alan Stern has said of this, “Impacts and solar flares, and nearby supernovae, and what orbit you’re in, and whether you have a magnetosphere, and whether there’s a poisonous atmosphere — none of those things matter.” Another group of scientists who think so are Manasvi Lingam and Abraham Loeb, of the Harvard Smithsonian Center for Astrophysics and the Institute for Theory and Computation at Harvard University, who have written a whole study on this called Subsurface Exolife. Lingham has said of the benefits of a subsurface existence in these alien oceans:
The conventional notion of planetary habitability is the habitable zone (HZ), namely the concept that the “planet” must be situated at the right distance from the star such that it may be capable of having liquid water on its surface. However, this definition assumes that life is: (a) surface-based, (b) on a planet orbiting a star, and (c) based on liquid water (as the solvent) and carbon compounds. In contrast, our work relaxes assumptions (a) and (b), although we still retain (c). One major advantage that icy worlds have is that the subsurface oceans are mostly sealed off from the surface. Hence, UV radiation and cosmic rays (energetic particles), which are typically detrimental to surface-based life in high doses, are unlikely to affect putative life in these subsurface oceans.
We have seen whole sophisticated ecosystems around hydrothermal vents on Earth in areas previously thought to be hostile for life, so it is a promising idea. Yet, there are still some drawbacks to the notion, as Lingham has said:
On the negative side, the absence of sunlight as a plentiful energy source could lead to a biosphere that has far less organisms (per unit volume) than Earth. In addition, most organisms in these biospheres are likely to be microbial, and the probability of complex life evolving may be low compared to Earth. Another issue is the potential availability of nutrients (e.g. phosphorus) necessary for life; we suggest that these nutrients might be available only in lower concentrations than Earth on these worlds.
Nevertheless, such icy worlds are coming to be seen as more and more promising as a potential candidate for alien life, and such biospheres are even thought to very plausibly be able to spawn highly intelligent life. Yet, if these vast oceans did produce intelligent life comparable to or beyond human intelligence, the main problem would be even knowing they are there at all. Some of these worlds have miles and miles of rock or ice between the surface and the water, meaning that communication with radio signals might not be an option. Stern has explained, “If they have technology, and let’s say they’re broadcasting, or they have city lights or whatever — we can’t see it in any part of the spectrum, except maybe very-low-frequency.” There would also be a lack of biosignatures on the surface to give a clue as to any life that might lie below, as the surface could be completely forbidding and barren. It seems that really the only way to know if they exist is if they contacted us or if we physically went and drilled down to them. Professor Loeb has said of these challenges:
It is very difficult to detect sub-surface life remotely (from a large distance) using telescopes. One could search for excess heat but that can result from natural sources, such as volcanos. The most reliable way to find sub-surface life is to land on such a planet or moon and drill through the surface ice sheet. This is the approach contemplated for a future NASA mission to Europa in the solar system.
Adding to this is that even if there are highly intelligent civilizations under the ice, living in such an environment would not be conducive to space travel, as they would have to bore through all of that surface, and water would be a very heavy and difficult medium to transport into orbit and over very long distances. It has even been suggested by scientists like Stern that they might not even be aware that there is space out there over their heads at all, with the universe perhaps all effectively ending for them with the impenetrable wall above them. There has also been speculation that intelligent life would need a mastery of fire to really develop machines and technology, which would be impossible in their watery realm. For instance, dolphins and octopuses have in recent years been speculated as being possibly of human-level intelligence, but their biome makes development of any sophisticated technology a challenge. Could that be happening here? There is no way to know.
What we do know is that these icy planets and moons do exist, along with ample water and quite probably the elements necessary for life. We also know that they are likely far more common than rocky, earth-like worlds. Is it at least possible that if there has evolved intelligent life outside of our own it had done so in one of these environments? If so, what does that mean for our efforts to search out and contact such life? Due to their extreme circumstances is it likely we will ever detect them or meet them? Whatever the case may be, it poses an interesting possibility for the Fermi Paradox, and at the very least truly expands the locales we should be looking at for life in the universe besides our own.