The life which swarms around deep sea vents on Earth may be a clue as to what life may look like at the bottom of alien seas. Credit: Getty Images.
Life on Earth depends on cell membranes made of phospholipids: molecular chains with phosphorus-oxygen heads and carbon-chain tails that bind to each other to form a flexible membrane in water. As far as multicellular aliens are concerned, she says, things may get more complicated. If life does exist in the oceans of moons such as Europa, it will likely be microbial and have to rely on chemosynthesis to provide energy.
Nasa announced this summer that its Dragonfly mission will launch in and arrive on Titan in It will land a drone-like craft to explore dozens of promising locations and look for signs of life.
Recent discoveries have led astrobiologists to think that moons are the most promising places for alien life to exist in our Solar System. Questions about life's origins and its future are complicated, and must be certain we become that our planet isn't the only one suitable for life.
This would be the first opportunity to explore a sea on another world, and it could inform the design of future submarines to explore the subsurface waters of Europa and other moons. The mission is still in its conceptual stage, some 20 years away, with scientists and engineers starting to investigate how to even build such a submarine. Intriguingly, Titan is also thought to have a liquid ocean of water deep beneath its icy outer layer, which would mean that in addition to its exotic surface life based on liquid methane, there could exist more Earth-like life under its surface.
Some scientists think this moon has several different layers of ocean, separated by different types of ice that form at different depths and pressures. If this is the case, each layer could, in theory, host different lifeforms adapted to local conditions at that depth.
Nasa is also discussing sending a lander to Europa , as early as Saturn's moons may be freezing cold, but there is still liquid water under the thick expanses of ice Credit: Getty Images. And, there is a private, Nasa-backed plan for a mission to Enceladus to look for life there that could take off in if it gets the green light later this year. But to really figure out what life might exist in these alien oceans, we will need to send a submersible, which will be tricky as such a vehicle would have to drill through several kilometres of ice to even reach the ocean.
Nasa is funding some conceptual studies on how to do that. Their bot would sample ice and water as it descended, sending information back to the surface through a fibre optic cable. But, if lifeforms there turn out to be truly alien, we might struggle to detect them.
In the distant future, though, some five billion years from now, when our Sun runs out of hydrogen fuel and starts expanding into a red giant phase before it eventually dies, it will melt the ice on these moons and turn them into much more Earth-like places. There should be liquid water on their surface and more temperate climates, perhaps opening up the possibility of life evolving there then — or at least harbouring refugees from the scorched Earth.
In the distant future, if we are to survive, we will all have to become migrants and hope these newly habitable worlds welcome us as our own world gets too hot for life. Did you enjoy this story? Then we have a favour to ask.
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The space submarine hunting for aliens The religious implications of first contact There is now evidence for water oceans on several moons, including Europa, Enceladus, Callisto and Ganymede. This is much more advanced than what most scientists expect to find there. Methane-based life would need an alternative way to form cells. Some suggest aliens might be hibernating , or that something mysterious is preventing their evolution from taking place. Or maybe they just don't want anything to do with us? Last year, theoretical physicist Alexander Berezin from the National Research University of Electronic Technology MIET in Russia put forward his own explanation for why we're seemingly alone in the Universe, proposing what he calls his "First in, last out" solution to the Fermi Paradox.
According to Berezin's pre-print paper , which hasn't as yet been reviewed by other scientists, the paradox has a "trivial solution, requiring no controversial assumptions" but may prove "hard to accept, as it predicts a future for our own civilisation that is even worse than extinction". As Berezin sees it, the problem with some proposed solutions to the Fermi Paradox is they define alien life too narrowly.
Of course, even with such a wide scope, we're still not seeing evidence of these things out there in the cosmos. But for the purposes of solving the paradox, Berezin says the only parameter we should concern ourselves with — in terms of defining extraterrestrial life — is the physical threshold at which we can observe its existence.
If an alien civilisation doesn't somehow reach parameter A — whether by developing interstellar travel , broadcasting communications across space , or by other means — it might still exist, but not help us solve the paradox. As Berezin explains, this doesn't necessarily mean a highly developed extra-terrestrial civilisation would consciously wipe out other lifeforms — but perhaps "they simply won't notice, the same way a construction crew demolishes an anthill to build real estate because they lack incentive to protect it".
So is Berezin suggesting that we are the ants, and the reason we haven't encountered aliens is because we simply haven't had our own civilisation unthinkingly demolished by such unimaginably superior life forms yet? Because we are probably not the ants, but the future destroyers of the very worlds we've been looking for this whole time.