This Is What Alien Life in Our Solar System Might Look Like

Researchers have found the missing ingredient for life on Saturn's icy ocean moon, Enceladus. But what might this life actually look like?

Enceladus was already believed to be a fairly good candidate for extraterrestrial life. Its vast oceans are known to contain the right salinity and pH to support life. Evidence of hydrothermal vents—structures that shoot out heat energy and nutrients and are believed by many to have been the site of the origin of life on Earth—had been found under its icy surface. And complex carbon-based molecules—the building blocks of life on Earth—and five of the six essential elements for life had been identified there.

But something was still missing: phosphorus.

'Last piece of evidence'

"Phosphorus is seen as one of the six elements essential for life," Frank Postberg, Head of Planetary Sciences and Remote Sensing at the Freie Universität Berlin, told Newsweek. "It is critical for DNA and it is also found in ATP, the energy currency of all our cells."

By studying data from NASA's Cassini mission spacecraft, Postberg and his team were able to detect signs of phosphorus, or more specifically phosphates, on the icy ocean world.

"That was seen as the last piece of evidence for what is needed [for extraterrestrial life]," Postberg said. "And now we have found it! And that's why everyone is pretty excited about it."

The team published their research in the journal Nature, in a paper on June 14.

Phosphorus itself has been found on extraterrestrial material before. But this discovery is different.

"The kicker here is that it's dissolved in the ocean," Postberg said. "It's the first time that phosphates have been detected in any water outside of Earth. You find phosphates in meteoric rocks, for example, but life as we know it needs water to access it—it cannot access it in rocky minerals."

We still do not know for sure whether alien life actually exists on Enceladus, but this discovery makes the icy moon a prime candidate.

"We have found probably the most habitable place outside of Earth on Enceladus, but we still have no clue if life has actually used this opportunity and evolved there," he said.

What would aliens look like?

With the discovery of phosphorus on Enceladus, the obvious question to ask is what potential alien life forms would actually look like?

An answer may come in a paper from researchers at the University of Oxford, published in the International Journal of Astrobiology in 2017. The paper, titled "Darwin's aliens," outlines how the same models of evolution that are used to explain life on Earth could be used to speculate about life on other planets.

"What we were arguing was that we can actually use evolutionary theory to make all these predictions about life on other planets before we even find it," Sam Levin, CEO of biotech start-up MelonFrost and former researcher at the University of Oxford, told Newsweek.

"The texture, the color and the types of sensing organs might be more wild than the imaginations of our best sci-fi movie set designers, but there are aspects in the organism's design and function that will be super familiar," he said.

Life on Enceladus, and indeed any other moon or planet, may have evolved a totally different biochemistry to what we see on Earth. It may not even be made up of DNA. And yet, Levin said that evolutionary biology holds true independent of the building block beneath it.

"Darwin, for example, formed his theory of evolution without knowing anything about DNA or the biochemistry of life," he said. "There is only one way to get complex life and that is through evolution by natural selection."

Because of this, we can theorize that organisms on other planets will be held to the same set of evolutionary rules as we are on Earth.

"These entities will be designed to maximize their fitness," Levin said. "However wacky the blip bloops on Enceladus are, they will be trying to have more babies."

These rules apply to all organisms, even the simplest of bacteria. But to evolve complex life, other factors must also be considered.

"Cooperation is huge for the evolution of life on Earth for anything above a single cell," Stuart West, a zoology professor at the University of Oxford and co-author on the "Darwin's aliens" paper, told Newsweek. "So, if we were to find anything that could be seen with the naked eye, it's going to involve cooperation at some level, which might be bringing things together into a higher-level organism."

To understand how this works in practice, Levin compared the human body to a Russian matryoshka nesting doll: Each of us is made up of a collection of different organs that work together to help us eat and navigate the world; each organ is made up of a bunch of cells collaborating to help the organ carry out its specific function; each of those cells is instructed by genes, collaborating and cooperating with other genes and so on.

"At each level, the entities above are trying to maximize the fitness of the entities below," Levin said. "One of the most exciting predictions we can make about [potentially complex] life on Enceladus is that there will also be a similar kind of nested hierarchy of entities which will be clustered together into this larger structure where all the parts are cooperating together to help the organism make more copies."

Using these rules of cooperation and self-replication, Levin and West, along with their co-authors Thomas Scott and Helen Cooper, were able to make predictions about what an extra-terrestrial organism might actually look like.

The creature described in their paper, which they called "The Octomite," resembles a sort of budding tardigrade, or micro-animal, on steroids. It is comprised of a hierarchy of entities with aligned evolutionary interests where each part is able to specialize on a specific task. The creature can also reproduce itself by budding off smaller, larvae-like creatures that then swim or fly off to start a new life elsewhere.

Of course, the features of any life form on Enceladus will have evolved under a very different set of environmental circumstances than we have here on Earth.

"It might be totally dark," Levin said. "That has the potential to be one of the most exciting things about the potentially complex life forms there—if we could find an entire ecology that has evolved for billions of years in the darkness. We certainly wouldn't expect to find eyes, but other sensing organs might become much more exaggerated.

"You could maybe look at life found in the deep sea or caves to see something equivalent, but these [aliens] would have had a much longer period in the dark."

On Earth, we often see features, like eyes, evolving independently numerous times.

"We see the convergent evolution of features time and time again," West said. "Compare the Australian marsupial mammals with the placental mammals—in both cases you get something that's good at digging into the ground. But a placental mole is actually closer genetically to a blue whale than it is to a marsupial mole."

However, Levin said that it was difficult to make predictions about such features developing on other worlds.

"Obviously that is context or environment dependant," he said. "[Eyes have evolved several times] on Earth because light is an abundant source of information. We also don't know if DNA lends itself to the repeated emergence of certain kinds of traits."

Such algorithmic principles apply beyond making predictions about life on other planets. Levin uses these same evolutionary rules to "evolve aliens on Earth" with his start-up company MelonFrost.

"We've built a technology for rapidly evolving mircrobes for various applications," he said. "We built this crazy machine, which we call the evolution reactor, where we basically grow thousands of independent populations of microbes and run these evolution experiments in parallel."

This technology can be used to generate microbes that are able to produce a range of what would today be synthetic commodities, like cleaning solutions, textile fibers and food.

"In the same way that we can make predictions about life on some distant moon, we can rely on the algorithmic nature of evolution to harness biology here on Earth to make new sustainable materials," Levin said.

But what next for Enceladus?

"We will continue to analyse the data from Cassini," Postberg said. "But, at the same time, we are already ramping up preparation for the next big ocean world missions. Europa Clipper will launch in about a year to visit the ocean moons of Jupiter, not Saturn, and then we can really compare where is the best place to look for actual life."