5 Incredible Places to Look for Alien Life

When pondering the prospects of alien life in the universe, the mind quickly jumps to the highly-advanced civilizations of sci-fi, creatures with big grey heads and dark eyes, able to traverse the cosmos in ways humanity can only dream of. Unfortunately, the chances of such a species existing and visiting us seem to be little more than a fantasy, and while it would be pretty cool to receive highly advanced technology beyond our wildest imagination, reality is a lot more mundane. In the search for extraterrestrial life, the likes of NASA and the European Space Agency are far more interested in looking for microorganisms, specs of life that may have independently evolved from that on earth and are perhaps still around today.

And we don’t need interstellar travel to look for signs of such life, as our very own solar system is ripe with several places that could potentially harbor alien life. Today we’re going to cover five of these places, ranked in order of how likely we think they are to be the place we finally discover life outside of our own planet.

5. Ceres

In fifth place we have Ceres. Named after the Roman goddess of the harvest, it’s the largest object in the asteroid belt. In fact, Ceres is so large that it’s actually classified as a dwarf planet, and contains about 25% of all the mass present in the entire asteroid belt. It’s often referred to as an embryonic planet, because it seems to have begun the process of planet formation but got interrupted at some point, probably by the immense mass of nearby Jupiter.

Ceres has an incredibly thin atmosphere, its surface is rocky and cold with large salt deposits, and the temperature can drop to a chilly -225 degrees Fahrenheit, or -143 Celsius. If your instincts are telling you that this isn’t a great place to look for life, you’re probably right, its surface seems to be outright inhospitable.

But the reason Ceres makes this list is the fairly recent discovery of what lies beneath this frozen hellscape. In 2015, NASA’s space probe Dawn entered orbit around Ceres, where it would hang out for the next three years. During its time there, the probe came incredibly close to the surface, and gathered crucial data that scientists worked around the clock to interpret. What they found was that there’s a high likelihood that Ceres contains a subsurface ocean.

And not only that, but the ocean almost certainly consists of salt water.

The salinity is the crucial finding here, because it means that even on a frozen world like Ceres, salt lowers water’s freezing temperature, allowing it to stay in liquid form, and thus providing a potential habitat for subsurface life.

And because many of the salt deposits on the surface are relatively young, having formed within the last million years or so, it’s likely that whatever process brought them to the surface is still active, which could mean some form of thermal activity.

It’s also important to note that if this ocean does exist, it is really, really big. Current estimates place the total amount of water at nearly 25% of Ceres’ mass, meaning that it would actually have more water than all of earth’s oceans combined. All of this points to the possibility that microscopic life could flourish in this watery mantle, or, that it may have at some point in the past.

But it doesn’t seem like we’ll know for quite some time. There are no currently planned missions to land on Ceres in the near future, and even if there were, it would be quite the technological feat to drill through the surface. So don’t expect life on Ceres to be confirmed or denied anytime soon, just know that it’s certainly a great candidate for potential life in the solar system.

4. Mars

In fourth place we have Mars, the fourth planet from the sun and arguably the one we know the most about aside from earth. It’s long been the subject of speculation for alien life, going as far back as the 19th century, when astronomers believed the surface was covered in straight canals, supposedly constructed by extraterrestrials, along with large oceans. This was all debunked a few years later, but the idea that Mars may be home to life is a sentiment that has yet to leave. To date, there have been six different rovers landed on the red planet, 5 from NASA and one from the China National Space Administration, all of which have gathered and analyzed soil and rock samples, atmospheric conditions, and more.

Two of the rovers, Opportunity and Curiosity, were reported to be searching for signs of extraterrestrial life, specifically looking for organic compounds, microscopic fossils, and traces of ancient water. What we’ve learned from all this exploration, and the many probes that have circled and photographed the planet, is that Mars was once a very different place from the barren, red landscape we see today. Long ago, the planet was home to plenty of liquid water, which altered the landscape in ways we can still detect today.

The only remains of this water are found in the frozen ice caps, as the atmospheric conditions no longer allow liquid water to remain on the surface, but the idea that it was once there raises some tantalizing questions. Was Mars once earthlike? Was it home to a variety of organisms that went extinct billions of years ago?

If life did exist, even microscopic life, we may be able to find its fossils if any remain on the surface, or other traces of life that once was. In fact, according to some scientists, we may have already come across such traces. In 1984 a meteorite was picked up in Antarctica, and it was found to be of Martian origin. Specifically, it broke off from Mars around 4 billion years ago, during the time when the planet was home to water.

To avoid earthly contamination, samples were taken from the interior of the meteorite, where the team found small, orange, carbonate globules, or droplets.

After analyzing these droplets, the team found three pieces of evidence to suggest the presence of ancient microscopic life. First, they found polycyclic aromatic hydrocarbons, or PAH, a type of complex organic compound. Second, trace amounts of magnetite and iron sulfide, which apparently are rarely found together in the presence of carbonates unless influenced by bacterial processes. And third, when examined under a microscope, the rock contained numerous worm-like tubes that resembled fossilized bacteria.

The team admits that any one of these findings could be explained in a way that doesn’t invoke extraterrestrial life, but they argue that the presence of all three is too coincidental to ignore. Obviously this proposal was met with a lot of controversy, and is by no means definitive proof, but it is possible evidence that there’s much more to the red planet than meets the eye.

It’s highly unlikely that anything remains living on the surface of Mars, the conditions are simply too brutal, but there is recent evidence of small lakes beneath its surface, just a couple kilometers down. We’ve found bacteria on earth living in similar conditions, so who’s to say they wouldn’t be able to do the same in our neighboring world.

So stay tuned, because as American and Chinese rovers continue to scour Mars, there are certainly more than a few surprises waiting for us, and one of them may be evidence of alien life.

3. Titan

In third place we have Titan, one of the most complex and interesting worlds in the solar system. Titan is Saturn’s largest moon, and boasts a fully developed atmosphere of nitrogen, methane, and hydrogen. Titan is also the only place in the solar system aside from earth that is known to have liquid lakes, rivers, and seas on its surface.

Only these lakes and rivers aren’t made of water, they’re actually composed of methane and ethane, as the surface of Titan is so cold that water only exists as ice. However, beneath its icy shell, it is speculated to be home to a layer of liquid water.

It is also geologically active, keeping the interior warm. Overall it ranks very high in habitability, just not for organisms like humans or fish. It’s hypothesized that if life exists on Titan, it could be very different from the water-based organisms we are accustomed to on earth, and may instead consume hydrogen, react the hydrogen with acetylene, and produce methane as a result. Organisms that produce methane are known as methanogens, and they do exist on earth, only on our planet they react hydrogen with carbon dioxide.

If these proposed methanogens are present on the surface of Titan, there are a few ways we could detect traces of them. The easiest of these would be to measure the levels of hydrogen and acetylene, which would be lower than expected due to their consumption. Interestingly, evidence consistent with this was reported in 2010, when researchers from John Hopkin’s University found that hydrogen levels drop off sharply near the surface as opposed to the high atmosphere, and that the surface has very low levels of acetylene.

There are alternative explanations for these findings, though, such as a currently unknown mineral process that allows hydrogen and acetylene to react chemically, without the need for life. Researchers have noted that finding such a new process would be extraordinary, though obviously less extraordinary than alien life.

Whether or not any of this is plausible should be answered in the coming years, as the NASA mission Dragonfly is planned to launch in 2027 and arrive on Titan in 2034. Dragonfly will not simply be a rover like we’ve seen before, but actually a rotorcraft with the ability to vertically take off and land in suitable places on the surface, giving it the ability to sample many different locations across Titan.

However, one astrobiologist has pointed out that even if we do find life on Titan, it may still be of earthly origin. Just as scientists speculated that microscopic fossils were blasted off the surface of mars and ended up on earth, so too may chunks of microbe-rich rocks have been knocked off the surface of our planet long ago, potentially landing on Titan and managing to survive and adapt. It would still be an incredible find, but may not necessarily mean that other life independently originated outside earth.

Regardless, the complex chemistry of Titan makes it a compelling place to potentially house life, and hopefully Dragonfly can shed some more light on this by the mid-2030s.

2. Venus

In second place we have Venus, the second planet from the sun and one that is remarkably similar to earth in terms of size and mass. Venus has an incredibly thick atmosphere, which obscures the planet’s surface and left it the subject of speculation for many years. Some believed that beneath the clouds were rather earthlike conditions, maybe a massive desert, or perhaps a world made entirely of water, with no land at all.

One popular theory was that the surface was covered in thick jungles, a result of immense rainfall from the thick cloud cover. Such a climate was envisioned by authors HP Lovecraft, Ray Bradbury, and many more.

Unfortunately, none of this is even close to true, and we’ve since learned that the surface of Venus is rocky and blazing hot. There is extensive volcanism, and the average surface temperature is around 850 degrees Fahrenheit, or about 450 degrees Celsius, which, by the way, is hot enough to melt lead. The atmosphere is made of 95% carbon dioxide, and the pressure it exerts on the surface is simply crushing, nearly 100 times that found on earth.

Suffice to say, no life as we know it would survive for very long on the Venusian surface, and hopes that it contained extraterrestrial life largely died out following these revelations in the 60s and 70s.

However, soon after, the focus shifted away from the absolute hell of a surface, and toward the upper layers of the atmosphere, where conditions are surprisingly pleasant. For decades, scientists have speculated that extremophile microorganisms may live in the upper, cooler layers of the atmosphere, where water and sunlight can be found, allowing for potential photosynthesis. This was originally suggested by astronomer Carl Sagan, but more recently in 2019 when researchers reported peculiar bands of UV absorbance in the atmosphere, caused by what they dubbed an ‘unknown absorber’. They stated that this unknown absorber may be a chemical reaction that we’ll understand one day with more information about the atmospheric conditions, or it may be the result of large colonies of microbial life taking energy from the sun’s rays.

Further speculation suggests that volcanic activity could blast vital nutrients up into the atmosphere, sustaining whatever life may be thriving amongst the dense clouds.

But the real reason Venus is such a hot topic right now is because of the 2020 report that phosphine had been detected in the atmosphere. Phosphine is a gas, and while it can form inorganically, the conditions required to create a substantial amount of it are not present in Venus’s atmosphere, or on any rocky planet for that matter, leading the researchers to conclude that it may be of organic origin, and thus a biosignature for life above Venus. Since then, several more analyses have spotted said phosphine in the atmosphere, albeit generally a bit less than in the original report, but still in significant quantities.

In wake of these findings, NASA administrator Jim Bridenstine publicly called on researchers to dig deeper into the data, referring to the discovery of phosphine as “the most significant development yet in building the case for life off Earth”.

Confirmation of these findings may come within the next decade, as NASA is currently planning an exploratory mission to Venus, the VERITAS spacecraft, with 2029 as the earliest expected launch date. However, budget shortfalls have taken a hit on the project, and there’s a chance it may get canceled altogether.

1. Europa

Coming in at first place, arguably the best place to search for life in the solar system, we have Europa, one of Jupiter’s 95 known moons and the sixth largest in the solar system.

Europa’s surface is a smooth sheet of ice, and the current scientific consensus is that beneath this ice lies a vast subsurface ocean of liquid water. And not just any subsurface ocean, because Europa’s tidal forces are thought to create an internal circulation, creating currents that keep the water constantly moving. This interaction and constant motion have led astronomers to hypothesize that the water below may be in a constant cycle that eventually brings it to the surface, meaning that when we eventually land on Europa, we may not need to dig through the ice to look for signs of life, as it may be waiting on the icy surface.

It’s also been hypothesized that radiation striking the ice could create oxygen that makes its way down into the ocean, and scientists have spotted clay-like deposits that supposedly contain organic compounds, meaning Europa as a whole has conditions seemingly more than suitable for life.

As promising as it sounds, other scientists are more skeptical. Some have proposed that the subsurface ocean almost never interacts with the surface, and that the ice sheet is far thicker than previously thought, perhaps containing a thick layer of slightly warmer ice and only containing liquid water more than a hundred miles down. If this is true, we would have a very difficult time reaching potential life on the icy moon.

More information on Europa and its potential habitability is expected in the coming years, as the European Space Agency recently launched the Jupiter Icy Moon Explorer, or JUICE probe. JUICE plans to orbit and study three of Jupiter’s moons, Ganymede, Callisto, and Europa. This mission will likely overlap with a planned NASA mission, the Europa Clipper, which is set to launch in October 2024.

With all these launches searching for life in the solar system, the future holds some interesting developments, and perhaps in 10 years this video will look hilariously outdated.

Key Takeaways

• NASA and ESA focus on finding microorganisms, not advanced civilizations, in the solar system.
• Ceres, Mars, Titan, Venus, and Europa are top candidates for potential extraterrestrial life.
• Ceres may harbor a subsurface saltwater ocean, potentially supporting microscopic life.
• Mars shows signs of past liquid water and possible ancient microbial life.
• Europa is considered the best place to search for life due to its subsurface ocean.

Sources

• Original Side Projects video: 5 Incredible Places to Look for Alien Life

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