There may be no bigger question than whether we are alone in our solar system. As our spacecraft find new clues about the presence of liquid water now or in the past on Mars, the possibility of some kind of life there looks more likely. On Earth, water means life, and that’s why the exploration of Mars is guided by the idea of following the water.
But the search for life on Mars is paired with plenty of strong warnings about how we must sterilize our spacecraft to avoid contaminating our neighbor planet. How will we know what’s native Martian if we unintentionally seed the place with Earth organisms? A popular analogy points out that Europeans unknowingly brought smallpox to the New World, and they took home syphilis. Similarly, it is argued, our robotic explorations could contaminate Mars with terrestrial microorganisms.
Space agencies have long prioritized preventing contamination over our hunt for life on Mars. Now is the time to reassess and update this strategy – before human beings get there and inevitably introduce Earth organisms despite our best efforts.
What Planetary Protection Protocols Do
Arguments calling for extra caution have permeated Mars exploration strategies and led to the creation of specific guiding policies, known as planetary protection protocols.
Strict cleaning procedures are required on our spacecraft before they’re allowed to sample regions on Mars which could be a habitat for microorganisms, either native to Mars or brought there from Earth. These areas are labeled by the planetary protection offices as “Special Regions.”
The worry is that, otherwise, terrestrial invaders could jeopardize potential Mars life. They also could confound future researchers trying to distinguish between any indigenous Martian life forms and life that arrived as contamination from Earth via today’s spacecraft.
The sad consequence of these policies is that the multi-billion-dollar Mars spacecraft programs run by spaceagencies in the West have not proactively looked for life on the planet since the late 1970s.
That’s when NASA’s Viking landers made the only attempt ever to find life on Mars (or on any planet outside Earth, for that matter). They carried out specific biological experiments looking for evidence of microbial life. Since then, that incipient biological exploration has shifted to less ambitious geological surveys that try to demonstrate only that Mars was “habitable” in the past, meaning it had conditions that could likely support life.
Even worse, if a dedicated life-seeking spacecraft ever does get to Mars, planetary protection policies will allow it to search for life everywhere on the Martian surface, except in the very places we suspect life may exist: the Special Regions. The concern is that exploration could contaminate them with terrestrial microorganisms.
Can Earth Life Make It On Mars?
Consider again the Europeans who first journeyed to the New World and back. Yes, smallpox and syphilis traveled with them, between human populations, living inside warm bodies in temperate latitudes. But that situation is irrelevant to Mars exploration. Any analogy addressing possible biological exchange between Earth and Mars must consider the absolute contrast in the planets’ environments.
A more accurate analogy would be bringing 12 Asian tropical parrots to the Venezuelan rainforest. In 10 years we may very likely have an invasion of Asian parrots in South America. But if we bring the same 12 Asian parrots to Antarctica, in 10 hours we’ll have 12 dead parrots.
We’d assume that any indigenous life on Mars should be much better adapted to Martian stresses than Earth life is, and therefore would outcompete any possible terrestrial newcomers. Microorganisms on Earth have evolved to thrive in challenging environments like salt crusts in the Atacama desert or hydrothermal vents on the deep ocean floor. In the same way, we can imagine any potential Martian biosphere would have experienced enormous evolutionary pressure during billions of years to become expert in inhabiting Mars’ today environments. The microorganisms hitchhiking on our spacecraft wouldn’t stand much of a chance against super-specialized Martians in their own territory.
So if Earth life cannot survive and, most importantly, reproduce on Mars, concerns going forward about our spacecraft contaminating Mars with terrestrial organisms are unwarranted. This would be the parrots-in-Antarctica scenario.
On the other hand, perhaps Earth microorganisms can, in fact, survive and create active microbial ecosystems on present-day Mars – the parrots-in-South America scenario. We can then presume that terrestrial microorganisms are already there, carried by any one of the dozens of spacecraft sent from Earth in the last decades, or by the natural exchange of rocks pulled out from one planet by a meteoritic impact and transported to the other.
In this case, protection protocols are overly cautious since contamination is already a fact.
Technological Reasons the Protocols Don’t Make Sense
Another argument to soften planetary protection protocols hinges on the fact that current sterilization methods don’t actually “sterilize” our spacecraft, a feat engineers still don’t know how to accomplish definitively.
The cleaning procedures we use on our robots rely on pretty much the same stresses prevailing on the Martian surface: oxidizing chemicals and radiation. They end up killing only those microorganisms with no chance of surviving on Mars anyway. So current cleaning protocols are essentially conducting an artificial selection experiment, with the result that we carry to Mars only the most hardy microorganisms. This should put into question the whole cleaning procedure.
Further, technology has advanced enough that distinguishing between Earthlings and Martians is no longer a problem. If Martian life is biochemically similar to Earth life, we could sequence genomes of any organisms located. If they don’t match anything we know is on Earth, we can surmise it’s native to Mars. Then we could add Mars’ creatures to the tree of DNA-based life we already know, probably somewhere on its lower branches. And if it is different, we would be able to identify such differences based on its building blocks.
Mars explorers have yet another technique to help differentiate between Earth and Mars life. The microbes we know persist in clean spacecraft assembly rooms provide an excellent control with which to monitor potential contamination. Any microorganism found in a Martian sample identical or highly similar to those present in the clean rooms would very likely indicate contamination – not indigenous life on Mars.
The Window Is Closing
On top of all these reasons, it’s pointless to split hairs about current planetary protection guidelines as applied to today’s unmanned robots since human explorers are on the horizon. People would inevitably bring microbial hitchhikers with them, because we cannot sterilize humans. Contamination risks between robotic and manned missions are simply not comparable.
Whether the microbes that fly with humans will be able to last on Mars is a separate question – though their survival is probably assured if they stay within a spacesuit or a human habitat engineered to preserve life. But no matter what, they’ll definitely be introduced to the Martian environment. Continuing to delay the astrobiological exploration of Mars now because we don’t want to contaminate the planet with microorganisms hiding in our spacecrafts isn’t logical considering astronauts (and their microbial stowaways) may arrive within two or three decades.
Prior to landing humans on Mars or bringing samples back to Earth, it makes sense to determine whether there is indigenous Martian life. What might robots or astronauts encounter there – and import to Earth? More knowledge now will increase the safety of Earth’s biosphere. After all, we still don’t know if returning samples could endanger humanity and the terrestrial biosphere. Perhaps reverse contamination should be our big concern.
The main goal of Mars exploration should be to try to find life on Mars and address the question of whether it is a separate genesis or shares a common ancestor with life on Earth. In the end, if Mars is lifeless, maybe we are alone in the universe; but if there is or was life on Mars, then there’s a zoo out there.
From blob-like jellyfish to rock-like lichens, our planet teems with such diversity of life that it is difficult to recognise some organisms as even being alive. That complexity hints at the challenge of searching for life as we don’t know it – the alien biology that might have taken hold on other planets, where conditions could be unlike anything we’ve seen before. ‘The Universe is a really big place. Chances are, if we can imagine it, it’s probably out there on a planet somewhere,’ said Morgan Cable, an astrochemist at the Jet Propulsion Laboratory in Pasadena, California. ‘The question is, will we be able to find it?’
For decades, astronomers have come at that question by confining their search to organisms broadly similar to the ones here. In 1976, NASA’s Viking landers examined soil samples on Mars, and tried to animate them using the kind of organic nutrients that Earth microbes like, with inconclusive results. Later this year, the European Space Agency’s ExoMars Trace Gas Orbiter will begin scoping out methane in the Martian atmosphere, which could be produced by Earth-like bacterial life. NASA’s Mars 2020 rover will likewise scan for carbon-based compounds from possible past or present Mars organisms.
But the environment on Mars isn’t much like that on Earth, and the exoplanets that astronomers are finding around other stars are stranger still – many of them quite unlike anything in our solar system. For that reason, it’s important to broaden the search for life. We need to open our minds to genuinely alien kinds of biological, chemical, geological and physical processes. ‘Everybody looks for “biosignatures”, but they’re meaningless because we don’t have any other examples of biology,’ said the chemist Lee Cronin at the University of Glasgow.
To open our minds, we need to go back to basics and consider the fundamental conditions that are necessary for life. First, it needs some form of energy, such as from volcanic hot springs or hydrothermal vents. That would seem to rule out any planets or moons lacking a strong source of internal heat. Life also needs protection from space radiation, such as an atmospheric ozone layer. Many newly discovered Earth-size worlds, including ones around TRAPPIST-1 and Proxima Centauri, orbit red dwarf stars whose powerful flares could strip away a planet’s atmosphere. Studies by the James Webb Space Telescope (JWST), set to launch next year, will reveal whether we should rule out these worlds, too.
Finally, everything we know about life indicates that it requires some kind of liquid solvent in which chemical interactions can lead to self-replicating molecules. Water is exceptionally effective in that regard. It facilitates making and breaking chemical bonds, assembling proteins or other structural molecules, and – for an actual organism – feeding and getting rid of waste. That’s why planetary scientists currently focus on the ‘habitable zone’ around stars, the locations where a world could have the right temperature for liquid water on its surface.
These constraints still leave a bewildering range of possibilities. Perhaps other liquids could take the place of water. Or a less exotic possibility: maybe biology could arise in the buried ocean on an ice-covered alien world. Such a setting could offer energy, protection and liquid water, yet provide almost no outward sign of life, making it tough to detect. For planets around other stars, we simply do not know enough yet to say what is (or is not) happening there. ‘It’s difficult to imagine that we could definitively find life on an exoplanet,’ conceded Jonathan Lunine, a planetary scientist at Cornell University. ‘But the outer solar system is accessible to us.’
The search for exotic life therefore must begin close to home. The moons of Saturn and Jupiter offer a test case of whether biology could exist without an atmosphere. Jupiter’s Europa and Saturn’s Enceladus both have inner oceans and internal heat sources. Enceladus spews huge geysers of water vapour from its south pole; Europa appears to puff off occasional plumes as well. Future space missions could fly through the plumes and study them for possible biochemicals. NASA’s proposed Europa lander, which could launch in about a decade, could seek out possible microbe-laced ocean water that seeped up or snowed back down onto the surface.
Meanwhile, another Saturn moon, Titan, could tell us whether life can arise without liquid water. Titan is dotted with lakes of methane and ethane, filled by a seasonal hydrocarbon rain. Lunine and his colleagues have speculated that life could arise in this frigid setting. Several well-formulated (but as-yet unfunded) concepts exist for a lander that could investigate Titan’s methane lakes, looking for microbial life.
For the motley bunch of exoplanets that have no analog in our solar system, however, scientists have to rely on laboratory experiments and sheer imagination. ‘We’re still looking for the basic physical and chemical requirements that we think life needs, but we’re trying to keep the net as broad as possible,’ Cable said. Exoplanet researchers such as Sara Seager at the Massachusetts Institute of Technology and Victoria Meadows at the University of Washington are modelling disparate types of possible planetary atmospheres and the kinds of chemical signatures that life might imprint onto them.
Now the onus is on NASA and other space agencies to design instruments capable of detecting as many signs of life as possible. Most current telescopes access only a limited range of wavelengths. ‘If you think of the spectrum like a set of venetian blinds, there are only a few slats removed. That’s not a very good way to get at the composition,’ Lunine said. In response, astronomers led by Seager and Scott Gaudi of the Ohio State University have proposed the Habitable Exoplanet Imaging Mission (HabEx) for NASA in the 2030s or 2040s. It would scan exoplanets over a wide range of optical and near-infrared wavelengths for signs of oxygen and water vapour.
Casting a wide search for ET won’t be easy and it won’t be cheap, but it will surely be transformative. Even if astrobiologists find nothing, that knowledge will tell us how special life is here on Earth. And any kind of success will be Earth-shattering. Finding terrestrial-style bacteria on Mars would tell us we’re not alone. Finding methane-swimming organisms on Titan would tell us, even more profoundly, that ours is not the only way to make life. Either way, we Earthlings will never look at the cosmos the same way again.
This article was originally published at Aeon and has been republished under Creative Commons.
“You look at the night sky — virtually all of those stars have planets,” Rosenberg said in an exclusive interview with Futurism. “Maybe one out of five has it at just the right zone where there’s liquid water. And so we know there are a lot of places that there could be life. Now the big question is, are they actually trying to make contact, or do they want us to try?”
METI’s stance is that we should assume the latter, and the collection of scientists have taken it upon themselves to reach out to any potential alien civilizations. In fact, the next transmission planned for next year. However, there have long been voices opposed to this strategy — perhaps the most prominent of which being Stephen Hawking.
Hawking, a noted physicist and author, supports the search for aliens, but regularly cautions against attempting contact. Hawking argued in “Stephen Hawking’s Favorite Places,” a video on the platform CuriosityStream, that aliens could be “vastly more powerful and may not see us as any more valuable than we see bacteria.”
Paying Our Dues?
These are not warnings that Vakoch takes lightly. “Well, when Stephen Hawking, a brilliant cosmologist, has said, ‘whatever you do, don’t transmit, we don’t want the aliens to come to Earth,’ You’ve got to take it seriously,” Vakoch told Futurism.
But there’s one key point that Hawking really doesn’t seem to take into consideration in this assessment, Vakoch said.
It’s the fact that every civilization that does have the ability to travel to Earth could already pick up I Love Lucy. So we have been sending our existence into space with radio signals for 78 years. Even before that, two and a half billion years, we have been telling the Universe that there is life on here because of the oxygen in our atmosphere. So if there’s any alien out there paranoid about competition, it could have already come and wipe us out. If they’re on their way, it’s a lot better strategy to say we’re interested in being conversational partners. Let’s strike up a new conversation.
It’s Vakoch’s belief that humanity’s first contact with alien life will occur within our lifetimes. But even if it does not, he believes the METI project will be foundational to any relationship our world builds with others.
“Sometimes people talk about this interstellar communication as an effort to join the galactic club. What I find so strange is no one ever talks about paying our dues or even submitting an application. And that’s what METI does,” Vakoch said. “It’s actually contributing something to the galaxy instead of saying gimme gimme gimme me. What can we do for someone else.”
One of the most well known quotes regarding life in the universe aside from our own is from Sir Arthur C. Clarke, who once said: “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”
We know next to nothing about intelligent alien life, including the probability of their existence. Yet, even the smartest people among us believe we’ll make contact, and sooner rather than later. When we asked our readers when this life-changing event could occur, we learned almost 50 percent believe (or at least hope) we’ll make first contact before 2040. 27 percent think it’ll happen even sooner, in the 2020s. Developments in technology have allowed us to better understand our universe and what’s in it, including the discovery of exoplanets that could contain alien life.
Making the First Move
We haven’t just been sitting around over the years hoping aliens will reach out to us first. We’ve made a number of attempts to call out to the stars, and have even made it possible for other intelligent species to find our home planet; plans to talk to those residing off-world have been around for much longer than we may think.
In 1820, astronomer Joseph Johann von Littrow proposed carving a series of large squares, circles, and triangles into the Sahara Desert, filling them with kerosene, then lighting them at night in an attempt to communicate with Mars. In 1896, Nikola Tesla suggested his device to transmit electricity without wires could be used to reach out to Mars.
More recent attempts like the Voyager 1 and Voyager 2 both contain pulsar maps leading to our location, and the Aceribo Message was beamed into space in 1974. As promising as they may sound, Frank Drake, creator of the original pulsar map, has said it’s unlikely the maps aboard the probes will ever be found, since they take half a million years to travel from one star to another, and they’re not aimed at anything specific. It’s equally unlikely the Aceribo Message will even get a response, though that hasn’t stopped others from sending messages of their own into space, like the European Space Agency did late last year.
Those are just simple messages and unmanned spacecraft, though. Surely people would be able to get it done sooner if they ventured out into the great unknown?
Unfortunately, even popular astrophysicist Neil deGrasse Tyson believes that to be far off. During a Reddit AMA in April, he explained that such contact between ourselves and other intelligent organisms is more than 50 years away.
“No. I think they (we) might all be too far away from one another in space and possibly time,” he said. “By complex, I’m presuming you mean life other than single-celled organisms. Life with legs, arms, thoughts, etc. It’s all about our capacity to travel interstellar distances. And that’s surely not happening in the next 50 years. Not the rate things are going today.”
The Best Way to Communicate
There’s no surefire way to reach out to alien life or to be ready when they call to us. That said, we can be as prepared as possible, and continue sending messages in various languages, but the latter is the hardest part. As New Atlas explains, such a message has to be recognized as harmless, but one worth paying attention to. More importantly, it has to be understandable — but how do you make something understandable when you don’t know the full extent of what an undiscovered form of life can comprehend? Messages like the aforementioned pulsar map and Aceribo message meet the requirements, but sending more messages like them has been met with opposition.
Physicist Stephen Hawking, who, while not against the idea of there being other life in the universe, believes we shouldn’t be so eager to let them know we’re here and what we’re capable of. He proposed the idea that whatever species we engage with could be “vastly more powerful and may not see us as any more valuable than we see bacteria.” This could lead to an unfavorable situation, potentially leading to our extinction or being conquered.
Fellow physicist Michio Kaku has also spoken on how to contact alien life, but suggests we may simply be unable to, due to our current technology and understanding of the universe. He once compared us communicating with intelligent alien life to ants trying to connect with us.
“If ants in an ant hill detect a 10-lane superhighway being built near them, would they understand how to communicate with the workers? Would they assume that the workers communicate only on ant frequencies? In fact, the ants are so primitive that they would not even understand what a 10-lane superhighway was.”
Regardless of our place in the universe, it’s clear that many believe we’re not alone, and that we’re on track to our first interaction. Now, it’s just a matter of being prepared, and making the most of it when it does happen.
For retired astrophysicist Daniel Whitmire, currently a mathematics professor at the University of Arkansas (UARK), humanity is typical. Not exactly in the sense that we’re ordinary; we’re typical in a statistical sense, following a concept in modern cosmology called the principle of mediocrity. This principle suggests that in the absence of evidence to the contrary, we should consider humanity to be a typical member of a certain reference class.
This was Whitmire’s conclusion, in a study published in the International Journal of Astrobiology, when he revisited his thoughts on the Fermi Paradox — that we haven’t encountered alien life, despite the high probability of it existing — and again asked if there’s alien life out there. With all the billions of stars in billions of galaxies, chances are there’s bound to be other intelligent life in the cosmos. So, where are they?
“I used to tell my students that by statistics, we have to be the dumbest guys in the galaxy,” Whitmire said in a UARK press release. “After all, we have only been technological for about 100 years, while other civilizations could be more technologically advanced than us by millions or billions of years.”
But Whitmire changed his mind on this concept based on two observations: Firstly, that humanity was the first technologically advanced civilization that evolved on Earth, and we’re currently in our early technological development. (“Technological,” here, is to be understood as biological species that developed electronic devices and are capable of significantly changing the planet.)
On the surface, this may seem like an obvious observation. However, based on the Earth’s habitable time span — from around 5 billion years ago, and for an estimated billion years in the future — it would have been possible for other technological civilizations to precede us on this planet. The thing is, there’s no geologic record that shows someone else came before us. “We’d leave a heck of a fingerprint if we disappeared overnight,” Whitmire said.
Anybody Out There?
But what about life outside of the Earth? Following the same principle of mediocrity, technological civilizations that lasts millions of years or longer are atypical, Whitmire says. If one considers a bell curve of all supposedly extant technological civilizations in the universe, humanity would fall in the middle 95 percent.
If that is the case, the lack of communication from similar civilizations around us does not bode well. Whitmire explains the silence of the cosmos as a product of how typical technological civilizations work: They usually go extinct after attaining technological knowledge. This is the same explanation held by other scientists, and one even suggests that we should look for traces of alien technology instead of alien life.
The “Great Filter” hypothesis is another possible explanation. It suggests that before any life in the universe becomes technological or before technological life goes beyond the bounds of its own planet, it had to overcome some extremely difficult evolutionary threshold. Some even think that climate change is humanity’s great filter.
For resident “Science Guy” Bill Nye, the Fermi Paradox should push humanity to explore further. The reason why we haven’t found intelligent extraterrestrial life or even simple alien life is because we haven’t been looking hard enough. There’s still a big chance that they’re somewhere out there.
Yet these theories assume that we’re not a typical representative of life in the cosmos. “If we’re not typical then my initial observation would be correct,” Whitmire said. “We would be the dumbest guys in the galaxy by the numbers.”
We’re already searching for intelligent life elsewhere in the galaxy — any life, for that matter — and even signs of alien technologies. If advanced lifeforms were also trying to make contact, a galactic communications network might someday be possible. Therefore, maybe we should be focusing first on the ability to communicate with advanced civilizations in other galaxies. Duncan Forgan, of the University of St. Andrews in the UK, thinks so. If we can manipulate the light from our sun as a beacon, either passing massive sheets in front of it to send signals, or changing how the Earth’s transits appear to distant worlds, we might be able to realize our dreams of a galactic community.
Forgan has just created a new simulation that shows it would require a minimum of 300,000 years to build such a communications network around the Milky Way galaxy, and that’s assuming there would be 500 or so civilizations that were technologically advanced enough to visibly manipulate their planet’s transit (so clearly getting started now makes sense).
For this kind of contact to work, we’d need to construct a relay network throughout the galaxy, avoiding celestial obstacles as we went. “If you want to communicate with someone on the other side of the galactic center, there’s lots of stuff in the way — dust, stars, a big black hole — so you can take the long way around using the network,” Forgan told New Scientist.
Searching For Extraterrestrial Signals
In order to detect signals that could be from extraterrestrial lifeforms, you really need the serendipity of being in the right place at the right time; you’d need to be facing the right way at a time when nothing (such as another planet) was obscuring the signal. Because planets orbit between us and their stars predictably, we could find them and communicate — but only if their orbit was aligned to be visible to us in front of its sun, and the inhabitants of the planet were advanced (and friendly) enough to change the planet’s transits to look like a signal.
However, what’s possible isn’t always likely, and this is one of those times. Professor and Harvard University astronomy department chair Avi Loeb told New Scientist that the construction of this kind of massive orbiting object was an unlikely occurrence: “Once a civilization is advanced enough to have the technology to build megastructures, it’s much more likely to leave its planet,” Loeb commented. “Each signal would take thousands of years to travel back and forth. In cosmic time that may not be that long, but you need patience.”
While we have existing projects looking for planets passing before stars, such as the Kepler space telescope (which would mean we’d see planets if they were trying to reach out and be seen), there would be additional hurdles involved in creating a cooperative galactic network. As New Scientist points out, the interstellar politics alone are likely to be daunting — particularly given how complex international politics are on Earth.
The Drake Equation attempts to quantify how likely we are to find intelligent alien life.
It takes all of the variables required for an intelligent civilization to exist AND send out communication signals, then multiplies them together.
The values of the variables on the left side of the equation are skyrocketing the more we explore the universe with telescopes and satellites. We’ve found far more star systems and planets capable of hosting life than we ever thought possible. Some estimates are as high as 60 billion planets in the Milky Way!
But the N value (the estimated number of alien civilizations in our galaxy capable of communication) must still be small because…well…we haven’t found them yet!
That begs that question — which of the variables on the right side, the unknowns, are the great filters causing that small N value?
The most critical variable to us on Earth is the last one. L is the length of time civilizations release detectable signals into space.
If L is responsible for the small N value, it could mean that species don’t often last long enough to create signals, let alone receive them. It would then stand to reason that the near-term destruction of our species is statistically probable.
SETI researchers hope that, instead, the great filter is behind us. Perhaps the emergence of intelligent life is the rare occurrence rather than how long those lifeforms survive.
Or maybe the Drake Equation is incomplete.
Maybe they have some Star Trek-esque ideal of never meddling with the growth of early-stage civilizations.
Maybe they are out there listening, but they’re so far away that our signals won’t reach them for centuries, and their replies will take just as long to hit our digital ears.
Maybe they’re so much more advanced that we’re just not that interesting to them.
…or maybe we’re one day away from receiving a reply.
Neil deGrasse Tyson is one of the (if not the) most well-known astrophysicists. He is also an accomplished author and science communicator/entertainer, and the Frederick P. Rose Director of the Hayden Planetarium at the Rose Center for Earth and Space in New York City. Also, he doesn’t think that we are alone in the universe.
Appearing on C-SPAN’s In Depth, he explained how the chemistry of life makes it extremely unlikely that Earth is the only place in the universe where life has formed. He said, “Whatever happened on Earth, it’s not likely to be rare or unique. Because carbon chemistry, on which life is based, is the most fertile kind of chemistry there is. And carbon is abundant across the universe.”
However, Dr. Tyson does separate the questions of whether there is life elsewhere in the universe, and if intelligent life exists, from if we have been visited by any intelligent life. “What the UFO community puts forth as evidence is weak on a level that, in any scientific circle, would be kicked out of the lab room.”
The basis of this argument boils down to the foundations of the scientific method. Eyewitness testimony is nowhere near enough evidence to support a claim as fantastical as alien visitors. Current evidence of chemistry is enough to allow scientists to assert that there is life on other planets, but that evidence does not extend as far as intelligent life.
St. Petersburg College astronomer Antonio Paris believes that a comet called 266P/Christensen, uncatalogued at the time that the “Wow!” signal was first discovered, may actually have been the signal’s source. However, not all astronomers agree — including Jerry Ehman, the astronomer who discovered the signal in 1977. “We do not believe the two-comets theory can explain the Wow! signal,” Ehman told Live Science on June 12.
Ehman reviewed Paris’s work with Robert Dixon, the director of the radio observatory at The Ohio State University. The team agreed on two major problems with the conclusions that Paris drew. First, the signal didn’t repeat. Second, it appeared for a very short time. Ehman also noted that the configuration of the Big Ear telescope should have allowed for a repeat if the source was a comet; instead, there was only one, as if the source was abruptly cut off. The telescope had two “feed horns,” and each offered a slightly different field of view.
“We should have seen the source come through twice in about 3 minutes: one response lasting 72 seconds and a second response for 72 seconds following within about a minute and a half,” Ehman told Live Science. “We didn’t see the second one.”
The frequency of transmission is also problematic. SETI senior astronomer Seth Shostak argues that comets wouldn’t generate sufficient hydrogen to create the signal. “I don’t think anyone ever found such emission from comets,” Shostak told Live Science.
So, does this lend credence to the theory that the “Wow!” signal was sent by aliens?
Both the most cynical person on Earth and the world’s greatest optimist could easily look at everything around them and ask: could this truly be all there is in the universe? Whatever your reason for posing the question, you may have an answer sooner than you think — and that answer is likely to be “no.” Science writer and comedian Ben Miller posits in his book The Aliens Are Coming! The Extraordinary Science Behind Our Search for Life in the Universe that one of the most powerful forces shaping science today is the growing search for life in the universe fueled by the belief that we are not alone. He believes that because of our current technologies, we’ll know about life on the Earth-like planets closest to us within the next ten years.
It’s easy to see why he thinks so. Scientists have identified an exoplanet that they’ve described as the best candidate for life as we know it — perhaps an even more important a target for planet characterization within habitable zones in the future than either Proxima b or TRAPPIST-1, and these have also recently been discovered. Speaking of Proxima b, the James Webb Telescope is likely to give us the images that will clarify its potential for supporting life, as it will do for other exoplanets.
In recent months scientists have stated that the fast radio bursts we’ve intercepted from outer space may well be evidence of alien life. Now they’re working to discern whether alien technology could be their source. Scientists also now believe that life might exist on Europa, one of Jupiter’s four Galilean moons. Recently, NASA’s plans to send a lander in search of biosignatures that might signal the presence of extraterrestrial life within its warm core have sprung into action; Europa may be home to a subterranean ocean, making it an ideal place to search for alien life.
In 2016, researchers made improvements to the Atacama Large Millimeter/submillimeter Array that could make finding water on celestial bodies easier. These improvements were specifically directed toward the ongoing search for alien life, as was the partnership between Breakthrough Initiative to find alien life and the National Astronomical Observatories of China. China’s team uses the 488 meter (1,600 foot) FAST telescope, and now it is being used in partnership with the world’s other largest radio telescopes, including the Parkes Observatory in Australia and the Green Bank Telescope in the US, to seek out extraterrestrial life. In 2016 scientists also adopted more accurate methods for studying gravitational pull of distant stars, making it easier to gather data on the size and brightness of the star, the likelihood of water oceans, and possibility of life being present.
An Utterly Changed Humanity
Why are we so enthralled with this search for other life in the universe? It’s far more than an AV geek, sci-fi con hangover, if that’s your suspicion. Contact could mean extraordinary things for humanity if it happens soon — some of the possibilities are daunting, but most of them are promising.
Stephen Hawking is one of the best-known and most reputable voices who cautions against making first contact with alien life. His argument is simply that we have no way of knowing what’s out there, and that, historically speaking, as more advanced civilizations have come into contact with less advanced cultures, the latter has typically been oppressed and aggressed against, the former seeing it as less valuable. However, it’s worth noting that when we speak historically we are, by necessity, limited to our own recorded human history. What we’re observing may not be a pattern common to all life; it may simply be a pattern common to human cultures.
In contrast, the SETI (Search for Extra Terrestrial Intelligence) Institute is populated by people who feel we have little, if anything, to lose by seeking out other forms of life. SETI has now given birth to METI International (Messaging Extra Terrestrial Intelligence), which is actively seeking out contact. Douglas Vakoch, a professor in the Department of Clinical Psychology at the California Institute for Integral Studies and the president of METI International, strongly disagrees with Hawking. He thinks it is illogical to hide our existence as a species since we have already leaked transmissions from radio and television broadcasts in the form of electromagnetic radiation for almost 100 years. Vakoch concludes that any culture with the technological sophistication to master interstellar travel can already perceive our leaked signals, and are therefore already aware of us, waiting for us to make the first move.
METI, led by Vakoch, is now working to target star systems within 20 or 30 light-years with repeat messages as part of an effort to accumulate data in order to test the Fermi Paradox and the Zoo Hypothesis. Ideally, within a few decades, Vakoch and his team hope that they will generate a testable hypothesis with enough data and standard peer-review methods.
As for Miller, he’s not on Team Hawking, and thinks that the benefits of contact outweigh the risks. The potential to learn about advanced technology for space travel, repairing our planet’s environment, and many other applications is an obvious benefit to contact. For Neil deGrasse Tyson, the big benefit to contact is more profound: right now, our understanding of life is extremely limited, and that is because we only have our own, terrestrial sample of life to study. The notion that we have an understanding of the tremendous diversity of life is somewhat silly when you think of it in this context; our entire set of observations all share a single origin and an encoded existence that transmits heredity and mediates replication via nucleic acids.
Our current understanding of life is too much like the infamous legal definition of pornography — the classic “I know it when I see it” — which, for Tyson, lacks scientific rigor (and to clarify, he is not responsible for that icky analogy). But our explorations of the galaxy to find contact with other forms of life could give us other examples and samples, and a truer sense of what life truly is. This kind of knowledge has the potential to change everything else we think we know, most likely for the better.
If mankind were contacted by an alien race, how would the world react? How would people change?
In his novel, Contact, the late, great astronomer Carl Sagan explores this fascinating question.
I recently had the pleasure of reading Contact, and one of the aspects I most admired about it was Dr. Sagan’s humble suggestion that communication with an alien race would compel mankind to reassess its internal conflicts and prejudices.
Imagining Earth’s Reaction to News of Alien Life
“By now, the news of the Message from Vega had reached every nook and cranny of the planet Earth. […] Amidst the sectarian commentary, there was also—all over the world, it was now apparent—a sense of wonder, even of awe. Something transforming, something almost miraculous was happening. The air was full of possibility, a sense of a new beginning.
There were still political conflicts, some of them—like the continuing South African crisis—serious. But there was also a notable decline in many quarters of the world of jingoist rhetoric and puerile self-congratulatory nationalism. There was a sense of the human species, billions of tiny beings spread over the world, collectively presented with an unprecedented opportunity, or even a grave common danger. To many, it seemed absurd for the contending nation states to continue their deadly quarrels when faced with a nonhuman civilization of vastly greater capabilities.
For decades after 1945, the world stockpile of strategic nuclear weapons had steadily grown. […] The time came when there were more than 25,000 of them on the planet, ten for every city. […] But finally the world came to its senses. […] the Americans and the Russians undertook to diminish their strategic arsenals down to a thousand nuclear weapons each. […] Britain, France, and China agreed to begin reducing their arsenals once the superpowers had gone below the 3,200 mark. The Hiroshima Accords were signed, to world-wide rejoicing, next to the famous commemorative plaque for the victims in the first city ever obliterated by a nuclear weapon: ‘Rest in peace, for it shall never happen again.’“
Sagan speculates that an extraterrestrial message would have the effect of revealing to mankind the folly of its divisions against itself. He seems to suggest that our national boundaries, in the face of a situation affecting the entirety of our small, blue world, would appear as little more than arbitrary lines drawn in the sand, reducing our obstinate and ego-driven political conflicts to little more than unreasonable disputes among siblings, and ushering in a newfound spirit of cooperation and peacemaking.
A beautiful proposition, to be sure. The subtextual message to be drawn from this is that we would be wise to reach these realizations on our own, and that sometime (probably in the not-too-distant future) we must. In the face of looming environmental crises and continuing war and conflict in 2013, Sagan’s message remains supremely poignant. Understanding our inherent unity and shared destiny as natives of Earth should not require an event of galactic magnitude. In the coming decades, it will be our responsibility to find in our hearts a Sagan-esque cosmic perspective, if we are to band together and confront the sizable challenges facing our planet.
Later in the novel, Sagan discusses the effect of viewing the Earth from the perspective of one who is orbiting it in space:
“It wasn’t hard to imagine a time when the predominant loyalty would be to this blue world, or even to the cluster of worlds huddling around the nearby yellow dwarf star on which humans, once unaware that every star is a sun, had bestowed the definite article: the Sun. It was only now, when many people were entering space for longer periods and had been afforded a little time for reflection, that the power of the planetary perspective began to be felt. A significant number of these occupants of low Earth orbit, it turned out, were influential down there on Earth.”
The Overview Effect and the “Pale Blue Dot”
One is reminded here of what has been called “the overview effect,” which refers to the profound shift in perspective that is said to be experienced when one views the Earth from space.
There is a wonderful documentary, just under 20 minutes long, that shares the life-changing stories of astronauts who have seen the Earth from the outside: watch it here if you’re interested.
Sagan was certainly someone who believed in the transformative power of viewing the Earth from a different vantage point. One of his most famous quotes was made in reference to the image below, dubbed the “Pale Blue Dot” image, which is also the title of Sagan’s book that discusses the image.
In the orange-ish beam of light on the right side of the image, you’ll notice a tiny speck. That speck is Earth, our home, as seen from Voyager 1 in 1990. Upon seeing this image, Carl Sagan was inspired to reflect on its significance. It seems only fitting to here include Sagan’s eloquent and moving thoughts on the “Pale Blue Dot“:
“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.
The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there—on a mote of dust suspended in a sunbeam.
The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner—how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.
Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.
It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.”
Carl’s Message is Clear
Carl Sagan’s life was dedicated to the advancement and betterment of our species. Though he is perhaps thought of first as one who spent his life gazing outward, his writings reveal a strong commitment to humanitarian concerns.
This begins with each of us. When we practice kindness, acceptance, and non-aggression in our daily lives, we do the work of slowly creating that of which so many have dreamt: a loving and non-violent world.His advice to us, like that of so many great teachers and leaders of history, is simple and unmistakable. From beyond the grave, he urges us to band together, to see through our artificial and constructed differences, to embrace one another as members of a single global community. He suggests in utter seriousness that the future of our planet and species depend on this transformation of heart and mind. Sagan left the world a wonderful legacy, and we should honor him by striving to become what he envisioned: compassionate, peaceful, and unified.
“Every one of us is, in the cosmic perspective, precious. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another.”
For those familiar with indie space game Stellaris, one of the key moments before encountering ancient intelligent life is finding traces of technology. While the game is a work of science fiction, the concept isn’t outlandish to those behind the real life search for extraterrestrial life (SETI). According to astronomer Jason Wright, discovering traces of advanced technology, termed technosignatures, from alien civilizations is just as important as looking for biosignatures. He outlines his theory in new paper published online, and while he doesn’t claim there’s existing, direct evidence of aliens, he does wonder if we’re just not looking hard enough – or for the right signs.
“There is zero evidence for any prior indigenous technological civilizations,” Wright told Gizmodo. “My paper asks, have we completely foreclosed the possibility, or is there a chance that there could be some evidence we overlooked? [And] if we have overlooked something and we find it in the future, what are the chances it could have come from a prior indigenous technological species versus an interstellar one?”
Currently, the hunt for aliens is focused on finding even the smallest signs of life, or mechanisms that could support life (most notably, the presence of water). These are all good, of course, but Wright suggests that we might also start looking for technosignatures from ancient alien civilizations.
“A ‘technosignature’ is evidence of technology,” he said, which potential could have been left behind by some long-gone alien civilization. In his paper, he explained his point further: “We might conjecture that settlements or bases on [rocky moons or asteroids] would have been built beneath the surface for a variety of reasons, and so still be discoverable today.”
However, despite the odds seemingly in our favor, we really haven’t found any such example of alien life out there — yet. Fermi Paradox, yes? But, could it be that we’ve been looking at the wrong things? Or are we simply not looking hard enough?
Wright just wants us to explore all possible options: “While all geological records of prior indigenous [extraterrestrial] technological species might be long destroyed, if the species were spacefaring there may be technological artifacts to be found throughout the Solar system.”
One of humanity’s most pressing questions is, “Are we alone in the universe?” Scientists have conducted countless studies in an attempt to answer the question, some coming up with data that supports a no — but others, like a recent study from the University of California Berkeley, may well lean more toward a yes.
Researchers from the UCB analyzed scans of 5,600 nearby stars throughout the Milky Way in search of signs of laser beams. They studied scans taken by the Keck telescope in Hawaii between 2004 and 2016 looking for beams spanning the most visible wavelengths.
The stars examined were estimated to host around 2,000 planets similar to Earth in size and temperature that could, theoretically, support alien lifeforms. However, apparently none of these lifeforms are — as the researchers wrote in their submission — “beaming optical lasers toward us.”
Of course, a lack of evidence does not disprove the existence of alien life. It’s possible that otherworldly civilizations are not yet advanced enough to use lasers. Or it could be that they have lasers, but are not using that particular tool to try and interact with other worlds — which is, by the way, the boat humans here on Earth are in.
Light at the End of the Tunnel
It’s also worth noting that the study examined just a tiny sliver of our galaxy. To put this in perspective, there are an estimated 300 billion stars in the Milky Way, and these are estimated to host nearly 9 billion habitable, Earth-size planets. If there are advanced civilizations on any of these planets sending us light shows, the scans used for this study would almost certainly have missed them.
In fact, the researchers determined that their study could only account for over 0.1 percent of warm, Earth-sized planets in the Milky Way — that are not, consequently, sending laser signals into space. That means there’s still 9 million planets they haven’t ruled out yet.
The researchers note that a bigger study of interstellar laser signals will be performed by the Breakthrough Listen Initiative, which is hailed as the largest scientific research program ever aimed at finding evidence of alien civilizations. The 10-year study will examine 1 million of the closest stars in the Milky Way— including star types that were overlooked in the Berkeley study, like brown dwarfs.
Even if this study does not yield proof of extraterrestrial life, there are other signs we can look for besides lasers. Beyond that, there’s always the Andromeda galaxy.
Only a few decades ago, the thought of any alien planets existing in the reaches of space were just hypothetical ideas. Now, we know of thousands of such planets – and today, scientists may have discovered the best candidate yet for alien life.
That candidate is an exoplanet orbiting a red dwarf star 40 light-years from Earth—what the international team of astronomers who discovered it have deemed a “super-Earth.” Using ESO’s HARPS instrument and a range of telescopes around the world, the astronomers located the exoplanet orbiting the dim star – LHS 1140 – within its habitable zone. This world passes in front of its parent stars as it orbits, has likely retained most of its atmosphere, and is a little larger and much more massive than the Earth. In short, super-Earth LHS 1140b is among the most exciting known subjects for atmospheric studies.
Although the faint red dwarf star LHS 1140b is ten times closer to its star than the Earth is to the Sun, because red dwarfs are much smaller and cooler than the Sun is, the super-Earth lies in the middle of the habitable zone and receives around half as much sunlight from its star as the Earth does.
“This is the most exciting exoplanet I’ve seen in the past decade,” lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics said in an ESO science release. “We could hardly hope for a better target to perform one of the biggest quests in science — searching for evidence of life beyond Earth.”
Life As We Know It
To support life as we know it, a planet must retain an atmosphere and have liquid surface water. When red dwarf stars are young, they emit radiation that can damage the atmospheres of planets around them. This planet’s large size indicates that a magma ocean may have existed on its surface for eons, feeding steam into the atmosphere and replenishing the planet with water until well within the time the star had cooled to its current, steady glow. The astronomers estimate the planet is at least five billion years old, and deduce that it has a diameter of almost 18,000 kilometers (11,185 mi)— 1.4 times larger than that of the Earth. Its greater mass and density implies that it is probably made of rock with a dense iron core.
Two of the European members of the team, Xavier Delfosse and Xavier Bonfils, stated in the release: “The LHS 1140 system might prove to be an even more important target for the future characterization of planets in the habitable zone than Proxima b or TRAPPIST-1. This has been a remarkable year for exoplanet discoveries!”
Scientists expect observations with the Hubble Space Telescope will soon allow them to assess how much high-energy radiation the exoplanet receives, and further into the future — with the help of new telescopes like ESO’s Extremely Large Telescope and the James Webb Telescope — detailed observations of the atmospheres of exoplanets will be possible.
Lord Martin Rees, Astronomer Royal and University of Cambridge Emeritus Professor of Cosmology and Astrophysics, believes that machines could surpass humans within a few hundred years, ushering in eons of domination. He also cautions that while we will certainly discover more about the origins of biological life in the coming decades, we should recognize that alien intelligence may be electronic.
“Just because there’s life elsewhere doesn’t mean that there is intelligent life,” Lord Rees told The Conversation. “My guess is that if we do detect an alien intelligence, it will be nothing like us. It will be some sort of electronic entity.”
Rees thinks that there is a serious risk of a major setback of global proportions happening during this century, citing misuse of technology, bioterrorism, population growth, and increasing connectivity as problems that render humans more vulnerable now than we have ever been before. While we may be most at risk because of human activities, the ability of machines to outlast us may be a decisive factor in how life in the universe unfolds.
“If we look into the future, then it’s quite likely that within a few centuries, machines will have taken over—and they will then have billions of years ahead of them,” he explains. “In other words, the period of time occupied by organic intelligence is just a thin sliver between early life and the long era of the machines.”
In contrast to the delicate, specific needs of human life, electronic intelligent life is well-suited to space travel and equipped to outlast many global threats that could exterminate humans.
“[We] are likely to be fixed to this world. We will be able to look deeper and deeper into space, but traveling to worlds beyond our solar system will be a post-human enterprise,” predicts Rees. “The journey times are just too great for mortal minds and bodies. If you’re immortal, however, these distances become far less daunting. That journey will be made by robots, not us.”
But what if Rees is correct and humans are on track to self-annihilate? If we wipe ourselves out and AI is advanced enough to survive without us, then his predictions about biological life being a relative blip on the historical landscape and electronic intelligent life going on to master the universe will have been correct—but not because AI has turned on humans.
Ultimately, the idea of electronic life being uniquely well-suited to survive and thrive throughout the universe isn’t that far-fetched. The question is, will we survive alongside it?
Although TRAPPIST-1 is 40 light-years away, its remarkable similarities to our own solar system make the discovery very exciting to scientists. Of all the solar systems we know of, we’ve never found one with seven planets — let alone multiple Earth-sized planets. TRAPPIST-1’s three habitable planets have density measurements that make them appear to be Earth-like worlds.
Given what TRAPPIST-1’s current configuration looks like, the planets located in the habitable zone or “goldilocks zone” could have water — at least theoretically. However, since its solar system’s sun is smaller than ours, the planets would require a tighter orbit in order to support surface water.
Armed with insights we’ve gathered about our own solar system in recent decades, we have the knowledge and resources to study TRAPPIST-1 — and possibly find life beyond our own planet.
Life Beyond Earth
Scientists also believe that some of the planets in TRAPPIST-1 are “tidally locked” to their star. That means one side of the planet constantly faces their sun, bathing it in perpetual daylight, while the other side is always in the dark. While that doesn’t sound much like the life we know on our planet, experts believe it wouldn’t completely negate the possibility of life: what really matters is the atmosphere.
We won’t have to wait too long to gain further insight into kind of atmosphere these planets have: once the James Webb Space Telescope launches in October of next year, scientists will be able to study the planets more in-depth. Our knowledge of how tidally locked planets in our own solar system manage such extreme temperatures — based on what we’ve already learned from Neptune and Jupiter — will also lend itself to a better understanding of how the TRAPPIST-1 planets work.
Granted, everything that we know about life stems from our understanding of life on Earth—where we experience both day and night. It’s wholly possibly that in planets where a diurnal cycle isn’t the norm, life develops very differently.
But as Dr. Jessie Christiansen, an astronomer at the NASA Exoplanet Science Institute at the California Institute of Technology, notes while speaking to the Christian Science Monitor, we could liken this to conditions some creatures on our planet know well: the life aquatic. “If you think about life in the deep ocean,” Dr. Christiansen says, “it has evolved without a true diurnal cycle.”
Here on our own planet, we are still constantly surprised by life discovered in sea floors, icy climates, deep caves, and other extreme settings. So, that being said, the idea that life could exist in TRAPPIST-1 shouldn’t be too hard to fathom.
It’s one of the most pressing questions in science: is there alien life somewhere out there within the great wide demesnes of the universe—beyond the homely, terrestrial sort that we’re all familiar with?
We’re still searching for the answer, but it seems that each day brings word of some new exoplanetary discovery that may at last resolve the issue—our technology has evolved to the point where we can now detect Earth-sized (note the distinction between “Earth-sized” and “Earth-like”) exoplanets residing in the habitable zones of their parent stars.
But are we restricting ourselves—unnecessarily—with the fetters of a geocentric prejudice? The circumstellar habitable zone (HZ) merely represents that part of a planetary system where temperatures are conducive to the existence of liquid water—in other words, precisely where the Earth currently resides in the Solar System. Certainly, with everything being equal, a planet with these conditions in a star’s HZ would be habitable to terrestrial life as we know it—but whoever said that’s all we’re looking for? Furthermore, we know that the HZ isn’t static in time; as a main sequence star evolves, its temperature increases, and the zone of habitability sweeps further outward—which is something to consider for highly-evolved, red giant stars, as a recent study has shown.
Putting aside the question of completely alien life, founded upon chemical organizations radically unlike anything we know, it’s not even clear that terrestrial-type life could only evolve upon an Earth-like planet within its star’s HZ. That’s where studying the icy moons of Jupiter and Saturn becomes important.
Ever since the Voyager probes winged their way galaxy-ward, there’s been a great deal of speculation that Jupiter’s second moon, Europa, might harbor a warm, liquid ocean beneath its piebald shell of red-and-white ice; recent observations with the Hubble Space Telescope even suggest some of that water is escaping into space, in the form of geysers—akin to what we see on Saturn’s moon Enceladus.
The Ice-Covered Ocean
The existence of such an ocean on Europa is attributable to the intricate celestial mechanics of the Galilean Moons; this remarkable dance—choreographed across billions of years between Io, Ganymede, Europa and the prodigious mass of Jupiter—has squeezed and warmed Europa’s mysterious innards through the action of tidal flexure. It’s a bit like what’s happened to twisted, volcanic little Io—only with a far happier and less Dantean result.
Now, it doesn’t necessarily follow that a motley assortment of marine monsters has evolved in Europa’s putative subglacial world-ocean—though we all prefer to believe that’s exactly the case. But there’s certainly reason enough to be hopeful.
Life on Earth, for instance, needs water and a source of energy—the Sun, in most cases. But it’s also true that certain organisms, particularly in the deep oceans, derive their energy from purely non-solar sources; it’s even possible that the earliest life on Earth was of just such a type, at a time when the Sun’s radiation was far weaker than it is today.
A recent study has shown that an exothermic chemical reaction known as “serpentinization,” whereby saltwater reacts with rocky minerals to produce heat and hydrogen, may be as common on Europa as in terrestrial oceans. Furthermore, the blistering radiation of Jupiter may be enough to separate oxygen atoms from water molecules in the moon’s icy mantle, with the oxygen then cycling deep into the interior. If correct, it means all the ingredients for a thriving ecosystem are theoretically in place; all that’s needed is the spark of life—unfortunately, ascertaining the likelihood of that happening is beyond our statistical models.
“Observations of Europa have provided us with tantalizing clues over the last two decades, and the time has come to seek answers to one of humanity’s most profound questions,” says John Grunsfeld, associate administrator of NASA’s Science Mission Directorate.
Regardless of what the probe discovers, it’s about time we start expanding our definition of what the “habitable zone” really means—in our own Solar System, as in the myriad exoplanetary systems swimming daily within our ken.
In the hunt for a celestial body that could host life (specifically, life like that found on Earth), scientists have typically looked for planets with surfaces similar to our own — about the same temperature, same chemical makeup, and, ideally, with liquid water like that from which we evolved. Now, a whole new group of space objects has joined the list of potential life-supporting hosts, and they don’t have a planet-like surface at all.
Researchers from the University of Edinburgh in the United Kingdom have proposed that we look for life in the upper atmospheres of cold brown dwarfs. These “failed stars” have the same elements found in traditional stars, but they lack the mass to ignite. Somewhere between the size of a planet and a star, they can boast atmospheres that hover around temperatures that would be considered comfortable on Earth and with about the same pressure levels.
“You don’t necessarily need to have a terrestrial planet with a surface,” Jack Yates, a planetary scientist who led the study, told Science.
The Hunt Is On
This development would open up a whole new arena in the hunt for extraterrestrial life, just maybe not life that looks like we do.
Microbes like those that lurk high above our own atmosphere could be discovered, or perhaps we’d find some of the sky plankton Carl Sagan coined “sinkers.” “Floaters,” organisms that manipulate their body pressure to rise and fall within an atmosphere, could also be hovering above cold brown dwarfs.
Though we only know of a handful of cold brown dwarfs right now, about 10 of those are likely to be within 30 light-years of Earth. With the James Webb Space Telescope (JWST) set to launch in just over a year, we may have our answer as to whether these bodies host life sooner rather than later.
Not only would it be a huge discovery if they do, it would also throw out the window our preconceived notions about where to look for life beyond our planet.