We are searching data for your request:
Upon completion, a link will appear to access the found materials.
I'm not asking about the possibility of formation of life on other planets instead has there been any real evidence of life(such as micro organisms or even very basic structures) that might suggest an evolutionary path(for example from asteroids that hit the earth or planets and other objects in the solar system)?
No, there has been no evidence found of extraterrestrial or off-Earth life, at least as publicly-shared information. Via NASA:
No life beyond Earth has ever been found; there is no evidence that alien life has ever visited our planet.
There is some debate about this, but there's a chance that we have found alien microbial fossils. In 1984, a meteorite that originated on Mars was found in Antarctica. In 1996, odd microscopic formations were found inside that resemble known fossils of bacteria.
The visual resemblance to fossils alone is not enough to prove it is truly evidence of alien life, but it's the most compelling piece of evidence we have now.
List of potentially habitable exoplanets
This is a list of potentially habitable exoplanets. The list is mostly based on estimates of habitability by the Habitable Exoplanets Catalog (HEC), and data from the NASA Exoplanet Archive. The HEC is maintained by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. 
Surface planetary habitability is thought to require orbiting at the right distance from the host star for liquid surface water to be present, in addition to various geophysical and geodynamical aspects, atmospheric density, radiation type and intensity, and the host star's plasma environment. 
10 Silicon-Based Life
Silicon is a molecule whose structure and chemical properties are remarkably similar to the properties of carbon&mdashthe element on which most life on Earth is based. An important part of life as we know it is the ability of carbon to form complex chains of atoms and molecules sufficiently large to contain biological programming such as DNA.
Silicon, also commonly used in computer chips, is the closest that humanity has ever come to designing their own intelligent system. It would have the potential to organically form its own version of DNA under the right circumstances.
Additionally, there are examples on Earth of organisms using silicon in biological structures, specifically in a form of algae known as diatoms. They are responsible for the usage of over six billion metric tons of silicon each year in Earth&rsquos oceans as well as the production of almost 20 percent of the planet&rsquos oxygen. 
As a result, it is likely that silicon might exist as a stage of early life on other planets, converting their atmospheres into oxygen and getting them ready for more advanced life later on.
Super Earth DISCOVERED – Closest ever planet which could house intelligent life FOUND
NASA CGI image of an exoplanet which could potentially support life
When you subscribe we will use the information you provide to send you these newsletters. Sometimes they'll include recommendations for other related newsletters or services we offer. Our Privacy Notice explains more about how we use your data, and your rights. You can unsubscribe at any time.
Hot on the heels of Earth 2 - another planet discovered this summer which has the potential to harbour life - Wolf 1061c is the closest planet outside our solar system which could hold alien life.
Dubbed Earth 3, it is more than four times the mass of Earth. The large planet is still small enough to be rocky with a solid surface, but a year there lasts just 18 days.
It also orbits the Red Dwarf sun within the "Goldilocks zone" meaning its temperature would be just right to hold liquid water so life could potentially develop within its oceans if it has any.
In July NASA held a historic press conference revealing it had founder a "second Earth" using the Kepler telescope.
NASA graphic showing notable exoplanets found by Kepler
Kepler 452b was thought to be rocky and in the Goldilocks zone, but was 1,400 light years away - 100 times further than Wolf 1061c is.
Wolf 1061c is just 14 light years away in the in the constellation of Ophiucus, orbiting the sun called Wolf 1061.
It is one of three planets orbiting the star found by Australian astronomers.
Lead study author Dr Duncan Wright of the University of New South Wales (UNSW), said: "It is a particularly exciting find because all three planets (b, c and d) are of low enough mass to be potentially rocky and have a solid surface.
"The middle planet, Wolf 1061c, sits within the 'Goldilocks' zone where it might be possible for liquid water - and maybe even life - to exist.
Does intelligent life exist on other planets? Technosignatures may hold new clues
Scientists have discovered more than 4,000 planets outside our solar system. In the search for intelligent life, astrophysicists including the University of Rochester's Adam Frank are seeking the physical and chemical signatures that would indicate advanced technology. Credit: NASA/JPL-Caltech
In 1995 a pair of scientists discovered a planet outside our solar system orbiting a solar-type star. Since that finding—which won the scientists a portion of the 2019 Nobel Prize in Physics—researches have discovered more than 4,000 exoplanets, including some Earth-like planets that may have the potential to harbor life.
In order to detect if planets are harboring life, however, scientists must first determine what features indicate that life is (or once was) present.
Over the last decade, astronomers have expended great effort trying to find what traces of simple forms of life—known as "biosignatures"—might exist elsewhere in the universe. But what if an alien planet hosted intelligent life that built a technological civilization? Could there be "technosignatures" that a civilization on another world would create that could be seen from Earth? And, could these technosignatures be even easier to detect than biosignatures?
Adam Frank, a professor of physics and astronomy at the University of Rochester, has received a grant from NASA that will enable him to begin to answer these questions. The grant will fund his study of technosignatures—detectable signs of past or present technology used on other planets. This is the first NASA non-radio technosignature grant ever awarded and represents an exciting new direction for the search for extraterrestrial intelligence (SETI). The grant will allow Frank, along with collaborators Jacob-Haqq Misra from the international nonprofit organization Blue Marble Space, Manasvi Lingam from the Florida Institute of Technology, Avi Loeb from Harvard University, and Jason Wright from Pennsylvania State University, to produce the first entries in an online technosignature library.
"SETI has always faced the challenge of figuring out where to look," Frank says. "Which stars do you point your telescope at and look for signals? Now we know where to look. We have thousands of exoplanets including planets in the habitable zone where life can form. The game has changed."
The nature of the search has changed as well. A civilization, by nature, will need to find a way to produce energy, and, Frank says, "there are only so many forms of energy in the universe. Aliens are not magic."
Although life may take many forms, it will always be based in the same physical and chemical principles that underlie the universe. The same connection holds for building a civilization any technology that an alien civilization uses is going to be based on physics and chemistry. That means researchers can use what they've learned in Earth-bound labs to guide their thinking about what may have happened elsewhere in the universe.
"My hope is that, using this grant, we will quantify new ways to probe signs of alien technological civilizations that are similar or much more advanced to our own," says Loeb, the Frank B. Baird, Jr., Professor of Science at Harvard.
The researchers will begin the project by looking at two possible technosignatures that might indicate technological activity on another planet:
- Solar panels. Stars are one of the most powerful energy generators in the universe. On Earth, we harness energy from our star, the sun, so "using solar energy would be a pretty natural thing for other civilizations to do," Frank says. If a civilization uses a lot of solar panels, the light that is reflected from the planet would have a certain spectral signature—a measurement of the wavelengths of light that are reflected or absorbed—indicating the presence of those solar collectors. The researchers will determine the spectral signatures of large-scale planetary solar energy collection.
- Pollutants. "We have come a long way toward understanding how we might detect life on other worlds from the gases present in those worlds' atmospheres," says Wright, a professor of astronomy and astrophysics at Penn State. On Earth, we are able to detect chemicals in our atmosphere by the light the chemicals absorb. Some examples of these chemicals include methane, oxygen, and artificial gases such as the chloroflourocarbons (CFCs) we once used as refrigerants. Biosignature studies focus on chemicals like methane, which simple life will produce. Frank and his colleagues will catalogue the signatures of chemicals, such as CFCs, that indicate the presence of an industrial civilization.
The information will be gathered in an online library of technosignatures that astrophysicists will be able to use as a comparative tool when gathering data.
"Our job is to say, 'this wavelength band is where you might see certain types of pollutants, this wavelength band is where you would see sunlight reflected off solar panels," Frank says. "This way astronomers observing a distant exoplanet will know where and what to look for if they're searching for technosignatures."
The work is a continuation of Frank's previous research on theoretical astrophysics and SETI, including developing a mathematical model to illustrate how a technologically advanced population and its planet might develop or collapse together classifying hypothetical "exo-civilizations" based on their ability to harness energy and a thought experiment asking if a previous, long-extinct technological civilization on Earth would still be detectable today.
Eight Other Worlds In Our Solar System Might Have Life Beyond Earth
An artist's rendition of a potentially habitable exoplanet orbiting a sun-like star. But we might . [+] not have to find another Earth-like world to find life our own solar system may have all the ingredients we need.
In all the known Universe, to the best that we've examined it, only our home planet, Earth, contains confirmed signs of life. But the raw ingredients required for life appear everywhere, from the interiors of asteroids to interstellar gas clouds to protoplanetary nebulae to the exploded remnants of supernovae. The chemical combinations associated with the building blocks of life, and even complex, organic molecules are found literally everywhere we look in space. But we might not have to venture so far to actually encounter life at all, as eight worlds beyond Earth all offer unique possibilities for the presence of organic, biological activity.
Signatures of organic, life-giving molecules are found all over the cosmos, including in the . [+] largest, nearby star-forming region: the Orion Nebula.
ESA, HEXOS and the HIFI consortium E. Bergin
It’s true that here’s a big gulf between “organic molecules” and what we consider today to be a living organism. Although there are a huge host of interesting possibilities for what’s out there, we’ve so far found nothing else on another world that we’d consider to be “alive,” nor have we found remnants of past life on any worlds. But the Solar System is a great place to start, because it’s so close and accessible! While nothing is for certain, we have a number of intriguing possibilities for where the first signs of life beyond Earth might be found. In order of what we consider most likely to least likely, here are the top eight!
Europa, one of the solar system's largest moons, orbits Jupiter. Beneath its frozen, icy surface, a . [+] liquid water of ocean is heated by tidal forces from Jupiter.
NASA, JPL-Caltech, SETI Institute, Cynthia Phillips, Marty Valenti
1.) Europa. Jupiter’s second of its four large moons, Europa might at first seem like it’s too far from the Sun to be a good candidate for life. But Europa has two special things going for it: a ton of water — more water than is present on all of Earth — and some internal heating due to the tidal forces of Jupiter. Beneath a surface of ice, Europa has an enormous ocean of liquid water, and the heating of its insides due to Jupiter’s gravity may create a situation very analogous to the life-giving hydrothermal vents on the Earth’s ocean floor. It’s not likely to be life like we see on the surface of Earth, but life that can survive, reproduce and evolve is life any way you slice it.
One of the most intriguing -- and least resource-intensive -- ideas for searching for life in . [+] Enceladus' ocean is to fly a probe through the geyser-like eruption, collecting samples and analyzing them for organics.
NASA / Cassini-Huygens mission / Imaging Science Subsystem
2.) Enceladus. Saturn’s icy moon is smaller and has far less water than Europa, but it announces its liquid ocean (beneath a surface of solid ice) uniquely: by spewing 300-mile plumes of water into space! These geysers let us know for certain that there’s liquid water, and in tandem with the other elements and molecules necessary for life, such as methane, ammonia and carbon dioxide, there just might be life beneath the oceans of this world, too. Europa has more heat, more water and hence — we think — a greater chance, but don’t count Enceladus out, since it has a thinner ice surface and erupts far more spectacularly, meaning that we could find life with an orbiting mission, rather than having to drill down beneath the surface!
The flow of a dried-up riverbed is an unmistakable signature of a water-rich past on Mars.
3.) Mars. The red planet was once clearly very, very Earth-like. For perhaps the first billion years of the Solar System, water flowed freely across the martian surface, carving rivers, accumulating in lakes and oceans, and leaving remnant evidence that shows us, today, where they were once located. Features associated with a watery past, like hematite spherules (often associated with life on Earth), are common. In addition, the Curiosity rover has found an active, underground and variable source of methane, a possible signature of life today. And now that we know liquid water appears on the martian surface, albeit in a very salty environment, the door is definitely open. Is there life? Was there life at one point, but no longer? Mars remains a tantalizing possibility.
The surface of Titan, beneath the clouds, was found to contain methane lakes, rivers and waterfalls. . [+] Could it also be home to some type of life?
ESA, NASA, JPL, University of Arizona panorama by Rene Pascal
4.) Titan. Enceladus might offer the greatest possibility for Earth-like life in the Saturnian system, but perhaps life takes on a different form from the water-based biology here on Earth? With a thicker atmosphere than our own planet, the second-largest moon in our Solar System, Titan, was found to have liquid methane on its surface: oceans, rivers and even waterfalls! Could life make use of methane on another world the same way it makes use of water on Earth? If the answer to that is yes, there just might be living organisms on Titan today.
The surface of Venus, from the only spacecraft to ever successfully land and transmit data from that . [+] world.
5.) Venus. Venus is hell, literally. At a constant surface temperature of some 900 degrees Fahrenheit, no human-made lander has ever survived more than a couple of hours while touched down on our nearest neighboring planet. But the reason Venus is so hot is because of it’s thick, carbon-dioxide rich atmosphere laden with heat-trapping clouds of sulphuric acid. This renders the surface of Venus thoroughly inhospitable, but the surface isn’t the only place to look for life. In fact, speculation is rampant that perhaps something interesting is happening some 60 miles up! Above the cloud-tops of Venus, the environment is surprisingly Earth-like: similar temperatures, pressures, and less corrosive material. It’s conceivable that with its own unique chemical history, that environment is filled with carbon-based airborne life, something that a mission to Venus' upper atmosphere could easily sniff out.
The Voyager 2 spacecraft took this color photo of Neptune's moon Triton on Aug. 24 1989, at a range . [+] of 330,000 miles. The image was made from pictures taken through the green, violet and ultraviolet filters.
6.) Triton. You might not have heard much of Neptune’s largest moon, but it’s remarkable and unique among all the worlds of the solar system. It has “black smoker” volcanoes, it rotates and revolves the wrong way, and it originated from the Kuiper belt. Larger and more massive than both Pluto and Eris, it was once the king of all Kuiper belt objects, and now, in orbit around our Solar System’s final planet, we recognize that it’s covered in many life-giving materials, including nitrogen, oxygen, frozen water and methane ices. Could some form of primitive life exist at these energy interfaces? It's certainly worth a look!
This global map shows the surface of Ceres in enhanced color, encompassing infrared wavelengths . [+] beyond human visual range.
7.) Ceres. It might sound crazy to think of the possibility that life might exist on an asteroid. Yet when asteroids fall to Earth, we find not just the 20 amino acids essential to life, but nearly 100 others: the building blocks are all there! Could the largest asteroid of them all, the one with those bizarre, salt-deposit “white spots” on the bottom of its brightest craters, actually house some form of life? Although the answer is “probably not,” it’s conceivable that it was actually collisions with asteroids and Kuiper belt objects that brought either the raw ingredients for life or pre-existing, primitive life to Earth. What we consider, today, to be active biology, might have begun before Earth ever formed. If so, the signatures might be embedded within a world like Ceres, which is the best candidate for life in the asteroid belt. We just have to look to find out. And finally.
Pluto's atmosphere, as imaged by New Horizons when it flew into the distant world's eclipse shadow.
NASA / JHUAPL / New Horizons / LORRI
8.) Pluto. Who would’ve expected that history’s outermost world — at a temperature just 100 degrees Fahrenheit above absolute zero — would be a candidate for life? And yet, Pluto has an atmosphere, it has remarkable, changing surface features, it has the same ices that Triton has, and objects just like it may be responsible for bringing much of what looks like Earth’s atmosphere and oceans to our planet. Could it have brought life as well? New Horizons will bring us hints, but to find out for certain, we'll need a landing mission.
The "holy cow" mosaic of the Mars Phoenix mission, with revealed water-ice clearly visible . [+] underneath the lander's legs. In order to learn the maximum amount possible about the presence or absence of life on a world, you absolutely must touch down and look, explicitly, for the surefire signatures.
NASA / JPL / University of Arizona / Max Planck Institute / Spaceflight / Marco Di Lorenzo, Kenneth Kremer / Phoenix Lander
We always think of ourselves as alone in both the solar system and in the greater Universe, and yet that may be more a function of us looking for things exactly like us than of us actually being alone. If we go and investigate, we might not only find life in unexpected, thought-to-be-inhospitable places, we might wind up finding life that looks very little like the life we currently understand. Our logic, our intuition and our inklings can only get us so far. If we want to know, we have to go and look. Every time we've done exactly that, the Universe has had a wonderful way of surprising us.
Top 10 Proof Of Alien Life On Other Planets
Is there any form of life in various other parts of the Universe? This is certainly one of the popular questions within the mind of the astronauts, scientists and even common people. To give an answer to this question, below are discussed about top 10 proof of alien life on other planets.
(1) Image of a workman on Mars
Pictures captured by Mars Curiosity Rover certainly prove that there is alien life on Mars. The image shows the shadow of a human like figure who was working on a space craft. Even though the unidentified being was wearing a suit commonly worn by the human astronauts but it was certainly without a helmet. Since humans cannot leave in the toxic environment of Mars, it certainly proves that the unidentified being was an alien.
(2) Existence of Aliens on Europa, Jupiter’s beautiful moon
According to sources, this is also one of the prime locations of the aliens. For more than 20 years, astrobiologists have been researching to gather vital information about existence of life on Europa, Jupiter’s beautiful moon. Researchers claim that one of the major reasons behind existence of life in this place is due to the tidal energy exerted on Europa by the powerful gravitational force of Jupiter. Christopher McKay, senior space scientists in Astrobiology Division at NASA Ames Research Center and Space Science claims that Europa is the best place for alien existence.
(3) Alien Autopsy Photos
The alien autopsy photos that have been captured by Area 51 certainly prove that there is existence of alien life on other planets. Later on, the autopsy photos became major evidence after Tom Carey, a UFO expert and Kodak verified that images were real and no Photoshop software has been used to create them.
(4) Fish shaped alien peeking out of the cave on Mars
This is a terrific incident that has been captured by the NASA’s Curiosity Rover. Scott C Waring, one of the renowned UFO researcher claims that a fish shaped alien was continuously peeking through the cave on Mars. He also alleged that the rover has also been able to capture a video of a crashed drone besides the cave. This certainly proves that there is existence of alien life on Mars.
(5) Existence of primitive alien on Titan
Research conducted by various renowned scientists has highlighted that there is evidence of life on Titan, the biggest moon of planet Saturn. They have also been able to discover that the primitive aliens are breathing on the atmosphere of Titan and thereby there is a gradual decrease in the level of hydrogen from the surface of the moon.
(6) Alien life on Pluto
According to photos released by NASA on October 2015, there is evidence of alien existence on Pluto. UFO highlights that the images captured on Pluto proves that a giant alien ship has been parked on the Blue Ridge Mountain of this planet,
(7) Astronauts on Apollo 11 detected a rocket flying alongside
The astronauts on Apollo 11 sent a message to the control room to get an idea whether S-4B, the detached part of the rocket was still nearby. This unusual question was asked by them after they were able to detect that something was flying along side of their rocket. Later, they were able to determine that it was a space craft of some unidentified visitor.
(8) Presence of alien on Enceladus
According to various researches conducted by NASA, it has been found that there is a huge body of water beneath the Enceladus, sixth largest moon of Saturn. Scientists further highlight that if there is an existence of water beneath this moon then there must be existence of aliens in this place.
(9) Mysterious signals received during the SETI project
In the year 2003, when astronauts were in search of extraterrestrial life using massive telescope received a high frequency radio signals that disappeared suddenly, except one that became stronger. This signal is evidence that there is alien life in other planet.
(10) Evidence of life on Venus
According to a research conducted by famous Russian astronaut, it has been found that there is existence of life in the planet Venus. Photographs captured on the space highlight that there is existence of several forms life on Venus.
Have We Found Alien Life?
This feature was originally published in the February 2015 issue of Popular Science.
Kenneth Nealson is looking awfully sane for a man who’s basically just told me that he has a colony of aliens incubating in his laboratory.
We’re huddled in his modest office at the University of Southern California (USC), on the fifth floor of Stauffer Hall. Nealson is wearing a rumpled short-sleeve shirt, a pair of old suede loafers, white socks—your standard relaxed academic attire—and leaning back comfortably in his chair. An encouraging collection of academic awards hangs on one wall. Propped behind him is a well-worn guitar, which he sometimes breaks out to accompany his wife’s singing. And across the hall is the explanation for his quiet confidence: beakers and bottles full of bacteria that are busily breaking the long-accepted rules of biology.
Life, Nealson is explaining, all comes down to energy. From the mightiest blue whale to the most humble microbe, every organism depends on moving and manipulating electrons it’s the fuel that living matter uses to survive, grow, and reproduce. The bacteria at USC depend on energy, too, but they obtain it in a fundamentally different fashion. They don’t breathe in the sense that you and I do. In the most extreme cases, they don’t consume any conventional food, either. Instead, they power themselves in the most elemental way: by eating and breathing electricity. Nealson gestures at his lab. That’s what they are doing right there, right now.
“All the textbooks say it shouldn’t be possible,” he says, “but by golly, those things just keep growing on the electrode, and there’s no other source of energy there.” Growing on the electrode. It sounds incredible. Nealson pivots on his chair to face me and gives a mischievous grin. “It is kind of like science fiction,” he says. To a biologist, finding life that chugs along without a molecular energy source such as carbohydrates is about as unlikely as seeing passengers flying through the air without an airplane.
That discovery comes with some sizable implications. On a practical level, electric bacteria could be harnessed to create biological fuel cells or to clean up human waste. Nealson tells me that one of his former students just got a grant to build a bacteria-powered sewage system. But more to the point, such microbes appear to comprise a vast, largely unexplored realm of life on this planet. There’s a chance they are an important part of the biodiversity on planets beyond ours too.
Nealson never utters the word “aliens,” but it hangs heavily over the conversation. His bacteria are unlike anything we’ve ever encountered, and they are forcing us to rethink life as we know it.
Like any good alien story, this one begins with an abduction—though one of a decidedly scientific variety. The abductee in this case was not a person but a mineral. Nealson settles in to tell the tale.
In 1982, he was a professor at the Scripps Institution of Oceanography when he heard about strange goings-on in Oneida Lake in upstate New York. Each spring, snowmelt washes manganese out of the surrounding mountains and into the lake. Winds then whip up the waters, allowing the dissolved metal to combine efficiently with oxygen to form solid manganese oxide, which sinks to the lake bed. The trouble was, scientists didn’t find nearly as much as they anticipated. Something was making the manganese oxide vanish, at more than 1,000 times the geologically expected rate, and nobody could figure out what.
“If rates were really that fast, I knew it had to be due to biology,” Nealson says. He suspected bacteria in the lake were getting rid of the manganese oxide almost as quickly as it formed. That theory made perfect sense, but it ran counter to the textbook wisdom: that microbes cannot break down a raw piece of metal any more than you or I can. The mystery kept itching at him. In 1985, Nealson relocated to the University of Wisconsin–Milwaukee, and began research at Oneida Lake to prove his hunch correct.
After a two-year search, Nealson succeeded in identifying the manganese thief: Shewanella, a bacterium that functioned unlike any he had ever known. “As soon as I saw what Shewanella could do, I just went wacky,” Nealson says. “I called all my students into the lab and I said, ‘This is a very, very important organism to understand. Nobody’s going to believe it. It’s going to take us 10 or 15 years to convince the world it’s true.’?”
For most living, air-breathing creatures, Nealson says, “The glucose that we eat supplies the electrons, the oxygen we breathe receives the electrons, and that electron flow is what runs our bodies.” That’s basic metabolism. The challenge for every organism is finding both sources of electrons and places to discard them in order to complete the circuit. Shewanella consumes electrons from carbohydrates, but it sheds them in an unusual way: “It swims up to the metal oxide and respires it.” Nealson says. “We call this ‘breathing rocks.’?” Here is where the scientific heresies begin.
Shewanella‘s outer membrane is full of tiny chemical wires, enabled by specialized proteins, that let it move electricity out of the cell. The wires make direct contact with the manganese oxide, which is how it can deposit electrons and “breathe” a solid substance. Furthermore, Nealson realized that the bacterium doesn’t even care whether the substance on the outside of its membrane is manganese oxide or something else entirely, so long as it will complete the electric circuit.
While Nealson and his team were gathering proof that Shewanella is as extraordinary as it seemed, another microbiologist made a similar discovery. Derek Lovley, then a project chief at the U.S. Geological Survey, found an electron-moving bacterium, Geobacter, living on the bottom of the Potomac River. “Geobacter‘s proteins have a completely different evolutionary origin, but they solve the problem the same way,” Nealson says. Finding two unrelated microbes with an affinity for raw electricity provided reassuring evidence that Shewanella wasn’t some one-off weirdo.
At this point, Nealson realized the microbial landscape of the planet might be different than anyone had thought. He also realized he had probably only just begun to explore what electric bacteria are capable of.
“Nobody’s going to believe it. It’s going to take us 10 or 15 years to convince the world it’s true.”
Annette Rowe, a postdoc researcher in Nealson’s group, is currently speeding through life’s outer limits in the lab across the hall from where I was talking with Nealson. There are fish tanks, test tubes, wires, incubators, and anaerobic chambers with push-through working gloves that look like old set pieces from CSI. I pass a large tank of slow-stirring liquid, with a family of Shewanella growing inside. (“Yeah, too bad you can’t see them,” Rowe says apologetically.) Motivational photos of Nealson gaze down from tall shelving racks. Sample captions: “I AM WATCHING YOU” and “GET YOUR ASS TO WORK.”
The place looks vaguely like an aquarium for microbes, and in fact that’s pretty much what it is. Just as Nealson found Shewanella in Oneida Lake, Rowe and her collaborators have been scouting local marine settings for other electric bacteria, the stranger the better, then cultivating them and trying to figure out what makes them tick.
“We’ve been working in Catalina Harbor. They have a really nice study system out there,” she says. Rowe has the slightly weary look of a graduate student who pulls a lot of late hours, but she lights up when she talks about getting into the field. “Basically, we pull up sediment and sieve it to get rid of invertebrates, and get a nice well-mixed system at the same time. We set up 10-gallon aquariums full of this sediment and bury electrodes in it. And then we look for signs of bacterial colonization.”
The electrode is the key to attracting the type of bacteria Rowe is looking for: not the kind that dumps electrons onto minerals, but the kind that scavenges electrons from them. Not breathers, but eaters. To those bacteria, a cathode looks like one enormous, electrically charged dinner table. Rowe adjusts the electric potential to mimic compounds the organisms might normally draw their energy from, and they swim right up.
As Rowe began sorting through her tanks of sedimentary muck, she was struck by the sheer diversity of bacteria she’d collected. “I’ve isolated a whole slew of electrode-oxidizing bugs,” she says—roughly a thousand strains in total. So far, she’s identified 30 of them, all previously unknown.
One important lesson that has emerged from Rowe’s work is that bacteria have a wide variety of mechanisms for moving electrons around. That finding suggests the ability evolved multiple times. Even more surprising, some of the bacteria, including Shewanella, can swing both ways. “A lot of organisms that can put electrons onto an electrode can also do the opposite and take electrons from one”—though not at the same time—Rowe says. That ability to reverse course surprises me, and Rowe, too. “I’d think it would be really hard on the organisms. You’re basically stealing energy from them. But they do okay.”
Another discovery is even more astonishing. Six of Rowe’s new bacterial strains can live on electrons alone. “It’s a crazy phenomenon,” she says, one that is well beyond anything Nealson had discovered up to now. “I’ve kept some of these bugs for over a month with no addition of carbon,” she says. They must be subsisting solely on electricity from the electrode, because there is nothing else.
These microbes are the ones that had Nealson so worked up in our earlier conversation. They are not just new to science they require an entirely new method of collection and culture. The vast majority of Rowe’s strains must be grown on a cathode, not in a petri dish. And they indicate an immense and largely alien ecosystem here on Earth. The National Science Foundation calls it the “dark energy biosphere” and is funding Rowe to learn more about this parallel microbial universe.
These microbes indicate an immense and largely alien ecosystem here on Earth.
To Nealson, his protégé’s breakthrough both validates and stomps all over his own revelations about how life works: “I’ve been doing microbiology for 45 years,” he says. “It’s just wild to have your whole view change so drastically.”
Caught On Camera
As staggering as Rowe’s findings are, there is a certain level of intellectual remoteness to all that talk about electrons and energy levels. No matter how much I stare into the flask, I still keep wishing I could see what the bacteria are doing with my own eyes. That frustration dissipates when I stop in on Moh El-Naggar, who works a couple buildings over on the USC campus. He has actual videos of the microbes in action, unspooling wires and setting up microscopic electrical grids.
El-Naggar’s bacterial video project began as an effort to disprove a theory. Experiments Nealson had done with Shewanella showed that the bacteria can make contact with a metallic surface to deposit electrons. Other studies had revealed that bacteria sometimes produce hairlike appendages of unknown function. Some researchers dismissed those growths as unimportant, but a few wondered whether the hairs were actually “nanowires” created by the bacteria to move electrons.
Video: Electric nanowires stretch from the outer membranes of Shewanella oneidensis bacteria. Credit: El-Naggar et al./PNAS 2014, Courtesy USC
To El-Naggar, that reasoning seemed too tidy: “I kind of went into it thinking, it can’t really work that way, right? I’m going to do the measurements that show it doesn’t.” So El-Naggar did what any good home handyman would. He clipped a couple leads onto the wires to see if they conduct electricity. They do. Then he checked to see if the circuit is live, with current flowing across the wires. It is. Finally, he monitored the wires as they form, recording the cells lighting up with activity once they complete a circuit.
Afterward, he had a series of mind-boggling movies in which you can watch Shewanella reach out to an electrode in search of a place to deposit electrons. Sometimes the bacteria will link up with one another, possibly fobbing off electrons on cells that are able to accept them. El-Naggar describes the shock that runs through the room when he shows his videos at conferences: “You’re sitting there in the dark, you start the movie, and then you hear, ‘Ahh! Cool!’?”
Nanowires may be related to yet another widespread but newly discovered bacterial talent, the ability to connect into sausage-link cables thousands of cells long. As yet there is no indication whether Rowe’s electric bacteria form these kinds of cables (the research is far too new), but studies at Aarhus University in Denmark indicate that such cables do support a flow of electrons. El-Naggar speculates that the cables are like drinking straws, allowing bacteria buried deep in sediment to breathe from the top of the pile by pushing electrons up through the tube, from one cell to the next.
Just a few years ago, nobody imagined that any bacteria were capable of such behaviors. Now El-Naggar suspects that nanowires and cables are used widely by bacteria, and not just among the most extreme electron-eaters. He is collaborating with colleagues in the dental school at USC to examine evidence of nanowires in the bacterial films that form in people’s mouths cell-to-cell electrical linkages might in fact be a general characteristic of biofilms, bacterial collectives, both benign and pathogenic, that take up residence on a surface.
Shelley Minteer, an electrochemist at the University of Utah, has probed even deeper into cell biology. She discovered that mitochondria—the power-generating units inside the cells of all complex cellular organisms, including humans—can interact electrically with surfaces outside themselves. That fits with a well-accepted theory that mitochondria evolved as free-living bacteria that later merged with other cells, forming a permanent partnership. Even after a billion years, mitochondria may retain some of the capabilities they had in their days of independence. It is possible, then, that we all have a smidgen of electric alien behavior locked away inside us.
It is possible we all have a smidgen of electric alien behavior locked away inside us.
My first trip from Nealson’s office took me across the hall. My last trip takes me to Mars. Not such a big leap, actually: Nealson has never made a clean philosophical distinction between the search for exotic life on Earth and the search for life on other planets. For several years he worked at NASA’s Jet Propulsion Lab (JPL), where he set up the astrobiology group. Now the ideas he developed there will get a formal test aboard the upcoming Mars2020 rover.
In some ways, getting to Mars is a cakewalk compared to the challenge of knowing what to search for once you arrive. The Viking missions in the 1970s landed just fine but got tripped up by things that smelled like life. The scientists studying the infamous Mars meteorite in the 1990s may have been led astray by things that looked like life. And the fancy new Curiosity rover has found intriguing whiffs of methane, but their connection to biology is utterly unknown. That’s what Nealson’s team grappled with at JPL. “Could you really figure out what the universal properties of any life must be? It’s very hard to solve this problem, because we can’t get away from our own biases,” he says.
SHERLOC is part of the answer. It is one of seven science instruments aboard Mars2020. One of Nealson’s former JPL employees, Rohit Bhartia, was a lead designer, and the instrument is heavily informed by the lessons of metal-breathing bacteria. Shewenella expanded scientists’ understanding of metabolism, and so SHERLOC will be looking for a wider spectrum of possible biosignatures. It will zap targets with ultraviolet rays and look for visual effects that indicate certain organic compounds and minerals.
Although SHERLOC will not be searching for life per se—only for the trail it leaves behind—electric bacteria suggest new ways to find active alien biology as well. All of the electric adaptations are responses to extreme environments. Scrounging for electrons and sprouting nanowires are strategies for surviving when there is not enough food to do much growing and competing—just enough to help an organism hunker down and keep the flame of life lit. Such conditions are common in deep ocean sediments and far underground. If life exists on Mars and other worlds (Europa? Titan?), there’s a good chance that it, too, is huddled in resource-constrained settings far beneath the surface.
While NASA gears up for Mars2020, Rowe and others in the USC group are bio-prospecting for more electric bacteria here on Earth, relocating their operation from the shallow waters around Catalina Island to deep boreholes in the Mojave desert and mines in South Dakota. These sites could not only expose more of Earth’s hidden biodiversity they could also help guide thinking about possible alien biologies. “When we go to other planets, we look for life on the surface, but really there’s so much energy in the subsurface,” Nealson says. “I’ll be astounded if this extracellular electron transport isn’t the rule there.”
In the process of poking electrodes into different environments and rounding up electric microbes, Nealson’s team has noted a distinctive pattern: Stick a spike in the ground pretty much anywhere on Earth, and you can measure the electric potential steadily dropping off the deeper you go. That’s because microbes at each depth are chasing after whatever electrons are available. The most energetic organisms, using the most energetic reactions, live up top, where resources are the most abundant. The farther you go into the regions of scarcity, the more life has to grab at any energy it can get.
That electric gradient sure sounds like another good candidate for a universal signifier of life. “If there isn’t life, there shouldn’t be gradients,” Nealson says. So instead of running complicated chemical experiments that might miss some unfamiliar type of biological activity, he muses, why not stick a giant probe in Mars and replicate Rowe’s microbe hunting expeditions in Catalina? He envisions a whole flock of javelin-like probes that drop from an orbiter and penetrate the ground all around the planet. Each one would have a little transponder to send data up to the science satellites already circling the Red Planet. The probes would look for electrical gradients, flagging possible locations of biological activity for closer study. NASA and Russia have attempted simpler Mars penetrators, though both missions failed. Now the nonprofit Explore Mars is trying to raise funds for an “ExoLance” to seek subsurface life there.
“When we go to other planets, I’ll be astounded if this extracellular electron transport isn’t the rule there.”
Nealson is on a roll, so I goad him on: Could you do the same thing on Europa? He slows down for only a beat. “Europa is tough, because it’s all ice. . . . You would imagine that you would put something on the surface with a solar panel or a radioactive generator and just melt your way down in with the probe. You could radiation-harden just the little thing above the electronics.”
If they find no signs of electric biology, the probes could still measure geochemistry beneath the surface, which is valuable in and of itself. And if they do find it, popping champagne corks would be premature: You’d want to see if it is dynamic, changing with daylight or temperatures, for instance. That kind of additional signal would be strong circumstantial evidence of life. It still wouldn’t be the definitive discovery of ET, but it would tell you exactly where to go back—this time with a microscope.
The Shadow Biosphere
As we are talking, I find myself in the middle of a very different kind of conversation about the nature of life. At one point, Nealson pauses to inform other members of the lab that a close friend and colleague, Katrina Edwards, died over the weekend. Then he interrupts again, explaining that he has to drop off his retirement papers with the dean, easing himself into a four-year exit. When Nealson returns, he indulges in a little reflection. His only real regret, he tells me, is that he won’t have enough time to study Rowe’s all-electric bacteria himself: “It really pisses me off that I discovered this when I was 70 years old, because it’s important.”
Electrically active bacteria could have many practical benefits that researchers are now beginning to explore. They turn out to have an incredible talent for sewage treatment, for example. Stick an electrical anode in human waste and it attracts communities of bacteria that eat feces and breathe electrons. Hook them up to a fuel cell and you have a self-powered wastewater treatment system that produces significantly less sludge. One of Nealson’s former students, Orianna Bretschger, set up a test system at the J. Craig Venter Institute in San Diego, where it’s been running for five years with practically no maintenance. “My personal goal is developing these systems to a point where we could fly them into villages in the third world,” says Nealson, who still collaborates with Bretschger. “People would bring their sewage to the treatment plant and get clean water, and you wouldn’t need any outside power.”
Daniel Bond at the University of Minnesota is exploring the potential for electric bacteria to generate power and synthesize novel materials. The defense department is reportedly interested in underwater sensors driven by bacteria. El-Naggar suspects that electrical interactions between bacterial and human cells may have important, almost entirely unexplored health implications. After all, the sewage experiments indicate there are electrically active bacteria in the gut. He wonders aloud: Do they communicate with human cells as part of the body’s internal ecosystem?
All of these possible applications derive from the sheer unfamiliarity—the utter alien-ness—of Shewanella and its even stranger cousins. They are alien not just in what they do but in how they do it. Their Earth seems to be a world built on cooperation and sharing, a far cry from the more familiar world of cutthroat Darwinian competition. “Unless I miss my bet, that’s what we’re going to see when we get to the subsurface: little pockets of life with a socialist community, all working there together. But I won’t tell that to my Republican father because he won’t like it,” Nealson says.
I think of electric socialism as an exotic idea, but Nealson quickly convinces me otherwise. It may be the normal way things work in environments where resources are scarce and predatory competition is not an advantage. It may have been life’s reality through much of its history on this planet. (“I always thought that bacteria never learned to grow fast until predators evolved,” he says. “What’s the rush? You know, bacteria don’t eat other bacteria.”) In fact, it may suit more of today’s life than most scientists realize, since so much of Earth’s microbial ecosystem is still out of sight. By some estimates, 99.9 percent of all species cannot be cultured in a petri dish. Slow, collaborative living may be life’s way on many other worlds as well.
That’s a lot of maybes, so I put this to Nealson: Does he really believe in a shadow biosphere, built around electron sharing and microscopic collectivism? “Before I kick the bucket, I hope that is proven to be true,” he says. Then he corrects himself, like a proper open-minded scientist. “I mean, I don’t. It’s okay with me if it’s not true, but I’ll be really surprised. It makes so much sense, and life usually makes sense.”
How To Find Alien Life
1. Test For Metabolic Activity
The first serious attempt to find alien life took place in 1976, when the twin Viking probes sought out organisms by mixing Martian soil with nutrients and radioactive carbon. The results were negative (you probably knew that), but clouded by the complex soil chemistry.
2. Follow The Water
NASA’s current Mars research, led by the $2.5 billion Curiosity rover, focuses on learning whether the planet once had a warm, wet environment. Studies of Gale Crater look encouraging unfortunately, these efforts show only that Mars could have sustained life, not that it actually did.
3. Scan For Organics
Taking lessons from Viking and Curiosity, NASA’s upcoming Mars2020 rover will include two instruments that scan the environment for signs of organic compounds. This technique can cover a lot of ground, and does not make specific assumptions about the metabolism of Mars life.
4. Look For Chemical Organization
Another approach would be to seek out chemical patterns suggestive of biological activity. For example, DNA is full of repeating molecular motifs. More subtly, there are almost no natural nitrogen-bearing minerals, so an array of nitrogen compounds would raise a red flag.
5. Measure Electric Potential
All life manipulates electrical energy. If the electric potential in the ground drops steadily with depth (as happens on Earth), that could indicate successive populations of microbes are pulling electrons from the environment. It would be a low-key First Contact, but revolutionary all the same.
Some of the best evidence for life in space lives right here on Earth: It’s weird, adaptable, and far hardier than we ever thought. —Alissa Zhu
TardigradeIn an experiment in 2007, tardigrades became the first multicellular creatures to be exposed to the vacuum of space and live. They can withstand temperatures barely above absolute zero, pressure exceeding that in the deepest ocean trenches, and deadly levels of radiation. They have no skeletal or circulatory systems, and no one knows how long they can survive. Tardigrades delay death by moving in and out of cryptobiosis—essentially, suspended animation.
Deep-Sea ShrimpAlong deep-sea hydrothermal vents in the Caribbean, in an ecosystem totally devoid of sunlight, a species of shrimp called Rimicaris hybisae thrives by coexisting with chemosynthetic bacteria. “That makes them analogous with organisms potentially living in Europa,” says Max Coleman, an astrobiologist studying them for NASA. The bacteria colonize the crustaceans’ specially adapted gill covers and use hydrogen sulfide to produce organic matter for the shrimp to eat.
BlobfishThe blobfish is best known for being voted “the world’s ugliest animal” by the Ugly Animal Preservation Society, but its gelatinous form is notable for another reason: It enables the fish to inhabit waters thousands of feet deep off the coast of Australia, where pressure is several dozen times higher than at sea level. Because a swim bladder would be ineffective at such depths, the blobfish uses its whole jelly-like body for buoyancy.
Lyme Disease BacteriaThe bacterium that causes Lyme Disease is the only known organism that doesn’t need iron for its basic life chemistry. Instead, Borrelia burgdorferi uses manganese and other minerals. Johns Hopkins University microbiologist Valeria Culotta says that makes our defense against the infection virtually futile: “When the immune system tries to starve it of iron, it says, ‘I don’t care. You can make yourself as anemic as you want but it won’t affect me.'”
The James Webb Space Telescope, launching in 2021, could get the first glimpses: the mix of gases in the atmospheres of Earth-sized exoplanets. Webb, or a similar spacecraft in the future, could pick up signs of an atmosphere like our own &ndash oxygen, carbon dioxide, methane. A strong indication of possible life. Future telescopes might even pick up signs of photosynthesis &ndash the transformation of light into chemical energy by plants &ndash or even gases or molecules suggesting the presence of animal life. Intelligent, technological life might create atmospheric pollution, as it does on our planet, also detectable from afar. Of course, the best we might be able to manage is an estimate of probability. Still, an exoplanet with, say, a 95 percent probability of life would be a game changer of historic proportions.
Life might turn up in our own neighborhood: beneath the Martian surface, perhaps, or in the dark, subsurface oceans of Jupiter's moon, Europa. Or maybe the dream of the ages will come true, and we'll eavesdrop on the communications of extraterrestrial civilizations. We might even capture evidence of "technosignatures," or traces of technology (think smog). Barring these strokes of luck, however, the job will be much harder. Light will be the key &ndash light from the atmospheres of exoplanets, split up into a rainbow spectrum that we can read like a bar code. This method, called transit spectroscopy, would provide a menu of gases and chemicals in the skies of these worlds, including those linked to life.
Life probably exists beyond Earth. So how do we find it?
In her office on the 17th floor of MIT’s Building 54, Sara Seager is about as close to space as you can get in Cambridge, Massachusetts. From her window, she can see across the Charles River to downtown Boston in one direction and past Fenway Park in the other. Inside, her view extends to the Milky Way and beyond.
Seager, 47, is an astrophysicist. Her specialty is exoplanets, namely all the planets in the universe except the ones you already know about revolving around our sun. On a blackboard, she has sketched an equation she thought up to estimate the chances of detecting life on such a planet. Beneath another blackboard filled with more equations is a clutter of memorabilia, including a vial containing some glossy black shards.
“It’s a rock that we melted.”
Seager speaks in brisk, uninflected phrases, and she has penetrating hazel eyes that hold on to whomever she is talking to. She explains that there are planets known as hot super-Earths whizzing about so close to their stars that a year lasts less than a day. “These planets are so hot, they probably have giant lava lakes,” she says. Hence, the melted rock.
“We wanted to test the brightness of lava.”
When Seager entered graduate school in the mid-1990s, we didn’t know about planets that circle their stars in hours or others that take almost a million years. We didn’t know about planets that revolve around two stars, or rogue planets that don’t orbit any star but just wander about in space. In fact, we didn’t know for sure that any planets at all existed beyond our solar system, and a lot of the assumptions we made about planet-ness have turned out to be wrong. The very first exoplanet found—51 Pegasi b, discovered in 1995—was itself a surprise: A giant planet crammed up against its star, winging around it in just four days.
“51 Peg should have let everyone know it was going to be a crazy ride,” Seager says. “That planet shouldn’t be there.”
Today we have confirmed about 4,000 exoplanets. The majority were discovered by the Kepler space telescope, launched in 2009. Kepler’s mission was to see how many planets it could find orbiting some 150,000 stars in one tiny patch of sky—about as much as you can cover with your hand with your arm outstretched. But its ultimate purpose was to resolve a much more freighted question: Are places where life might evolve common in the universe or vanishingly rare, leaving us effectively without hope of ever knowing whether another living world exists?
Kepler’s answer was unequivocal. There are more planets than there are stars, and at least a quarter are Earth-size planets in their star’s so-called habitable zone, where conditions are neither too hot nor too cold for life. With a minimum of 100 billion stars in the Milky Way, that means there are at least 25 billion places where life could conceivably take hold in our galaxy alone—and our galaxy is one among trillions.
It’s no wonder that Kepler, which ran out of fuel last October, is regarded almost with reverence by astronomers. (“Kepler was the greatest step forward in the Copernican revolution since Copernicus,” University of California, Berkeley astrophysicist Andrew Siemion told me.) It’s changed the way we approach one of the great mysteries of existence. The question is no longer, is there life beyond Earth? It’s a pretty sure bet there is. The question now is, how do we find it?
The revelation that the galaxy is teeming with planets has reenergized the search for life. A surge in private funding has created a much more nimble, risk-friendly research agenda. NASA too is intensifying its efforts in astrobiology. Most of the research is focused on finding signs of any sort of life on other worlds. But the prospect of new targets, new money, and ever increasing computational power has also galvanized the decades-long search for intelligent aliens.
To Seager, a MacArthur “genius award” winner, participating on the Kepler team was one more step toward a lifelong goal: to find an Earth-like planet orbiting a sunlike star. Her current focus is the Transiting Exoplanet Survey Satellite (TESS), an MIT-led NASA space telescope launched last year. Like Kepler, TESS looks for a slight dimming in the luminosity of a star when a planet passes—transits—in front of it. TESS is scanning nearly the whole sky, with the goal of identifying about 50 exoplanets with rocky surfaces like Earth’s that could be investigated by more powerful telescopes coming on line, beginning with the James Webb Space Telescope, which NASA hopes to launch in 2021.
On her “vision table,” which runs along one wall of her office, Seager has collected some objects that express “where I am now and where I’m going, so I can remind myself why I’m working so hard.” Among them are some polished stone orbs representing a red dwarf star and its covey of planets, and a model of ASTERIA, a low-cost planet-finding satellite she developed.
“I haven’t gotten around to putting this up,” Seager says, unrolling a poster that’s a fitting expression of where her career began. It’s a chart showing the spectral signatures of the elements, like colored bar codes. Every chemical compound absorbs a unique set of wavelengths of light. (We see leaves as green, for instance, because chlorophyll is a light-hungry molecule that absorbs red and blue, so the only light reflected is green.) While still in her 20s, Seager came up with the idea that compounds in a transiting planet’s upper atmosphere might leave their spectral fingerprints in starlight passing through. Theoretically, if there are gases in a planet’s atmosphere from living creatures, we could see the evidence in the light that reaches us.
“It’s going to be really hard,” she tells me. “Think of a rocky planet’s atmosphere as the skin of an onion, and the whole thing is in front of, like, an IMAX screen.”
There’s an outside chance a rocky planet orbits a star close enough for the Webb telescope to capture sufficient light to investigate it for signs of life. But most scientists, including Seager, think we’ll need to wait for the next generation of space telescopes. Covering most of the wall over her vision table is a panel of micro-thin black plastic shaped like the petal of a giant flower. It’s a reminder of where she’s going: a space mission, still in development, that she believes can lead her to another living Earth.
From an early age, Olivier Guyon has had a problem with sleep: namely, that it’s supposed to happen at night, when it’s so much better to be awake. Guyon grew up in France, in the countryside of Champagne. When he was 11, his parents bought him a small telescope, which he says they later regretted. He spent many nights peering into it, only to fall asleep the next day in class. When he outgrew that telescope, he built a bigger one. But while he could magnify his view of heavenly objects, Guyon could do nothing to enlarge the number of hours in the night. Something had to give, so one day when he was a teenager, he decided to do away with sleep almost entirely. At first he felt great, but after a week or so, he became seriously ill. Recalling it now, he still shudders.
At 43 years old, Guyon today has a very big telescope to work with. The Subaru observatory, along with 12 others, sits atop the summit of Mauna Kea, on Hawaii’s Big Island. The Subaru’s 8.2-meter (27 feet) reflector is among the largest single-piece mirrors in the world. (Operated by the National Astronomical Observatory of Japan, the telescope has no affiliation with the car company—Subaru is the Japanese name for the Pleiades star cluster.) At 13,796 feet above sea level, Mauna Kea affords one of the highest, clearest views of the universe, yet it’s only an hour and a half drive from Guyon’s home in Hilo. The proximity allows him to make frequent trips to test and improve the instrument he built and attached to the telescope, often working through the night. He carries around a thermos of espresso, and for a while he took to spiking it with shots of liquid caffeine, until a friend pointed out that his daily intake was more than half the lethal dose.
“We can spend a couple weeks up here, and we start to forget about life on Earth,” he tells me. “First you forget the day of the week. Then you start forgetting to call your family.”
Like Seager, Guyon is a MacArthur winner. His particular genius is in the mastery of light: how to massage and manipulate it to catch a glimpse of things that even the Subaru’s huge mirror would be blind to without Guyon’s legerdemain.
“The big question is whether there is biological activity up there,” he says, pointing at the sky. “If yes, what is it like? Are there continents? Oceans and clouds? All these questions can be answered, if you can extract the light of a planet from the light of its star.”
In other words, if you can see the planet. Trying to separate the light of a rocky, Earth-size planet from that of its star is like squinting hard enough to make out a fruit fly hovering inches in front of a floodlight. It doesn’t seem possible, and with today’s telescopes, it isn’t. But Guyon has his sights set on what the next generation of ground-based telescopes might be able to do, if they can be fashioned to squint very, very hard.
That is precisely what his instrument is designed to do. The apparatus is called—brace yourself—the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO, pronounced “skex-a-o”). Guyon wanted me to see it in action, but a power outage had shut down the Subaru. Instead he offers to give me a tour of the 141-foot dome enclosing the telescope. There is 40 percent less oxygen here than at sea level. Visitors have the option of strapping on some bottled oxygen, but he decides that I don’t need any, and off we go.
“I was giving a tour the other day to some scientists, and all of a sudden, one of them fainted!” he says, with a mixture of surprise and regret. “I should have known she was not doing well. She had gotten very quiet.” I clutch the railings and make sure to keep asking questions.
Ground telescopes like the Subaru are much more powerful light-gatherers than space telescopes like the Hubble, chiefly because nobody has yet figured out how to squeeze a 27-foot mirror into a rocket and blast it into space. But ground telescopes have a serious drawback: They sit under miles of our atmosphere. Fluctuations in the air’s temperature cause light to bend erratically—think of a twinkling star, or the wavy air above an asphalt road in the summertime.
The first task of the SCExAO is to iron out those wrinkles. This is accomplished by directing the light from a star onto a shape-shifting mirror, smaller than a quarter, activated by 2,000 tiny motors. Using information from a camera, the motors deform the mirror 3,000 times a second to precisely counter the atmospheric aberrations, and voilà, a beam of starlight can be viewed that is as close as possible to what it was before our atmosphere messed it up. Next comes the squinting part. To Guyon, a star’s luminosity is “a boiling blob of light that we’re trying to get rid of.” His instrument includes an intricate system of apertures, mirrors, and masks called a coronagraph, which allows only the light reflected off the planet to slip through.
There’s a great deal more to the apparatus staring at a schematic of the device is enough to cause vertigo, even at sea level. But the eventual result, once the next-gen telescopes are built, will be a visible dot of light that is actually a rocky planet. Shunt this image to a spectrometer, a device that can parse light into its wavelengths, and you can start dusting it for those fingerprints of life, called biosignatures.
There’s one biosignature that Seager, Guyon, and just about everyone else agree would be as near a slam dunk for life as scientific caution allows. We already have a planet to prove it. On Earth, plants and certain bacteria produce oxygen as a by-product of photosynthesis. Oxygen is a flagrantly promiscuous molecule—it’ll react and bond with just about everything on a planet’s surface. So if we can find evidence of it accumulating in an atmosphere, it will raise some eyebrows. Even more telling would be a biosignature composed of oxygen and other compounds related to life on Earth. Most convincing of all would be to find oxygen along with methane, because those two gases from living organisms destroy each other. Finding them both would mean there must be constant replenishment.
It would be grossly geocentric, however, to limit the search for extraterrestrial life to oxygen and methane. Life could take forms other than photosynthesizing plants, and indeed even here on Earth, anaerobic life existed for billions of years before oxygen began to accumulate in the atmosphere. As long as some basic requirements are met—energy, nutrients, and a liquid medium—life could evolve in ways that would produce any number of different gases. The key is finding gases in excess of what should be there.
There are other sorts of biosignatures we can look for too. The chlorophyll in vegetation reflects near-infrared light—the so-called red edge, invisible to human eyes but easily observable with infrared telescopes. Find it in a planet’s biosignature, and you may well have found an extraterrestrial forest. But the vegetation on other planets might absorb different wavelengths of light—there could be planets with Black Forests that are truly black, or planets where roses are red, and so is everything else.
And why stick to plants? Lisa Kaltenegger, who directs the Carl Sagan Institute at Cornell University, and her colleagues have published the spectral characteristics of 137 microorganisms, including ones in extreme Earth environments that, on another planet, might be the norm. It’s no wonder the next generation of telescopes is so eagerly anticipated.
“For the first time, we’ll be able to collect enough light,” says Kaltenegger. “We’ll be able to figure things out.”
The first and most powerful of the next-gen ground telescopes, the European Southern Observatory’s eponymous Extremely Large Telescope (ELT) in the Atacama Desert of Chile, is scheduled to start operation in 2024. The light-gathering capacity of its 39-meter (128 feet) mirror will exceed all existing Subaru-size telescopes combined. Outfitted with a souped-up version of Guyon’s instrument, the ELT will be fully capable of imaging rocky planets in the habitable zone of red dwarf stars, the most common stars in the galaxy. They are smaller and dimmer than our sun, a yellow dwarf, so their habitable zones are closer to the star. The nearer a planet is to its star, the more light it reflects.
Alas, the habitable zone of a red dwarf star is not the coziest place in the galaxy. Red dwarfs are highly energetic, frequently hurtling flares out into space as they progress through what Seager calls a period of “very long, bad, teenage behavior.” There might be ways an atmosphere could evolve that would protect nascent life from being fried by these solar tantrums. But planets around red dwarfs are also likely to be “tidally locked”—always presenting one side to the star, in the same way our moon shows only one face to the Earth. This would render half the planet too hot for life, the other half too cold. The midline, though, might be temperate enough for life.
As it happens, there’s a rocky planet, called Proxima Centauri b, orbiting in the habitable zone of Proxima Centauri, a red dwarf that’s the nearest star to our own, about 4.2 light-years, or 25 trillion miles, away. “It’s a terribly exciting target,” Guyon says. But he agrees with Seager that the best chance of finding life will be on an Earth-like planet orbiting a sunlike star. The ELT and its ilk will be fantastic at gathering light, but even those behemoth ground telescopes won’t be able to separate the light of a planet from that of a star 10 billion times brighter.
That’s going to take a little more time and even more exotic—one might even say dreamlike—technology. Remember that flower petal–shaped panel on Seager’s wall? It’s a piece of a space instrument called Starshade. Its design consists of 28 panels arranged around a center hub like a giant sunflower, more than 100 feet across. The petals are precisely shaped and rippled to deflect the light from a star, leaving a super-dark shadow trailing behind. If a telescope is positioned far back in that tunnel of darkness, it will be able to capture the glimmer from an Earth-like planet visible just beyond the Starshade’s edge.
Starshade’s earliest likely partner is called the Wide Field Infrared Survey Telescope (WFIRST), scheduled to be finished by the mid-2020s. The two spacecraft will work together in a sort of celestial pas de deux: Starshade will amble into position to block the light from a star so WFIRST can detect any planets around it and potentially sample their spectra for signs of life. Then, while WFIRST busies itself with other tasks, Starshade will fly off into position to block the light of the next star on its list of targets. Though the dancers will be tens of thousands of miles apart, they must be aligned to within a single meter for the choreography to work.
Starshade, under development at NASA’s Jet Propulsion Laboratory in Pasadena, California, is still a decade or so away, and indeed there’s no guarantee that it will be funded. Seager, who hopes to lead the project, is confident. One can only hope. There’s something uniquely uplifting about the prospect of a giant flower in space unfurling its petals to parry the light from a distant sun to see if its orbiting worlds are alive.
When Jon Richards answered an ad in 2008 on Craigslist for a software programmer, he couldn’t have imagined he would spend much of the next 10 years in a remote valley in Northern California, looking for aliens. The search for extraterrestrial intelligence, or SETI, refers to both a research endeavor and a nonprofit organization, the SETI Institute, which employs Richards to run the Allen Telescope Array (ATA), a 340-mile drive from the institute’s headquarters in Silicon Valley. The ATA is the only facility on the planet built expressly for detecting signals from alien civilizations. Funded largely by the late Microsoft co-founder Paul Allen, it was envisioned as an assembly of 350 radio telescopes, with dishes six meters (20 feet) in diameter. But owing to funding difficulties—a regrettable leitmotif in SETI history—only 42 have been built. At one time seven scientists helped run the ATA, but due to attrition, Richards is “the last man standing,” as he gamely puts it.
I’ve come to see Richards on a hot day in August, soon after a rash of wildfires in the area. Smoke veils the view of the surrounding mountains, and in the haze the dishes seem primordially still, like Easter Island statues, each one staring implacably at the same spot in a featureless sky. Richards takes me to one of the dishes, opening the bay doors beneath it to reveal its newly installed antenna feed: a crenellated taper of shiny copper housed in a thick glass cone. “Looks kinda like a death ray,” he says.
Richards’s job is to manage the hardware and software, including algorithms developed to sift through the several hundred thousand radio signals streaming into the telescopes every night, in search of a “signal of interest.” Radio frequencies have been the favored hunting ground of SETI since the search for alien transmissions began 60 years ago, largely because they travel most efficiently through space. SETI scientists have focused in particular on a quiet zone in the radio spectrum, free of background noise from the galaxy. It made sense to search in this relatively undisturbed range of frequencies, since that would be where sensible aliens would be most likely to transmit.
Richards tells me that the ATA is working through a target list of 20,000 red dwarfs. In the evening, he makes sure everything is working properly, and while he sleeps, the dishes point, the antennas rouse, photons scuttle through fiber optic cables, and the radio music of the cosmos streams to enormous processors. If a signal passes tests that suggest it stems from neither a natural source nor some quotidian terrestrial one—a satellite, a plane, somebody’s key fob—the computer kicks out an email alert. This being an email he wouldn’t want to miss, Richards has set up his cell service to forward the message to his phone. Conceivably, then, our first contact from an alien civilization could come as a text rattling Richards’s phone on his night table.
So far, however, all the signals of interest have been false alarms. Unlike other experiments, where progress can be made incrementally, SETI is binary: Either extraterrestrials make contact on your watch, or they don’t. Even if they’re out there, the chances that you’re looking in just the right place at just the right time and at just the right radio frequency are remote. Jill Tarter, the retired head of research at SETI, likens the search to dipping a cup in the ocean: The chance you’ll find a fish is exceedingly small, but that doesn’t mean the ocean isn’t full of fish. Unfortunately, Congress long ago lost interest in dipping the cup, abruptly terminating support in 1993.
The good news is that SETI the research endeavor, if not SETI the institute, has recently received a remarkable boost in funding, sending ripples of excitement through the field. In 2015 Yuri Milner, a Russian-born venture capitalist, established the Breakthrough Initiatives, committing at least $200 million to look for life in the universe, including $100 million specifically to search for alien civilizations. Milner was an early investor in Facebook, Twitter, and many other internet companies you wish you’d been an early investor in. Before that, he founded a highly successful internet company in Russia. His philanthropic vision might be summed up as, if we agree that finding evidence for alien intelligence is worth $100 million, why shouldn’t it be his $100 million? “If you look at it that way, it makes sense,” he says, when I meet him in a glitzy watering hole in Silicon Valley. “If it was a billion a year—we should talk.”
Milner is soft-spoken and unobtrusive I hadn’t noticed him arrive until he was standing right next to my chair. He tells me about his background—a degree in physics, a lifelong passion for astronomy, and parents who named him after the cosmonaut Yuri Gagarin, who became the first human in outer space seven months before Milner was born. That was in 1961, which he points out is the same year SETI began. “Everything is interrelated,” he says.
Through one of his initiatives, Breakthrough Listen, he intends to spend $100 million over 10 years, most of it through the SETI Research Center at UC Berkeley. Another project, Breakthrough Watch, is underwriting new technology to search for biosignatures with the European Southern Observatory’s Very Large Telescope in Chile.
Most far out of all—in both senses—is Milner’s Breakthrough Starshot, which is investing $100 million to explore the feasibility of actually going to the nearest star system, Alpha Centauri, which includes the rocky planet Proxima b. Appreciating the magnitude of this challenge requires some perspective. The first Voyager spacecraft, launched in 1977, took 35 years to enter interstellar space. Traveling at that speed, Voyager would need some 75,000 years to reach Alpha Centauri. In the current vision for Starshot, a fleet of pebble-size spaceships hurtling through space at one-fifth the speed of light could reach Alpha Centauri in a mere 20 years. Working from a road map originally proposed by physicist Philip Lubin at UC Santa Barbara, these tiny Niñas, Pintas, and Santa Marías would be propelled by a ground-based laser array, more powerful than a million suns. It may not be possible. But that’s the advantage of private money: Unlike a government program, you’re allowed—expected—to take a big gamble.
“Let’s see in five or 10 years whether it will work,” Milner says, with a shrug. “I’m not an enthusiast in the sense I believe for sure any of this will happen. I’m an enthusiast because it makes sense now to try.”
The day after meeting with Milner, I went to the Berkeley campus to meet the beneficiaries of his Breakthrough Listen largesse. Andrew Siemion, the director of the Berkeley SETI Research Center, is ideally positioned to take the search for intelligent aliens to a new level. In addition to his Berkeley appointment, he has been named to head up SETI investigations at the SETI Institute itself, including operations at the ATA.
Siemion, 38, looks the part of a next-gen SETI master he has a shaved head, a compact build, and a thin gold chain discreetly visible above the buttons of his fitted shirt. While careful to credit the decades of research by Tarter and her colleagues at the SETI Institute, he’s keen to distinguish where SETI is going from where it has been. The initial search was inspired by the possibility of a connection—reaching out in hope of finding someone reaching back. SETI 2.0 is trying to determine whether technological civilization is part of the cosmic landscape, like black holes, gravitational waves, or any other astronomical phenomenon.
“We’re not looking for a signal,” Siemion says. “We’re looking for a property of the universe.”
Breakthrough Listen is by no means abandoning the conventional search for radio transmissions, he tells me on the contrary, it’s doubling down on it, dedicating to SETI roughly a quarter of the viewing time on two huge single-dish radio telescopes in West Virginia and Australia. Siemion is even more excited about a partnership with the new MeerKAT telescope in South Africa, an array of 64 radio dishes, each more than twice the size of the ATA’s. By piggybacking on observations conducted by other scientists, Breakthrough Listen will conduct a 24/7 stakeout of a million stars, dwarfing previous SETI radio searches. Powerful as it is, MeerKAT is just a precursor to radio astronomy’s dream machine: the Square Kilometre Array, which sometime in the next decade will link hundreds of dishes in South Africa with thousands of antennas in Australia, creating the collecting area of a single dish more than a square kilometer, or about 247 acres.
There are other SETI approaches Siemion tells me about—Breakthrough Listen partnerships with telescopes in China, Australia, and the Netherlands, and new technologies in development at Berkeley, the SETI Institute, and elsewhere to look for optical and infrared signals. The gist, echoed by other scientists I talk with, is that SETI is undergoing a transformation from cottage industry to global enterprise.
Most important, empowered and inspired by the accelerating rate of technological development in our own civilization, we are coming to see the target of the quest in a different light. For 60 years we’ve been waiting for ET to phone Earth. But the stark truth is that ET probably has no compelling reason to try to communicate with us, any more than we feel a heartfelt need to extend a greeting to a colony of ants. We may feel technologically mature compared with our past, but compared with what may be out there in the universe, we’re still in diapers. Any civilization that we would be able to detect will likely be millions, perhaps billions, of years ahead of us.
“We’re like trilobites, looking for more trilobites,” says Seth Shostak, a senior astronomer at the SETI Institute.
What we should be looking for is not a message from ET, but signs of ET just going about the business of being ET, alien and intelligent in ways that we may not yet comprehend but may still be able to perceive, by looking for evidence of technology—so-called technosignatures.
The most obvious technosignatures would be ones we’ve produced, or can imagine producing, ourselves. Avi Loeb of Harvard University, who chairs the Breakthrough Starshot advisory board, has noted that if another civilization were using similar laser propulsion to sail through space, its Starshot-like beacons would be visible to the edge of the universe. Loeb also has suggested looking for the spectral signatures of chlorofluorocarbons soiling the atmosphere of aliens who failed to live past the technological diaper stage.
“Based on our own behavior, there must be many civilizations that killed themselves by harnessing technologies that led to their own destruction,” he tells me when I visit him. “If we find them before we destroy our own planet, that would be very informative, something we could learn from.”
On a cheerier note, we could learn a great deal more from civilizations that have solved their energy problem. At a NASA conference on technosignatures (yes, after a quarter century, NASA too is getting back into the SETI game), there was talk about looking for the waste heat from megastructures that we have imagined creating in the future. A Dyson sphere—solar arrays surrounding a star and capturing all of its energy—around our own sun would generate enough power in a second to supply our current demand for a million years. Learning that other civilizations have already accomplished such feats might provide us some hope.
Still, space is vast, and so is time. Even with our ever more powerful computers and telescopes, SETI’s expanded agenda, and the gravity assist of a hundred Yuri Milners, we may never encounter an alien intelligence. On the other hand, the first intimation of life from a distant planet feels thrillingly close.
“You never know what’s going to happen,” Seager says. “But I know that something great is around those stars.”