The mysterious rock that flew past Earth could actually have been an alien spacecraft sailing past us using light, according to a new paper.

When Oumuamua flew past Earth, scientists rushed to learn about it: it was the first known object ever to have made it into our solar system from another. But as they scrambled to research it, the rock made its way out of the other side of our solar system, giving researchers only a glimpse to make the most of.

In that short time, astronomers established that the object was moving strangely. It was spinning very quickly as it flew through the solar system, and seemed to speed up rather than slow down as it went.

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Shape Created with Sketch. Nasa's most stunning pictures of space Show all 30 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. Nasa's most stunning pictures of space 1/30 Solar Flare An image from Nasa's Solar Dynamics Observatory (SDO) shows a 200,000 mile long solar filament ripping through the Sun's corona in September 2013 Nasa 2/30 Nasa Celebrates 50 Years of Spacewalking For 50 years, NASA has been "suiting up" for spacewalking. 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Virts took this photograph of the Gulf of Mexico and U.S. Gulf Coast at sunset Nasa 7/30 Black Hole Friday Nasa celebrated Black Friday by looking into space instead — sharing pictures of black holes Nasa 8/30 NuSTAR X-rays stream off the sun in this image showing observations from by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO) Nasa 9/30 Cassiopeia A c A false colour image of Cassiopeia A comprised with data from the Spitzer and Hubble Space Telescopes and the Chandra X-Ray observatory Nasa 10/30 Orion Capsule splashes down The Orion capsule jetted off into space before heading back a few hours later — having proved that it can be used, one day, to carry humans to Mars Nasa 11/30 Earth Observations From Gemini IV in 1965 This photograph of the Florida Straits and Grand Bahama Bank was taken during the Gemini IV mission during orbit no. 19 in 1965. The Gemini IV crew conducted scientific experiments, including photography of Earth's weather and terrain, for the remainder of their four-day mission following Ed White's historic spacewalk on June 3 12/30 Frosty slopes of Mars This image of an area on the surface of Mars, approximately 1.5 by 3 kilometers in size, shows frosted gullies on a south-facing slope within a crater. The image was taken by Nasa's HiRISE camera, which is mounted on its Mars Reconaissance Orbiter Nasa 13/30 Yellowstone from space NASA astronaut Reid Wiseman shared this image of Yellowstone via his twitter account Nasa 14/30 Saturn This near-infrared color image shows a specular reflection, or sunglint, off of a hydrocarbon lake named Kivu Lacus on Saturn's moon Titan Nasa 15/30 Worlds Apart Although Mimas and Pandora, shown here, both orbit Saturn, they are very different moons. Pandora, "small" by moon standards (50 miles or 81 kilometers across) is elongated and irregular in shape. Mimas (246 miles or 396 kilometers across), a "medium-sized" moon, formed into a sphere due to self-gravity imposed by its higher mass Nasa 16/30 Solar Flare An X1.6 class solar flare flashes in the middle of the sun in this image taken 10 September, captured by NASA's Solar Dynamics Observatory Nasa 17/30 Large Magellanic Cloud galaxy An image of the Large Magellanic Cloud galaxy seen in infrared light by the Herschel Space Observatory. Regions of space such as this are where new stars are born from a mixture of elements and cosmic dust Nasa 18/30 Mars Rover Spirit Nasa's Mars Rover Spirit took the first picture from Spirit since problems with communications began a week earlier. The image shows the robotic arm extended to the rock called Adirondack Nasa 19/30 Morning Aurora From the Space Station Nasa astronaut Scott Kelly captured this photograph of the green lights of the aurora from the International Space Station 20/30 Launch of History - Making STS-41G Mission in 1984 The Space Shuttle Challenger launches from Florida at dawn. On this mission, Kathryn Sullivan became the first U.S. woman to perform a spacewalk and Marc Garneau became the first Canadian in space. The crew of seven was the largest to fly on a spacecraft at that time, and STS-41G was the first flight to include two female astronauts 21/30 A Fresh Perspective on an Extraordinary Cluster of Galaxies Galaxy clusters are often described by superlatives. After all, they are huge conglomerations of galaxies, hot gas, and dark matter and represent the largest structures in the Universe held together by gravity 22/30 Hubble Sees a Galactic Sunflower The arrangement of the spiral arms in the galaxy Messier 63, seen here in an image from the Nasa Hubble Space Telescope, recall the pattern at the center of a sunflower ESA/Hubble & NASA 23/30 Pluto image Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with colour data from the Ralph instrument to create this enhanced colour global view of Pluto 24/30 Fresh Crater Near Sirenum Fossae Region of Mars The HiRISE camera aboard Nasa's Mars Reconnaissance Orbiter acquired this closeup image of a "fresh" (on a geological scale, though quite old on a human scale) impact crater in the Sirenum Fossae region of Mars. This impact crater appears relatively recent as it has a sharp rim and well-preserved ejecta 25/30 Hubble Peers into the Most Crowded Place in the Milky Way This Nasa Hubble Space Telescope image presents the Arches Cluster, the densest known star cluster in the Milky Way NASA & ESA 26/30 An Astronaut's View from Space Nasa astronaut Reid Wiseman tweeted this photo from the International Space Station on 2 September 2014 27/30 Giant Landform on Mars On Mars, we can observe four classes of sandy landforms formed by the wind, or aeolian bedforms: ripples, transverse aeolian ridges, dunes, and what are called “draa” 28/30 Expedition 39 Landing A sokol suit helmet can be seen against the window of the Soyuz TMA-11M capsule shortly after the spacecraft landed with Expedition 39 Commander Koichi Wakata of the Japan Aerospace Exploration Agency (JAXA), Soyuz Commander Mikhail Tyurin of Roscosmos, and Flight Engineer Rick Mastracchio of NASA near the town of Zhezkazgan, Kazakhstan (NASA/Bill Ingalls) 29/30 Jupiter's Great Red Spot Viewed by Voyager I Jupiter is the largest planet in the solar system and perhaps the most majestic. Vibrant bands of clouds carried by winds that can exceed 400 mph continuously circle the planet's atmosphere 30/30 Chandra Observatory Sees a Heart in the Darkness This Chandra X-Ray Observatory image of the young star cluster NGC 346 highlights a heart-shaped cloud of 8 million-degree Celsius gas in the central region

Now a new paper suggests that could be because the object is acting as a "light sail", gliding through space and using the sun as its energy source. If so, that might have happened by accident – or the object might in fact be a spacecraft made by an alien race, they said.

The object might be "a fully operational probe sent intentionally to Earth vicinity by an alien civilisation", the researchers write.

It is not the first time that astronomers have suggested the rock could potentially be an alien spacecraft. Soon after it was discovered, researchers with the Breakthrough Listen project announced they would be monitoring it and seeing if it was sending out radio signals.

The new study, written by Shmuel Bialy and Abraham Loeb from the Harvard Smithsonian Centre for Astrophysics, looks at the way that solar radiation could be used to power the object as it flies through space. They calculate that it would have to be very thin but very wide – and that such a shape would be possible.

If they are right that the object is being propelled by radiation pressure from the sun, then it will be a breakthrough even if it is entirely natural. Such an object would be of a kind never before seen, most likely formed by an entirely unknown process happening deep in space.

But it might in fact be artificial in origin, they write. "One possibility is that �?Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment", the authors claim, and it might be unused debris that has been thrown out into space from a planetary system.

Such an explanation would account for the various strange characteristics of Oumuamua, including the unusual shape it seems to have.

Scientists on Earth have already looked to develop that kind of technology, which would be used to make tiny spacecraft that could be shot through space at intense speed and be pushed only by light. It might already have been developed elsewhere, they write, and could be used for transporting cargo between planets or even between stars.

But even more strange is a theory that the rock could have been sent here on purpose. "Alternatively, a more exotic scenario is that �?Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization," they write.

Oumuamua is now too far away from Earth for scientists to understand any more about it. But more could be found by looking into the solar system for more objects of this type, the authors say – which could happen more in coming years, as new ways of surveying the sky are turned on.</s>On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (AKA 'Oumuamua).

In the months that followed, multiple follow-up observations were conducted that allowed astronomers to get a better idea of its size and shape, while also revealing that it had the characteristics of both a comet and an asteroid.

Interestingly enough, there has also been some speculation that based on its shape, 'Oumuamua might actually be an interstellar spacecraft (Breakthrough Listen even monitored it for signs of radio signals!).

A new study by a pair of astronomers from the Harvard Smithsonian Center for Astrophysics (CfA) has taken it a step further, suggesting that 'Oumuamua may actually be a light sail of extra-terrestrial origin.

The study – "Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?", which recently appeared online – was conducted by Shmuel Bialy and Prof. Abraham Loeb. Whereas Bialy is a postdoctoral researcher at the CfA's Institute for Theory and Computation (ITC), Prof. Loeb is the director of the ITC, the Frank B. Baird Jr. Professor of Science at Harvard University, and the head chair of the Breakthrough Starshot Advisory Committee.

To recap, 'Oumuamua was first spotted by the Pan-STARRS-1 survey 40 days after it made its closest pass to the Sun (on September 9th, 2017).

At this point, it was about 0.25 AU from the Sun (one-quarter the distance between Earth and the Sun), and already on its way out of the Solar System. In that time, astronomers noted that it appeared to have a high density (indicative of a rocky and metallic composition) and that it was spinning rapidly.

While it did not show any signs of outgassing as it passed close to our Sun (which would have indicated that it was a comet), a research team was able to obtain spectra that indicated that 'Oumuamua was more icy than previously thought.

Then, as it began to leave the Solar System, the Hubble Space Telescope snapped some final images of 'Oumuamua that revealed some unexpected behavior.

After examining the images, another international research team discovered that 'Oumuamua had increased in velocity, rather than slowing down as expected. The most likely explanation, they claimed, was that 'Oumuamua was venting material from its surface due to solar heating (AKA outgassing).

The release of this material, which is consistent with how a comet behaves, would give 'Oumuamua the steady push it needed to achieve this boost in velocity.

To this, Bialy and Loeb offer a counter-explanation. If 'Oumuamua were in fact a comet, why then did it not experience outgassing when it was closest to our Sun?

In addition, they cite other research that showed that if outgassing were responsible for the acceleration, it would have also caused a rapid evolution in 'Oumuamua's spin (which was not observed).

Basically, Bialy and Loeb consider the possibility that 'Oumuamua could in fact be a light sail, a form of spacecraft that relies on radiation pressure to generate propulsion – similar to what Breakthrough Starshot is working on. Similar to what is planned for Starshot, this light sail may been sent from another civilization to study our Solar System and look for signs of life. As Prof. Loeb explained to Universe Today via email:

"We explain the excess acceleration of `Oumuamua away from the Sun as the result of the force that the Sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimeter in thickness but tens of meters in size. This makes the object lightweight for its surface area and allows it to act as a light-sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the Solar System)."

Based on this, Bialy and Loeb went about calculating the likely shape, thickness, and mass-to-area ratio that such an artificial object would have. They also attempted to determine whether this object would be able to survive in interstellar space, and whether or not it would be able to withstand the tensile stresses caused by rotation and tidal forces.

What they found was that a sail that was only a fraction of a millimeter thick (0.3-0.9 mm) would be sufficient for a sheet of solid material to survive the journey through the entire galaxy – though this depends greatly on 'Oumuamuam's mass density (which is not well-contrained).

Thick or thin, this sail would be able to withstand collisions with dust-grains and gas that permeate the interstellar medium, as well as centrifugal and tidal forces.

As for what an extra-terrestrial light sail would be doing in our Solar System, Bialy and Loeb offer some possible explanations for that. First, they suggest that the probe may actually be a defunct sail floating under the influence of gravity and stellar radiation, similar to debris from ship wrecks floating in the ocean. This would help explain why Breakthrough Listen found no evidence of radio transmissions.

Loeb further illustrated this idea in a recent article he penned forScientific American, where he suggested that 'Oumuamua could be the first known case of an artificial relic which floated into our Solar System from interstellar space.

What's more, he notes that lightsails with similar dimensions have been designed and constructed by humans, including the Japanese-designed IKAROS project and the Starshot Initiative with which he is involved.

"This opportunity establishes a potential foundation for a new frontier of space archaeology, namely the study of relics from past civilizations in space," Loeb wrote.

"Finding evidence for space junk of artificial origin would provide an affirmative answer to the age-old question 'Are we alone?'. This would have a dramatic impact on our culture and add a new cosmic perspective to the significance of human activity."

On the other hand, as Loeb told Universe Today, 'Oumuamua could be an active piece of alien technology that came to explore our Solar System, the same way we hope to explore Alpha Centauri using Starshot and similar technologies:

"The alternative is to imagine that `Oumuamua was on a reconnaissance mission. The reason I contemplate the reconnaissance possibility is that the assumption that `Oumumua followed a random orbit requires the production of ~10^{15} such objects per star in our galaxy. This abundance is up to a hundred million times more than expected from the Solar System, based on a calculation that we did back in 2009. A surprisingly high overabundance, unless `Oumuamua is a targeted probe on a reconnaissance mission and not a member of a random population of objects."

According to Loeb, that there's also the fact that 'Oumuamua's orbit brought it to within 0.25 AU of the Sun, which is a good orbit for intercepting Earth without experiencing too much solar irradiation. In addition, it came to within 0.15 AU of Earth, which could have been the result of orbital corrections designed to facilitate a flyby.

Alternately, he states that it is possible that hundreds of such probes could be sent so that one of them got close enough to Earth to study it. The fact that the Pan STARRS-1 survey barely detected 'Oumuamua at its closest approach could be seen as an indication that there are many other such objects that were not detected, bolstering the case for 'Oumuamua being one of many such probes.

Considering that astronomers recently concluded that our Solar System has likely captured thousands of interstellar objects like 'Oumuamua, this opens the possibility for future detections which could help prove (or disprove) the case for an interstellar light sail.

Naturally, Bialy and Loeb acknowledge that are still too many unknowns to say with any certainty what 'Oumuamua really is. And even if it does happen to be a piece of natural rock, all other asteroids and comets that have previously been detected have had mass-to-area ratios orders of magnitude larger than the current estimates for 'Oumuamua.

That, and the fact that radiation pressure appears to be capable of accelerating it, would mean that 'Oumuamua represents a new class of thin interstellar material that has never before been seen. If true, that opens up a whole new set of mysteries, such as how such material was produced and by what (or whom).

While it has been beyond the reach of our telescopes for almost a year now, 'Oumuamua is sure to remain the subject of intense study for many years to come. And you can bet astronomers will be on the lookout for more of them! After all, "the Ramans do everything in threes", right?

This article was originally published by Universe Today. Read the original article.</s>A mysterious asteroid called Oumuamua, the first interstellar object ever seen in the solar system, could be a gigantic alien solar sail send to look for signs of life, a new study has claimed.

Astronomers from the Harvard Smithsonian Center for Astrophysics (CfA) analyzed the strange cigar shape of the object, and an unexpected boost in speed and shift in trajectory as it passed through the inner solar system last year.

They concluded that the strange asteroid 'might be a lightsail of artificial origin.'

The study – 'Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?', which recently appeared online – was conducted by Shmuel Bialy, a postdoctoral researcher at the CfA's Institute for Theory and Computation (ITC) and Professor Abraham Loeb, the director of the ITC, the Frank B. Baird Jr. Professor of Science at Harvard University, and the head chair of the Breakthrough Starshot Advisory Committee.

The researchers say the strange acceleration could the the result of solar radiation pushing a giant solar sail.

They found a sail that was only a fraction of a millimeter thick (0.3-0.9 mm) would be sufficient for a sheet of solid material to survive the journey through the entire galaxy.

Lightsails with similar dimensions have been designed and constructed by humans, including the Japanese-designed IKAROS project and the Starshot Initiative with which he is involved.

'Considering an artificial origin, one possibility is that ‘Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment,' they wrote.

'Alternatively, a more exotic scenario is that ‘Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization,' they added.

Another option, which explains the lack of communication, a lack of any kind of signal could mean the giant object is actually an 'alien shipwreck'.

Professor Loeb previously wrote in Scientific American, 'Oumuamua could be the first known case of an artificial relic which floated into our Solar System from interstellar space.

'This opportunity establishes a potential foundation for a new frontier of space archaeology, namely the study of relics from past civilizations in space,'

'Finding evidence for space junk of artificial origin would provide an affirmative answer to the age-old question 'Are we alone?'. This would have a dramatic impact on our culture and add a new cosmic perspective to the significance of human activity.'

Loeb told Universe Today, 'Oumuamua could be an active piece of alien technology that came to explore our Solar System, the same way we hope to explore Alpha Centauri using Starshot and similar technologies'

'The alternative is to imagine that `Oumuamua was on a reconnaissance mission. The reason I contemplate the reconnaissance possibility is that the assumption that `Oumumua followed a random orbit requires the production of ~10^{15} such objects per star in our galaxy. This abundance is up to a hundred million times more than expected from the Solar System, based on a calculation that we did back in 2009. A surprisingly high overabundance, unless `Oumuamua is a targeted probe on a reconnaissance mission and not a member of a random population of objects.'

The cigar-shaped object, named 'Oumuamua, was spotted by the Haleakala observatory in Hawaii on October 19 last year.

A NASA reconstruction of the 'outgassing' of of ′Oumuamua. The cigar-shaped object was first spotted by the Haleakala observatory in Hawaii on October 19 last year. Now a new study claims it could be a solar sail from an alien civilization.

Its appearance and behaviour baffled scientists and led to speculation that it might even be an alien artefact - and now they have found it got a strange speed boost while passing through, which has helped identify it as a comet.

Telescopes first spotted the mysterious red-tinged object last October as it zipped through the inner solar system.

Since then, astronomers have flip-flopped between comet and asteroid for our first confirmed interstellar guest.

'Our high-precision measurements of ′Oumuamua's position revealed that there was something affecting its motion other than the gravitational forces of the Sun and planets,' said Marco Micheli of ESA's (European Space Agency) Space Situational Awareness Near-Earth Object Coordination Centre in Frascati, Italy, and lead author of a paper describing the team's findings.

The speed boost was consistent with the behavior of a comet, said co-author Davide Farnocchia of the Center for Near Earth Object Studies (CNEOS) at NASA's Jet Propulsion Laboratory (JPL).

'This additional subtle force on ′Oumuamua likely is caused by jets of gaseous material expelled from its surface,' said Farnocchia.

'This same kind of outgassing affects the motion of many comets in our solar system.'

Comets normally eject large amounts of dust and gas when warmed by the Sun.

Karen Meech, an astronomer at the University of Hawaii's Institute of Astronomy and co-author of the study, speculated that small dust grains, present on the surface of most comets, eroded away during ′Oumuamua's long journey through interstellar space.

'The more we study ′Oumuamua, the more exciting it gets,' Meech said.

'I'm amazed at how much we have learned from a short, intense observing campaign. I can hardly wait for the next interstellar object!'

′Oumuamua, less than half a mile in length, now is farther away from our Sun than Jupiter and traveling away from the Sun at about 70,000 mph as it heads toward the outskirts of the solar system.

In only another four years, it will pass Neptune's orbit on its way back into interstellar space.

Because ′Oumuamua is the first interstellar object ever observed in our solar system, researchers caution that it's difficult to draw general conclusions about this newly-discovered class of celestial bodies.

However, observations point to the possibility that other star systems regularly eject small comet-like objects and there should be more of them drifting among the stars.

Future ground- and space-based surveys could detect more of these interstellar vagabonds, providing a larger sample for scientists to analyze.</s>The latest theory on ‘Oumuamua comes from a study published on Thursday by Shmuel Bialy and Abraham Loeb, a pair of astronomers with the Harvard Smithsonian Center for Astrophysics.

When scientists reviewed data collected by the Pan-STARRS-1 survey of ‘Oumuamua's closest flyby of the sun on September 9, 2017, they noted that the mysterious rock gained speed, rather than slowing down. Researchers at the time explained that the increase in ‘Oumuamua's velocity was likely explained by outgassing, the release of gas trapped or frozen inside the rock. The object itself was later classified as a comet by officials.

However, this explanation didn't sit right with Bialy and Loeb, who argue that had outgassing been the cause of ‘Oumuamua's increased velocity, it would've sent the interstellar object into a spin, which wasn't observed.

The pair suggested that ‘Oumuamua could actually be a light sail, a spacecraft that relies on radiation pressure for power, that's been sent from an alien civilization looking for signs of life in our solar system.

"We explain the excess acceleration of ‘Oumuamua away from the sun as the result of the force that the sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimeter in thickness but tens of meters in size," Loeb told Universe Today via email.

"This makes the object lightweight for its surface area and allows it to act as a light sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the solar system)."

Bialy and Loeb later explained in their work that should their theory prove true, there is the slight possibility that the light sail could even just be a "defunct sail floating under the influence of gravity and stellar radiation."

But then again, alien civilizations.

"The alternative is to imagine that ‘Oumuamua was on a reconnaissance mission. The reason I contemplate the reconnaissance possibility is that the assumption that ‘Oumumua followed a random orbit requires the production of ~10^{15} such objects per star in our galaxy. This abundance is up to a hundred million times more than expected from the solar system, based on a calculation that we did back in 2009," Loeb wrote.

"A surprisingly high overabundance, unless ‘Oumuamua is a targeted probe on a reconnaissance mission and not a member of a random population of objects."

Questions remain regarding the origin of ‘Oumuamua, and considering the rock is no longer in our solar system and is much too far away for researchers to observe, the lab coats might be in the dark for some time on the matter.</s>Life may exist elsewhere in the Milky Way galaxy, though try as they might, scientists have yet to detect any sign of it. Part of the problem has to do with the size of space; finding traces of organic substances or the waste signatures of alien megastructures isn’t easy at such cosmic distances. Fortunately, there’s the possibility that alien life will come to us in the form of interstellar objects.

By examining interstellar asteroids and comets up close, argues Harvard astronomer Avi Loeb, we might be able to tell whether life exists elsewhere in the Milky Way galaxy—and we could do so without having to leave the cozy confines of our Solar System. Such is Loeb’s astrobiological dream experiment, which he recently described to Gizmodo.

A major benefit of such a mission is that, assuming we find traces of life on an exotic object, we’d have tangible, empirical proof of alien life. This proof of life could come in three forms: microbial or animal life capable of surviving the harsh conditions of space (and possibly even re-entry through a planet’s atmosphere, spreading life elsewhere); the dead remnants of alien life (seen as chemical or biosignatures); or so-called techno-signatures, that is, the technological artifacts left by aliens.

My dream project is to organize a space mission that will land on the surface of trapped interstellar objects within the Solar System and check whether they have signs of life in their interiors. One could also wait for one-time passing objects like `Oumuamua and chase them even though they are unbound to the Sun. This might require some drilling through their outer rocky ice surface. Or, instead of landing on the surface, one can study the composition of the cometary tail (if it exists) behind the object and verify by measuring its oxygen isotope ratio whether its origin is different than the rest of the material in the Solar System. Also with spectroscopy, one can search for organic molecules or biomarkers.

As it stands, both ground- and space-based telescopes aren’t powerful enough to detect traces of life in the atmospheres of distant exoplanets. The next generation of space-based telescopes should be capable of this feat, and they could very well sniff out alien biosignatures. Trouble is, this sort of data would come back in the form of ambiguous light curves, leading to the inevitable controversies of interpretation. At the same time, the prospect of sending probes to a distant star system, while inevitable (fingers crossed), won’t yield results for hundreds if not thousands of years. Loeb further elucidates these concerns:

It is commonly thought that such a search should be conducted using a large telescope aiming to detect biosignatures—molecular products of primitive life in planetary atmospheres, such as molecular oxygen combined with methane—or techno-signatures—artifacts on a planetary surface, such as megastructures or photovoltaic cells—in distant habitable planets, or alternatively by launching a spacecraft that will visit such worlds. The latter approach would take tens of thousands of years using conventional chemical rockets even for the nearest habitable planet, Proxima b. Fortunately, there is a promising alternative that will save this lengthy travel time. Instead of our spacecraft traveling to another star, we can search for objects that were ejected from other planetary systems and spent the lengthy travel time by now on their journey towards us. Even if they were to originate from the nearest star system, Alpha Centauri, these rocks should have started their trip around the time when Homo sapiens came to the scene on Earth about three hundred thousand years ago.

Until recently, the prospect of exploring an interstellar object would’ve seemed absurd. But things changed on October 19, 2017 when astronomers at the Hawaiian Pan-STARRS1 telescope system detected the first known interstellar object to visit our Solar System.

Dubbed ‘Oumuamua, meaning “messenger from afar arriving first” in the indigenous Hawaiian language, the comet-like object blazed through our Solar System at 67,100 miles per hour, while (thankfully) coming no closer to Earth than 20.5 million miles. The cigar-shaped comet or asteroid (astronomers still aren’t entirely sure) didn’t stay for long, departing our Solar System to continue along its epic interstellar journey.



This visit, though brief, grabbed Loeb’s attention:

Prior to ‘Oumuamua’s visit, astronomers could only theorize about the existence of visiting interstellar objects. This messenger from afar arriving first provided actual proof that it can happen—an event that has revitalized the panspermia hypothesis. This is the speculative idea that life on Earth did not emerge spontaneously as per conventional theory, but was instead delivered by incoming asteroids and comets. Let’s say, as a hypothetical, that Mars was once habitable and home to simple microorganisms. A collision with a massive asteroid could have ripped chunks of rock from the Martian surface, sending the rocks—and their biological cargo—toward Earth. After landing, these microbes would “infect” our planet with their DNA, and begin life anew in, literally, an alien environment.

These microorganisms would have to survive extreme temperatures and the vacuum of space, but it might be possible; Earth bacteria can survive in space for prolonged periods, as can tiny tardigrade animals. Incredibly, microorganisms have also been shown capable of surviving re-entry through Earth’s atmosphere, as witnessed by bacteria that survived the Space Shuttle Columbia crash in 2003. These lifeforms would be in a severely dehydrated state, and, at least in theory, could be re-animated once introduced to the right conditions.

The idea that hardy microorganisms can survive long durations through interstellar space may not be as outlandish as it seems, though Loeb admits it’s a stretch:

But even if dead microorganisms were discovered, or just their chemical traces, it would still represent direct evidence for the existence of life beyond our Solar System. These biosignatures could include accumulated piles of microbes (called stromatolites), traces of waste (yep, alien poo), organic compounds containing carbon, nitrogen, and hydrogen, or traces of fat and steroids. Even skeletal fossils could conceivably exist within the rock.

The implications of such a discovery would be huge, to say the least. Finding life on an object of interstellar origin, Loeb argues, would not only demonstrate that life exists elsewhere, but also that it can be transferred between planetary systems—an important next step in validating the panspermia hypothesis.

Another fascinating element to this approach is that some of these interstellar objects could actually be alien spaceships or probes, or even an asteroid with technologies installed onto it. So this wouldn’t be a pure exercise in astrobiology—it also applies to SETI, the Search for Extraterrestrial Intelligence, as Loeb points out:



This possibility occurred to scientists when ‘Oumuamua came through our Solar System. Using the Robert C. Byrd Green Bank Telescope in West Virginia, a team of astronomers from Breakthrough Listen ran several scans of ‘Oumuamua in search of radio signals. None were found, but it was a good idea. Loeb says the discovery of alien techno-signatures on an interstellar object would provide a “resounding affirmative answer” to one of the most fundamental questions in science: “Are we alone?”

Physicist Enrico Fermi asked: “Where is everybody?” suggesting that advanced extra-solar civilizations may not exist because we do not detect obvious signals from them in the sky. But one should keep in mind that the rate of growth in technological knowledge is often proportional to past knowledge. Hence the growth of advanced technologies tends to be exponential. The technological advances may saturate due to the destructive impact of technology, resulting in climate change or nuclear and biological wars. The answer to Fermi’s paradox may be that advanced civilizations are short lived. In this case, we would find relics of dead civilizations, many graveyards on the surfaces of habitable planets but some techno-signatures in the form of strange objects passing through our Solar System, potentially carrying innovative technologies that we have not mastered yet.

Loeb’s dream experiment may be a long shot, but in many ways, it’s quite feasible. We’re actually getting really good at detecting biosignatures and biomarkers within Earth’s oldest rocks, and similar approaches could be used when exploring nearby asteroids and comets. At the same time, next-gen telescopes could be used to sniff out potential biosignatures from afar, as Loeb points out.

And while landing on an asteroid or comet is extremely difficult, scientists are working on it. A mission to an interstellar object would be somewhat similar to the current Japan Hayabusa2 mission, which is scheduled to retrieve surface samples from the Ryugu asteroid and return them to Earth for analysis.

It’s a dream experiment, to be sure, but one grounded in real science.
Astronomers from Harvard University suggest that the interstellar object 'Oumuamua may be an extraterrestrial solar sail from an alien civilization, in an effort to help explain the object's "peculiar acceleration".