It’s always fun to browse through the raw image archive for any Mars mission. You see rocks, dust, more rocks and more dust, but then you see something strange, sitting atop the dirt that is like nothing you’ve seen before.
Once, there was a piece of plastic on the ground in front of Curiosity. Plastic! Not alien plastic though, it was likely something that fell off the rover. Mars rover Opportunity even found strange “blueberries” scattered over Meridiani Planum that turned out to be spherical hematite inclusions, basically little balls of mineral that were formed via water action in Mars’ ancient past.
Now there’s a shiny rock just sitting there, in front of Curiosity.
Mars isn’t known for its shiny objects. Everything is a ruddy color (because of the iron-oxide-laced dust that covers everything) and dull. So, when mission controllers saw this small shiny object, it became a focus of interest. They’ve even named it “Little Colonsay.” Don’t get too excited for an explanation that’s too outlandish, but it will be an interesting find if it turns out to be what scientists think it is.
“The planning team thinks it might be a meteorite because it is so shiny,” writes Susanne Schwenzer, Curiosity mission team member.
Meteorites have been discovered on Mars before by the Mars rovers — and Curiosity is no stranger to finding space rocks strewn on the ground — though it would still be a rare find by Curiosity if it does turn out to be a (likely) metallic chunk of space rock. As pointed out by Schwenzer, the team intend to carry out further analysis of the sample, as well as some other interesting rocks, with Curiosity’s ChemCam instrument to decipher what it’s made of.
So as we welcome the InSight mission to the Red Planet to begin its unprecedented study of Mars’ interior, always remember there’s still plenty of gems sitting on the surface waiting to be found.
After following InSight’s journey and dramatic landing on Mars, I’m now emotionally attached to the space robot.
It’s funny how our perception of the robots we send into space changes with the experiences we have with them. Take NASA’s InSight lander, for example.
I was thrilled to be able to see the mission launch on May 5 from my backyard. I was following the launch feed from my office in the early hours of the morning — lift-off was just after 4 a.m., so I was particularly proud that I hadn’t fallen asleep in my home office. Going outside, I looked to the northwest in hopes of glimpsing the light of the Atlas V-401 rocket as it rose into the dark pre-dawn skies. After I’d seen confirmation via the live-stream video of launch from Vandenburg Air Force Base (130 miles to the northwest of my home in Woodland Hills), I stood precariously on a patio chair to get a better view over my roof and… there it was! A bright plume rising and moving very fast toward the south. And then it was gone; the first ever mission to Mars launched from California was on its way into interplanetary space.
Needless to say, I quickly became invested in this space robot, but before I witnessed its launch from afar, it was another anonymous piece of cold space hardware. As soon as I saw its rocket plume, the mission became “real” and InSight was warmly embedded in my emotions.
NASA likes to play up the dangers of sending missions to Mars — and I can’t blame them; more Mars missions have failed than have succeeded. But in recent years, NASA has beaten the odds and landed all of their surface missions and inserted a bunch of satellites into orbit successfully. The last failed NASA mission to Mars was nearly 20 years ago (the Mars Polar Lander in 1999), everything else since — Mars Odyssey, the two Mars Exploration Rovers, Mars Reconnaissance Orbiter, Phoenix lander (InSight’s twin), Curiosity, MAVEN — have all been resounding successes.
Then, on Monday (Nov. 26), after nearly seven months since I saw it fly over my roof, InSight landed on the dusty surface of Mars.
I was fortunate to be at NASA’s Jet Propulsion Laboratory (JPL) on that day, covering the event for Scientific American and HowStuffWorks, and it was a thrill to be in the hub of all the festivities and spend time with my fellow science communicators. JPL always puts together a great event — whether that be the landing of Curiosity over six years ago, or the sad farewell of Cassini last year — and this was no different. The air was thick with anticipation, and all of the mission scientists, managers and engineers were more than willing to share their stories with the dozens of journalists, reporters, social media peeps and TV crews who were in attendance.
Then it was time for landing.
Sending a mission to Mars is risky and, as already pointed out, in the earlier days of humanity throwing stuff at Mars the majority of the missions failed. So, understandably, everyone had a healthy level of nervousness that there was always a chance that InSight might just make another (expensive) crater in the Martian dirt. But that wasn’t to be. And by all accounts, the landing couldn’t have gone better.
The two Mars Cube One (MarCO) spacecraft that were flying with InSight during its time cruising from Earth became the undisputed silicon heroes of the day. Their purpose was to relay telemetry data from InSight as the lander slammed into the Martian atmosphere to commence its hair-raising entry, descent and landing (EDL) on Mars — a.k.a. the Seven Minutes or Six and a Half Minutes Of Terror, depending on who you talk to. As InSight would be landing in a region where there wouldn’t be a satellite overpass for several hours after landing, MarCO became the relay that, in real time (minus the several minute lag-time that it takes for any signal to travel at the speed of light between Mars and Earth) prevented too many chewed fingernails and passed the message to mission control that the lander had landed safely and everything was, well, just perfect.
In the media area, with a live feed streaming from just next door on the JPL campus, any nervousness evaporated when we all cheered with the mission controllers who were celebrating on the screen. Memories of Curiosity’s landing came flooding back. NASA has done it again, we’re on Mars!
And then, despite warnings that it might be some time before we see the first view of Elysium Planitia from InSight’s camera, we became aware that the mood had changed in mission control. Managers were now huddled around a computer terminal. They were receiving the first image only a few minutes after touch down!
Keep in mind that relaying this image would have been impossible without InSight’s MarCO travel buddies. The success of the mission didn’t depend on MarCO, but they sure made the landing event a more lively celebration, rather than a “yes we’re on Mars, but no pictures until tomorrow!” anticlimax. I asked a couple of the MarCO managers what was next for their robotic heroes, and they said that their mission was complete and that they were a proof of concept “that was now proven.” Apparently, managers for other robotic space missions are planning MarCO-like payloads for future missions. Justifiably so.
Monday was a blur, but I remember walking away from JPL feeling emotional and humbled. Humanity is capable of doing incredible, bold things, I thought to myself. Why can’t we be more like this? Discussing the nature of humanity and our contradictory ways can be saved for another day, however.
Now that we’ve lived InSight’s dramatic journey to Mars, the lander has become more than a robot, it’s a bona fide Mars explorer that, like Curiosity and all the landers and rovers that have come before it, is an extension of the human experience. Designed to live in the Martian environment, InSight has arrived home. Hopes are high for some incredible scientific discoveries about Mars’ interior and its evolution, but I’m also hopeful that the mission will inspire people to embrace our natural urge to explore and discover new things about our universe. This time exploration will be done through the eyes of the newest space robot to join its Martian family, but some time in the next couple of decades, it will be human eyes exploring Elysium Planitia.
For more about the science behind InSight, read my articles for Scientific American and HowStuffWorks.com:
Earth has them. So does the Moon. As does Mars. And now we know dwarf planet Ceres has them, too. Could a Martian moon also have them? Well, according to new research, they could explain the mystery behind Phobos’ strange lines that are carved into its dusty surface.
What am I talking about? Boulders. Specifically boulders that have been on the move. Boulders that — in the presence of a gravitational field, no matter how weak — roll and bounce, leaving their grooves on some of our most beloved celestial bodies.
“These grooves are a distinctive feature of Phobos, and how they formed has been debated by planetary scientists for 40 years,” said planetary scientist Ken Ramsley (Brown University) who led the work, in a statement. “We think this study is another step toward zeroing in on an explanation.”
Ever since NASA’s Mariner and Viking missions spied Phobos’ lines in the 1970’s, scientists have debated what could have created them. The ancient natural satellite of Mars is only 27 kilometers wide and possesses long, etched lines that, in some cases, loop around the entirety of the moon’s circumference.
A popular hypothesis for these lines focused on the possibility that Phobos is a dying moon; the tidal forces from Mars ultimately pulling the body apart. In this scenario, the lines are a sign that the moon’s interior is crumbling, creating fault lines in the surface that our space robots have been able to image. Another idea is that the lines were created by crater chains; multiple impacts by smaller rocks that etched out long lines around Phobos’ surface.
However, according Ramsley’s study, which is published in the journal Planetary and Space Science, the real mechanism that created Phobos’ stripes is far more elegant, and more familiar to us Earthlings. What’s more, it was one of the original hypotheses that was posited when the lines were discovered over 40 years ago.
You see, Phobos has a huge, nine-kilometer-wide crater on one side, called Stickney (named after Angeline Stickney who motivated the search for Mars’ natural satellites in the late 19th Century), that was excavated by a massive impact in the moon’s ancient past. Using computer models, the researchers simulated what would happen post-impact and where the excavated material (including some hefty boulders) would have ended up. Although a huge quantity of material would have been lost to space during the Stickney impact, a few large rocks may have been kicked across the moon’s surface — these boulders would have rolled slowly, slow enough to be held in contact with Phobos, but fast enough, in some cases, to make more than one trip around the moon.
But many of these lines intersect one another and don’t appear to be radially blasted from the crater. Also, there are regions on the surface where the lines entirely disappear. Ramsley’s simulation explains these oddities.
The simulations show that because of Phobos’ small size and relatively weak gravity, Stickney stones just keep on rolling, rather than stopping after a kilometer or so like they might on a larger body. In fact, some boulders would have rolled and bounded their way all the way around the tiny moon. That circumnavigation could explain why some grooves aren’t radially aligned to the crater. Boulders that start out rolling across the eastern hemisphere of Phobos produce grooves that appear to be misaligned from the crater when they reach the western hemisphere.
This also helps to explain why many of these lines cross and superimpose themselves on one another: Grooves that were laid down by boulders rolling immediately after the impact were crossed by boulders that completed a complete traverse of the globe of the moon, some ending up where they started, minutes or hours later. This also explains why Stickney itself has grooves inside its crater basin.
But there’s a blank area on Phobos that appears to contain no grooves, a phenomenon that the simulation also addresses. This region is located at a comparatively low elevation part of Phobos, surrounded by a higher-elevation lip. “It’s like a ski jump,” said Ramsley. “The boulders keep going but suddenly there’s no ground under them. They end up doing this suborbital flight over this zone.
“We think this makes a pretty strong case that it was this rolling boulder model accounts for most if not all the grooves on Phobos.”
As a fan of rolling boulders on other worlds, I particularly enjoy imagining the lumbering slow roll of these massive rocks that circumnavigated Phobos. They had to keep their roll slow so not to achieve escape velocity, but fast enough to leave their indelible marks for humans to ponder their origins.
When rains came to one of the driest places on Earth, an unprecedented mass extinction ensued.
The assumption was that this rainfall would turn this remote region of the Atacama Desert in Chile into a wondrous, floral haven — dormant seeds hidden in the parched landscape would suddenly awake, triggered by the “life-giving” substance they hadn’t seen for centuries — but it instead decimated over three quarters of the native bacterial life, microbes that shun water in favor of the nitrogen-rich compounds the region has locked in its dry soil.
In other words, death fell from the skies.
“We were hoping for majestic blooms and deserts springing to life. Instead, we learned the contrary, as we found that rain in the hyperarid core of the Atacama Desert caused a massive extinction of most of the indigenous microbial species there,” said astrobiologist Alberto Fairen, who works at Cornell Cornell University and the Centro de Astrobiología, Madrid. Fairien is co-author of a new study published in Nature’s Scientific Reports.
“The hyperdry soils before the rains were inhabited by up to 16 different, ancient microbe species. After it rained, there were only two to four microbe species found in the lagoons,” he added in a statement. “The extinction event was massive.”
Climate models suggest that these rains shouldn’t hit the core regions of Atacama more than once every century, though there is little evidence of rainfall for at least 500 years. Because of the changing climate over the Pacific Ocean, however, modern weather patterns have shifted, causing the weird rain events of March 25 and Aug. 9, 2015. It also rained more recently, on June 7, 2017. Besides being yet another reminder about how climate change impacts some of the most delicate ecosystems on our planet, this new research could have some surprise implications for our search for life on Mars.
Over forty years ago, NASA carried out a profound experiment on the Martian surface: the Viking 1 and 2 landers had instruments on board that would explicitly search for life. After scooping Mars regolith samples into their chemical labs and adding a nutrient-rich water mix, one test detected a sudden release of carbon dioxide laced with carbon-14, a radioisotope that was added to the mix. This result alone pointed to signs that Martian microbes in the regolith could be metabolizing the mixture, belching out the CO2.
Alas, the result couldn’t be replicated and other tests threw negative results for biological activity. Scientists have suggested that this false positive was caused by inorganic reactions, especially as, in 2008, NASA’s Phoenix Mars lander discovered toxic and highly reactive perchlorates is likely common all over Mars. Since Viking, no other mission has attempted a direct search for life on Mars and the missions since have focused on seeking out water and past habitable environments rather than directly testing for Mars germs living on modern Mars.
With this in mind, the new Atacama microbe study could shed some light on the Viking tests. Though the out-gassing result was likely a false positive, even if all the samples collected by the two landers contained microscopic Martians, the addition of the liquid mix may well have sterilized the samples — the sudden addition of a large quantity of water is no friend to microbial life that has adapted to such an arid environment.
“Our results show for the first time that providing suddenly large amounts of water to microorganisms — exquisitely adapted to extract meager and elusive moisture from the most hyperdry environments — will kill them from osmotic shock,” said Fairen.
Another interesting twist to this research is that NASA’s Mars rover Curiosity discovered nitrate-rich deposits in the ancient lakebed in Gale Crater. These deposits might provide sustenance to Mars bacteria (and may be a byproduct of their metabolic activity), like their interplanetary alien cousins in Atacama.
As water-loving organisms, humans have traditionally assumed life elsewhere will bare similar traits to life as we know it. But as this study shows, some life on Earth can appear quite alien; the mass extinction event in the high deserts of Chile could teach us about how to (and how not to) seek out microbes on other planets.
When ʻOumuamua visited our solar system last year, the world’s collective interest (and imagination) was firing on all cylinders. Despite astronomers’ insistence that asteroids from other star systems likely zip through the solar system all the time (and the reason why we spotted this one is because our survey telescopes are getting better), there was that nagging sci-fi possibility that ʻOumuamua wasn’t a natural event; perhaps it was an interstellar spaceship piloted by (or at least once piloted by) some kind of extraterrestrial — “Rendezvous With Rama“-esque — intelligence. Alas, any evidence for this possibility has not been forthcoming despite the multifaceted observation campaigns that followed the interstellar vagabond’s dazzling discovery.
Still, I ponder that interstellar visitor. It’s not that I think it’s piloted by aliens, though that would be awesome, I’m more interested in the possibilities such objects could provide humanity in the future. But let’s put ʻOumuamua to one side for now and discuss a pretty nifty project that’s currently in the works and how I think it could make use of asteroids from other stars.
Obviously, this is a long-term goal; humanity is currently having a hard enough time becoming a multiplanetary species, let alone a multistellar species. But from projects like these, new technologies may be developed to solve big problems and those technologies may have novel applications for society today. Central to ESA’s role in the project is an exciting regenerative life-support technology that is inspired by nature, a technology that could reap huge benefits not only for our future hypothetical interstellar space fliers.
Called the MELiSSA (Micro-Ecological Life Support System Alternative) program, scientists are developing a system that mimics aquatic ecosystems on Earth. A MELiSSA pilot plant in Barcelona is capable of keeping rat “crews” alive for months at a time inside an airtight habitat. Inside the habitat is a multi-compartment loop with a “bioreactor” at its core, which consists of algae that produces oxygen (useful for keeping the rats breathing) while scrubbing the air of carbon dioxide (which the rats exhale). The bioreactor was recently tested aboard the International Space Station, demonstrating that the system could be applied to a microgravity environment.
Disclaimer: Space Is Really Big
Assuming that humanity isn’t going to discover faster-than-light (FTL) travel any time soon, we’re pretty much stuck with very pedestrian sub-light-speed travel times to the nearest stars. Even if we assume some sensible iterative developments in propulsion technologies, the most optimistic projections in travel time to the stars is many decades to several centuries. While this is a drag for our biological selves, other research groups have shown that robotic (un-crewed) missions could be done now — after all, Voyager 1 is currently chalking up some mileage in interstellar space and that spacecraft was launched in the 1970’s! But here’s the kicker: Voyager 1 is slow (even if it’s the fastest and only interstellar vehicle humanity has built to date). If Voyager 1 was aimed at our closest star Proxima Centauri (which it’s not), it would take tens of thousands of years to get there.
But say if we could send a faster probe into interstellar space? Projects like Icarus Interstellar and Breakthrough Starshot are approaching this challenge with different solutions, using technology we have today (or technologies that will likely be available pretty soon) to get that travel time down to less than one hundred years.
One… hundred… years.
Sending robots to other stars is hard and it would take generations of scientists to see an interstellar mission through from launch to arrival — which is an interesting situation to ponder. But add human travelers to the mix? The problems just multiplied.
The idea of “worldships” (or generation ships) have been around for many years; basically vast self-sustaining spaceships that allow their passengers to live out their lives and pass on their knowledge (and mission) to the next generation. These ships would have to be massive and contain everything that each generation needs. It’s hard to comprehend what that starship would look like, though DSTART’s concept of hollowing out an asteroid to convert it into an interstellar vehicle doesn’t sound so outlandish. To hollow out an asteroid and bootstrap a self-sustaining society inside, however, is a headache. Granted, DSTART isn’t saying that they are actually going to build this thing (their project website even states: “DSTART is not developing hardware, nor is it building an actual spacecraft”), but they do assume some magic is going to have to happen before it’s even a remote possibility — such as transformative developments in nanotechnology, for example. The life-support system, however, would need to be inspired by nature, so ESA and DSTART scientists are going to continue to help develop this technology for self-sustaining, long-duration missions, though not necessarily for a massive interstellar spaceship.
Hyperbolic Space Rocks, Batman!
Though interesting, my reservation about the whole thing is simple: even if we did build an asteroid spaceship, how the heck would we accelerate the thing? This asteroid would have to be big and probably picked out of the asteroid belt. The energy required to move it would be extreme; to propel it clear of the sun’s gravity (potentially via a series of gravitational assists of other planets) could rip it apart.
So, back to ʻOumuamua.
The reason why astronomers knew ʻOumuamua wasn’t from ’round these parts was that it was moving really, really fast and on a hyperbolic trajectory. It basically barreled into our inner star system, swung off our sun’s gravitational field and slingshotted itself back toward the interstellar abyss. So, could these interstellar asteroids, which astronomers estimate are not uncommon occurrences, be used in the future as vehicles to escape our sun’s gravitational domain?
Assuming a little more science fiction magic, we could have extremely advanced survey telescopes tasked with finding and characterizing hyperbolic asteroids that could spot them coming with years of notice. Then, we could send our wannabe interstellar explorers via rendezvous spacecraft capable of accelerating to great speeds to these asteroids with all the technology they’d need to land on and convert the asteroid into an interstellar spaceship. The momentum that these asteroids would have, because they’re not gravitationally bound to the sun, could be used as the oomph to achieve escape velocity and, once setting up home on the rock, propulsion equipment would be constructed to further accelerate and, perhaps, steer it to a distant target.
If anything, it’s a fun idea for a sci-fi story.
I get really excited about projects like DSTART; they push the limits of human ingenuity and force us to find answers to seemingly insurmountable challenges. Inevitably, these answers can fuel new ideas and inspire younger generations to be bolder and braver. And when these projects start partnering with space agencies to develop existing tech, who knows where they will lead.
If you follow me on Twitter, you’ll probably know my (conflicted) feelings about Elon Musk blasting his cherry red Tesla roadster into space. But there’s one angle of the whole “I’m a billionaire and it’s my rocket company, I can do what the hell I like” saga I hadn’t considered: That same red roadster was carrying a potential biological weapon into space.
Conversely, it might be the biological equivalent of Noah’s Ark.
As the vehicle wasn’t designed (or, indeed, intended) for a planetary encounter (whether that be Mars, Earth or some random asteroid), NASA’s Office of Planetary Protection had no jurisdiction over the test launch of the SpaceX Falcon Heavy from Cape Canaveral, Fla., on Feb. 6. The Tesla roadster acted as the test mass for the launch, outfitted with a space-suited mannequin (or not) — a.k.a. “Starman” — with David Bowie’s “Space Oddity” playing on the radio and a “Don’t Panic” homage to Douglas Adams’ “The Hitchhiker’s Guide to the Galaxy” showing on the car’s display. There was a lot going on with that controversial launch, but no one can dispute that it wasn’t a marketing masterstroke.
As a bonus, I even saw the Falcon upper stage carry out its third burn that evening over Los Angeles during my night run, hours after the Florida launch:
So, back to planetary protection. Or, more precisely, lack thereof.
“Even if they radiated the outside, the engine would be dirty,” said Jay Melosh, professor of earth, atmospheric and planetary sciences at Purdue University, in a statement on Tuesday. “Cars aren’t assembled clean. And even then, there’s a big difference between clean and sterile.”
Also, this wan’t a new car. And no number of details would have removed terrestrial bacteria from the wheels, engine, upholstery and uncountable nooks and crannies bacteria have set up home. And if it’s been driven on Los Angeles roads… well, yuck. Put simply, this car wasn’t subject to the rigorous sterilization procedures spacecraft are subject to.
Space roadster proponents will probably argue that this car isn’t intended to launch a germy invasion party to any planetary body; it was blasted into open space and not likely to hit anything solid for millions of years. It’s just going to be an artificial satellite of the Sun, nothing more.
Bacteria are hardy little buggers and even the frozen radioactive vacuum of space wont be enough to eradicate every microbe from inside that vehicle. Many strains of microbe will simply shut down and hibernate for extreme periods of time until they get heated back up and watered. And, as far as I’m aware, there was no attempt by SpaceX at protecting the extraterrestrial neighborhood from humanity’s germs (besides, why would they?), so there is likely a menagerie of microbial biomass hitching a ride.
Some scientists, being optimistic beings, view this differently, however. Far from being a germ-bomb waiting to smear its humanity’s snot over the pristine slopes of Olympus Mons, the Tesla might actually be a clever way of backing up Earth’s genetic information for the eons to come, regardless of what happens to life on Earth.
“The load of bacteria on the Tesla could be considered a biothreat, or a backup copy of life on Earth,” said Alina Alexeenko, professor of aeronautics and astronautics at Purdue, who specializes in freeze-drying bacteria.
There’s a larger question here, beyond the hype and the probability that the roadster will be a harmless addition to the Sun’s asteroid family; as commercial spaceflight is obviously in its infancy, who’s job is it to ensure payloads are clean? Is it even a priority? Sure, this SpaceX launch won’t likely hit Mars or even Earth, but what about future “test” launches?
Having a bad day? Well, spare a thought for any hypothetical aliens living on Proxima b.
Proxima Centauri is a small, dim M dwarf—commonly known as a red dwarf—located approximately 4.2 light-years away. Over the last couple of years, this diminutive star has spent a lot of time in the headlines after the discovery of a small rocky world, called Proxima b, inside the star’s habitable zone.
With the knowledge that there’s a potentially temperate world on our cosmic doorstep, speculation started to fly that this exoplanet could become a future interstellar destination for humanity or that it’s not just a “habitable” world, perhaps it’s inhabited, too.
Putting aside the fact that we have no idea whether this interesting exoplanet possesses water of any kind, let alone if it even has an atmosphere (two pretty important ingredients for life as we know it), it is certainly an incredible find. But there are some caveats to Proxima b’s habitability and the main one is the unpredictability of its star.
The problem with red dwarfs is that they are angry little stars. In fact, they have long been known as “flare stars” as, well, they produce flares. What they lack in energy output they certainly make up for in explosions. Really, really big explosions.
“March 24, 2017, was no ordinary day for Proxima Cen,” said astronomer Meredith MacGregor, of the Carnegie Institution for Science in Washington D.C., in a statement.
Over just ten seconds on that special day, a powerful flare boosted Proxima Centauri’s brightness by over 1,000 times greater than normal. This mega-flare event was preceded by a smaller flare event and both flares occurred over a two minute period.
Although astronomers have little idea where Proxima b was in relation to the flaring site, it would have undoubtedly received one hell of a radiation dose from the eruption.
“It’s likely that Proxima b was blasted by high energy radiation during this flare,” said MacGregor. “Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilized the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water.”
The habitable zone around any star is the distance at which a world must orbit to receive just the right amount of energy to maintain water in a liquid state. Liquid water, as we all know, is necessary for life (as we know it) to evolve. Whereas the Earth orbits the Sun at an average distance of nearly 100 million miles (a distance that unsurprisingly puts us inside our star’s habitable zone), for a star as cool as Proxima Centauri, its habitable zone is closer. Much, much closer. This means Proxima b, with an orbital distance of approximately 4.6 million miles, is nearly 22 times closer to its star than the Earth is to the Sun. Orbiting so close to a star pumping out a flare ten times more powerful than the largest flare our Sun can generate is the space weather equivalent of sitting inside the blast zone of a nuclear weapon.
As MacGregor argues, Proxima Centauri is known to generate these kinds of flares, and Proxima b has been bathed in its radiation for eons. It doesn’t seem likely that the exoplanet would be able to form an atmosphere, let alone hold onto one.
So, what of Proxima b’s hypothetical aliens? Well, unless they’ve found a niche deep under layers of ice and/or rock, it seems that this “habitable” world is anything but.
If you thought detecting small planets orbiting stars dozens of light-years distant was impressive, imagine trying to “see” individual comets zoom around their star. Well, astronomers have done just that after poring over 201,250 targets in the Kepler dataset.
NASA’s Kepler mission has been taking observational data since 2009, staring unblinkingly at a small area of sky in the direction of the constellation Cygnus until it transitioned into the K2 mission in 2013. In total, the space telescope has discovered over 2,500 confirmed exoplanets (and over 5,000 candidate exoplanets), transforming our understanding of the incredible menagerie of alien worlds in our galaxy. After including discoveries by other observatories, we know of over 3,500 exoplanets that are out there.
Kepler detects exoplanets by watching out for periodic dips in the brightness of stars in its field of view. Should a slight dip in brightness be detected, it could mean that there’s an exoplanet orbiting in front of its host star—an event known as a “transit.” While these transits can help astronomers learn about the physical size of exoplanets and the period of their orbits, for example, there’s much more information in the transit data than initially meets the eye.
In a new study to be published in the journal Monthly Notices of the Royal Astronomical Society on Feb. 21, a team of researchers are reporting that they have found evidence for individual comets transiting in front of two stars. They detected six individual transits at the star KIC 3542116, which is located approximately 800 light-years from Earth, and one transit at KIC 11084727. Both stars of a similar type (F2V) and are quite bright.
Though other observations have revealed dusty evidence of cometary activity in other star systems before, this is the first time individual comets have been found leaving their own transit signal in Kepler data. And it turns out that their transit fingerprint is a little bit special:
“The transits have a distinct asymmetric shape with a steeper ingress and slower egress that can be ascribed to objects with a trailing dust tail passing over the stellar disk,” the astronomers write in their paper (arXiv preprint). “There are three deeper transits with depths of ≃ 0.1 percent that last for about a day, and three that are several times more shallow and of shorter duration.”
In other words, when compared with the transit of an exoplanet, comet transits appear wonky (or asymmetric). This is because comets possess tails of gas and dust that trail the nucleus; as the comet passes in front of its star, starlight is quickly blocked, but as it drifts by in its orbit, the dusty tail will act as a starlight dimmer, gradually allowing more starlight to be seen by Kepler. An exoplanet—or, indeed, any spherical object without a dusty tail—will create a symmetrical dip in the transit signal. Other possible causes of this unique transit signal (such as starspots and instrumental error) were systematically ruled out. (Interestingly, in a 1999 Astronomy & Astrophysics paper, this asymmetric comet transit signal was predicted by another team of researchers, giving this current work some extra certainty.)
But just because there was evidence of six comet transits at KIC 3542116, it doesn’t mean there were six comets. Some of those transits could have been caused by the same comet, so the researchers have hedged their bets, writing: “We have tentatively postulated that these are due to between 2 and 6 distinct comet-like bodies in the system.”
Using these transit data, the study also takes a stab at how big these comets are and even estimates their orbital velocities. The researchers calculate that these comets have masses that are comparable to Halley’s Comet, the famous short-period comet that orbits the sun every 74-79 years and was last visible from Earth in 1986. For the deeper transits (for KIC 3542116 and the single transit at KIC 11084727), they estimate that the comets causing those transits are travelling at speeds of between 35 to 50 kilometers per second (22 to 31 miles per second). For the shallow, narrow transits at KIC 3542116, the inferred speeds are between 75 to 90 kilometers per second (47 to 56 miles per second).
“From these speeds we can surmise that the corresponding orbital periods are ⪆ 90 days (and most probably, much longer) for the deeper transits, and ⪆ 50 days for the shorter events,” they write.
But the fact that comets were detected at two similar F2V-type stars gives the researchers pause. Is there something special about these stars that means there’s more likelihood of possessing comets? Or is it just chance? Also, the fact that these comet transits were identified by visually analyzing the Kepler datasets suggests that there are likely many more transits hiding in the archived Kepler observations.
One thing’s for sure: this is a mind-blowing discovery that underscores just how valuable exoplanet-hunting missions are for probing the environment around other stars and not just for discovering strange new worlds. I’m excited for what other discoveries are waiting in Kepler transit data and for future exoplanet-hunting missions such as NASA’s Transiting Exoplanet Survey Satellite (TESS) that is scheduled for launch this year.
If you were hoping that the bizarre transit signals coming from Tabby’s Star were signs of a massive alien construction site, you’d better sit down.
A new study published in Astrophysical Journal Letters today documents a highly-detailed astronomical study of the star, concluding that this stellar oddity is driven by natural phenomena and most likely not caused by an extraterrestrial intelligence.
Since citizen scientists of the exoplanet project Planet Hunters identified the odd transit signal of KIC 8462852 from publicly-available data collected by NASA’s Kepler Space Telescope in 2015, the world has been captivated by what it means. Though KIC 8462852 is a fairly average star as stars go, it exhibited inexplicable dimming events that have never been seen before.
Finding something extraordinary in deep space is often followed by extraordinary explanations, including the possibility that some super-advanced alien civilization is building a “megastructure” around its star. Over time, more rational hypotheses have been ruled out, but how do you rule out aliens fiddling with their star’s brightness? Well, that’s taken a little more time.
Now, thanks to a study headed by astronomer Tabetha Boyajian of Louisiana State University in Baton Rouge, it seems the alien megastructure hypothesis has bitten the dust, literally.
“Dust is most likely the reason why the star’s light appears to dim and brighten,” Boyajian said in a statement. “The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure.”
As you’d expect, if something solid (like a massive Alien Made™ solar energy collector) were to pass in front of a star, all wavelengths of light would be stopped at the same time. The fact that the dimming events are wavelength (brightness) dependent suggests that whatever is blocking the starlight isn’t a solid mass.
Boyajian, Tabby’s Star’s namesake who led the team that discovered the stellar dimming phenomenon, and her team of over 100 astronomers carried out an unprecedented observation campaign on the star from March 2016 to December 2017 using the Las Cumbres Observatory network. The project was supported by a Kickstarter campaign that raised $100,000 from 1,700 backers.
During the campaign, four distinct dimming events were detected at Tabby’s Star and each were given names by the project’s crowdfunding community. Starting in May 2017, the first two dips were named “Elsie” and “Celeste,” and the second two were named after the lost cities of Scotland’s “Scara Brae” and Cambodia’s “Angkor.”
“They’re ancient; we are watching things that happened more than 1,000 years ago. They’re almost certainly caused by something ordinary, at least on a cosmic scale. And yet that makes them more interesting, not less. But most of all, they’re mysterious.” — from “The First Post-Kepler Brightness Dips of KIC 8462852,” ApJL, 2018
Although the story of the alien megastructure may be coming to an end, this astronomical saga has been an incredible success for science outreach and public engagement with citizen science projects, like Planet Hunters. In this incredible age of astronomy where there’s simply too much data to analyse, scientists are increasingly turning to the public for help in making groundbreaking discoveries.
“If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked,” added Boyajian. “Again, without the public support for this dedicated observing run, we would not have this large amount of data.”
So, the search continues and I, for one, am excited for the next “alien megastructure” mystery …
Fortunately for life on Earth, our planet has an ozone layer. This high-altitude gas performs an invaluable service to biology, acting as a kind of global “sunscreen” that blocks the most damaging forms of ultraviolet radiation. Early in the evolution of terrestrial life, if there were no ozone layer, life would have found it difficult to gain a foothold.
So, in our effort to seek out exoplanets that are suitable for life, future telescopes will seek out so-called “biosignatures” in the atmospheres of alien worlds. Astrobiologists would be excited to find ozone in particular — not only for its biology-friendly, UV-blocking abilities, but also because the molecule’s building blocks (three oxygen atoms) can originate from biological activity on the planet’s surface.
Recently, two exoplanets have taken the science news cycle by storm. The first, Proxima b, is touted as the closest temperate exoplanet beyond our solar system. Located a mere 4.22 light-years from Earth, this (presumably) rocky world orbits its star, Proxima Centauri, at just the right distance within the habitable zone. Should this world possess an atmosphere, it would receive just the right amount of energy for any water on its surface to exist in a liquid state. As liquid water is essential for life on Earth, logic dictates that life may be possible there too.
Whether or not Proxima b has the right orbit about its star is academic; there are many other factors to consider before calling it “Earth-like.” For starters, habitable zone exoplanets around red dwarfs will be “tidally locked.” Tidal locking occurs because red dwarf habitable zones are very close to the cool star; so to receive the same amount of heating as our (obviously) habitable Earth, habitable exoplanets around red dwarfs need to cuddle up close. And because they are so close, the same hemisphere will always face the star, while the other hemisphere will always face away. These strange worlds are anything but “Earth-like.”
Also, Proxima Centauri is an angry little star, blasting its locale with regular flares, irradiating its interplanetary space with X-rays, UV and high-energy particles — things that will strip atmospheres from planets and drench planetary surfaces with biology-wrecking radiation. As I’ve previously written, Proxima b is likely a hellhole. And things don’t bode well for that other “habitable” exoplanet TRAPPIST-1d, either.
It’s a Trap
But let’s just say, for astrobiology-sake, that a tidally-locked world orbiting a red dwarf does host an atmosphere and an alien biosphere has managed to evolve despite these stellar challenges. This biosphere is also pretty Earth-like in that oxygen-producing lifeforms are there and the planetary atmosphere has its own ozone layer. As previously mentioned, ozone would be a pretty awesome molecule to find (in conjunction with other biosignatures). But what if no ozone is detected? Well, according to Ludmila Carone, of the Max Planck Institute for Astronomy in Germany, and her team, not finding detecting ozone doesn’t necessarily mean it’s not there, it’s just that the atmospheric dynamics of tidally-locked worlds are very different to Earth’s.
“Absence of traces of ozone in future observations does not have to mean there is no oxygen at all,” said Carone in a statement. “It might be found in different places than on Earth, or it might be very well hidden.”
Earth’s ozone is predominantly produced at the equator where sun-driven chemical reactions occur high in the atmosphere. Atmospheric flows then transport chemicals like ozone toward the poles, giving our planet a global distribution. When carrying out simulations of tidally-locked worlds, however, Carone’s team found that atmospheric flows may operate in reverse, where atmospheric flows travel from the poles to the equator. Therefore, any ozone produced at the equator will become trapped there, greatly reducing our ability to detect it.
“In principle, an exoplanet with an ozone layer that covers only the equatorial region may still be habitable,” added Carone. “Proxima b and TRAPPIST-1d orbit red dwarfs, reddish stars that emit very little harmful UV light to begin with. On the other hand, these stars can be very temperamental, and prone to violent outbursts of harmful radiation including UV.”
So the upshot is, until we have observatories powerful enough to study these hypothetical exoplanetary atmospheres — such as NASA’s James Webb Space Telescope (JWST) or the ESO’s Extremely Large Telescope (ELT) — we won’t know. But modelling the hypothetical atmospheres of these very alien worlds will help us understand what we will, or won’t, see in the not-so-distant future.
“We all knew from the beginning that the hunt for alien life will be a challenge,” said Carone. “As it turns out, we are only just scratching the surface of how difficult it really will be.”