Last week, an incredible announcement was made about the search for extraterrestrial life: Phosphine gas detected in the clouds of Venus – a potential indicator of life or “biosignature.” Now some gases might be a false positive for biosignatures because they can be created by other chemical processes on a planet like photochemical processes in the atmosphere or geological processes beneath the surface that create a given gas. For example, methane can also be a biosignature, and we’ve been hunting it down on Mars, but we know that methane can also be created geologically. Finding phosphine in Venusian clouds is truly remarkable because we don’t presently know of any way to create phosphine abiotically or without life being a part of the equation. Question is – how much life??
Scientists have speculated that given the sheer number of galaxies in our Universe – modern estimates are as high as 2 trillion – that there must be infinite opportunities for life to emerge. It has also been theorized that galaxies (like stars) have habitable zones, where star systems located too close to the core or too far out in the spiral arms will be exposed to too much radiation for life to emerge.
But are certain types of galaxies more likely to produce intelligent life? Not that long ago, scientists believed that giant elliptical galaxies – which are substantially larger than spiral galaxies (like the Milky Way) – are a far more likely place to find advanced civilizations. But according to new research from the University of Arkansas, these galaxies may not be the cradles of civilization they were previously thought to be.
As you probably know, NASA recently announced plans to send a mission to Jupiter’s moon Europa. If all goes well, the Europa Clipper will blast off for the world in the 2020s, and orbit the icy moon to discover all its secrets.
And that’s great and all, I like Europa just fine. But you know where I’d really like us to go next? Titan.
Titan, as you probably know, is the largest moon orbiting Saturn. In fact, it’s the second largest moon in the Solar System after Jupiter’s Ganymede. It measures 5,190 kilometers across, almost half the diameter of the Earth. This place is big.
It orbits Saturn every 15 hours and 22 days, and like many large moons in the Solar System, it’s tidally locked to its planet, always showing Saturn one side.
Before NASA’s Voyager spacecraft arrived in 1980, astronomers actually thought that Titan was the biggest moon in the Solar System. But Voyager showed that it actually has a thick atmosphere, that extends well into space, making the true size of the moon hard to judge.
This atmosphere is one of the most interesting features of Titan. In fact, it’s the only moon in the entire Solar System with a significant atmosphere. If you could stand on the surface, you would experience about 1.45 times the atmospheric pressure on Earth. In other words, you wouldn’t need a pressure suit to wander around the surface of Titan.
You would, however, need a coat. Titan is incredibly cold, with an average temperature of almost -180 Celsius. For you Fahrenheit people that’s -292 F. The coldest ground temperature ever measured on Earth is almost -90 C, so way way colder.
You would also need some way to breathe, since Titan’s atmosphere is almost entirely nitrogen, with trace amounts of methane and hydrogen. It’s thick and poisonous, but not murderous, like Venus.
Titan has only been explored a couple of times, and we’ve actually only landed on it once.
The first spacecraft to visit Titan was NASA’s Pioneer 11, which flew past Saturn and its moons in 1979. This flyby was followed by NASA’s Voyager 1 in 1980 and then Voyager 2 in 1981. Voyager 1 was given a special trajectory that would take it as close as possible to Titan to give us a close up view of the world.
Voyager was able to measure its atmosphere, and helped scientists calculate Titan’s size and mass. It also got a hint of darker regions which would later turn out to be oceans of liquid hydrocarbons.
The true age of Titan exploration began with NASA’s Cassini spacecraft, which arrived at Saturn on July 4, 2004. Cassini made its first flyby of Titan on October 26, 2004, getting to within 1,200 kilometers or 750 miles of the planet. But this was just the beginning. By the end of its mission later this year, Cassini will have made 125 flybys of Titan, mapping the world in incredible detail.
Cassini saw that Titan actually has a very complicated hydrological system, but instead of liquid water, it has weather of hydrocarbons. The skies are dotted with methane clouds, which can rain and fill oceans of nearly pure methane.
And we know all about this because of Cassini’s Huygen’s lander, which detached from the spacecraft and landed on the surface of Titan on January 14, 2005. Here’s an amazing timelapse that shows the view from Huygens as it passed down through the atmosphere of Titan, and landed on its surface.
Huygens landed on a flat plain, surrounded by “rocks”, frozen globules of water ice. This was lucky, but the probe was also built to float if it happened to land on liquid instead.
It lasted for about 90 minutes on the surface of Titan, sending data back to Earth before it went dark, wrapping up the most distant landing humanity has ever accomplished in the Solar System.
Although we know quite a bit about Titan, there are still so many mysteries. The first big one is the cycle of liquid. Across Titan there are these vast oceans of liquid methane, which evaporate to create methane clouds. These rain, creating mists and even rivers.
Is it volcanic? There are regions of Titan that definitely look like there have been volcanoes recently. Maybe they’re cryovolcanoes, where the tidal interactions with Saturn cause water to well up from beneath crust and erupt onto the surface.
Is there life there? This is perhaps the most intriguing possibility of all. The methane rich system has the precursor chemicals that life on Earth probably used to get started billions of years ago. There’s probably heated regions beneath the surface and liquid water which could sustain life. But there could also be life as we don’t understand it, using methane and ammonia as a solvent instead of water.
To get a better answer to these questions, we’ve got to return to Titan. We’ve got to land, rove around, sail the oceans and swim beneath their waves.
Now you know all about this history of the exploration of Titan. It’s time to look at serious ideas for returning to Titan and exploring it again, especially its oceans.
Planetary scientists have been excited about the exploration of Titan for a while now, and a few preliminary proposals have been suggested, to study the moon from the air, the land, and the seas.
First up, there’s the Titan Saturn System Mission, a mission proposed in 2009, for a late 2020s arrival at Titan. This spacecraft would consist of a lander and a balloon that would float about in the atmosphere, and study the world from above. Over the course of its mission, the balloon would circumnavigate Titan once from an altitude of 10km, taking incredibly high resolution images. The lander would touch down in one of Titan’s oceans and float about on top of the liquid methane, sampling its chemicals.
As we stand right now, this mission is in the preliminary stages, and may never launch.
In 2012, Dr. Jason Barnes and his team from the University of Idaho proposed sending a robotic aircraft to Titan, which would fly around in the atmosphere photographing its surface. Titan is actually one of the best places in the entire Solar System to fly an airplane. It has a thicker atmosphere and lower gravity, and unlike the balloon concept, an airplane is free to go wherever it needs powered by a radioactive thermal generator.
Although the mission would only cost about $750 million or so, NASA hasn’t pushed it beyond the conceptual stage yet.
An even cooler plan would put a boat down in one of Titan’s oceans. In 2012, a team of Spanish engineers presented their idea for how a Titan boat would work, using propellers to put-put about across Titan’s seas. They called their mission the Titan Lake In-Situ Sampling Propelled Explorer, or TALISE.
Propellers are fine, but it turns out you could even have a sailboat on Titan. The methane seas have much less density and viscosity than water, which means that you’d only experience about 26% the friction of Earth. Cassini measured windspeeds of about 3.3 m/s across Titan, which half the average windspeed of Earth. But this would be plenty of wind to power a sail when you consider Titan’s thicker atmosphere.
And here’s my favorite idea. A submarine. This 6-meter vessel would float on Titan’s Kraken Mare sea, studying the chemistry of the oceans, measuring currents and tides, and mapping out the sea floor.
It would be capable of diving down beneath the waves for periods, studying interesting regions up close, and then returning to the surface to communicate its findings back to Earth. This mission is in the conceptual stage right now, but it was recently chosen by NASA’s Innovative Advanced Concepts Group for further study. If all goes well, the submarine would travel to Titan by 2038 when there’s a good planetary alignment.
Okay? Are you convinced? Let’s go back to Titan. Let’s explore it from the air, crawl around on the surface and dive beneath its waves. It’s one of the most interesting places in the entire Solar System, and we’ve only scratched the surface.
If I’ve done my job right, you’re as excited about a mission to Titan as I am. Let’s go back, let’s sail and submarine around that place. Let me know your thoughts in the comments.
Ask me my favorite object in the Solar System, especially to see through a telescope, and my answer is always the same: Saturn.
Saturn is this crazy, ringed world, different than any other place we’ve ever seen. And in a small telescope, you can really see the ball of the planet, you can see its rings. It’s one thing to see a world like this from afar, a tiny jumping image in a telescope. To really appreciate and understand a place like Saturn, you’ve got to visit.
And thanks to NASA’s Cassini spacecraft, that’s just what we’ve been doing for the last 13 years. Take a good close look at this amazing ringed planet and its moons, and studying it from every angle.
Throughout this article, I’m going to regale you with the amazing discoveries made by Cassini at Saturn. What it taught us, and what new mysteries it uncovered.
NASA’s Cassini spacecraft was launched from Earth on October 15, 1997. Instead of taking the direct route, it made multiple flybys of Venus, a flyby of Earth and a flyby of Jupiter. Each one of these close encounters boosted Cassini’s velocity, allowing it to make the journey with less escape velocity from Earth.
It arrived at Saturn on July 1st, 2004 and began its science operations shortly after that. The primary mission lasted 4 years, and then NASA extended its mission two more times. The first ending in 2010, and the second due to end in 2017. But more on that later.
Before Cassini, we only had flybys of Saturn. NASA’s Pioneer 11, and Voyagers 1 and 2 both zipped past the planet and its moons, snapping pictures as they went.
But Cassini was here to stay. To orbit around and around the planet, taking photos, measuring magnetic fields, and studying chemicals.
For Saturn itself, Cassini was able to make regular observations of the planet as it passed through entire seasons. This allowed it to watch how the weather and atmospheric patterns changed over time. The spacecraft watched lightning storms dance through the cloudtops at night.
Two highlights. In 2010, Cassini watched a huge storm erupt in the planet’s northern hemisphere. This storm dug deep into Saturn’s lower atmosphere, dredging up ice from a layer 160 kilometers below and mixing it onto the surface. This was the first time that astronomers were able to directly study this water ice on Saturn, which is normally in a layer hidden from view.
The second highlight, of course, is the massive hexagonal storm churning away in Saturn’s northern pole. This storm was originally seen by Voyager, but Cassini brought its infrared and visible wavelength instruments to bear.
Why a hexagon? That’s still a little unclear, but it seems like when you rotate fluids of different speeds, you get multi-sided structures like this.
Cassini showed how the hexagonal storm has changed in color as Saturn moved through its seasons.
This is one of my favorite images sent back by Cassini. It’s the polar vortex at the heart of the hexagon. Just look at those swirling clouds.
Now, images of Saturn itself are great and all, but there was so much else for Cassini to discover in the region.
Cassini studied Saturn’s rings in great detail, confirming that they’re made up of ice particles, ranging in size as small a piece of dust to as large as a mountain. But the rings themselves are actually quite thin. Just 10 meters thick in some places. Not 10 kilometers, not 10 million kilometers, 10 meters, 30 feet.
The spacecraft helped scientists uncover the source of Saturn’s E-ring, which is made up of fresh icy particles blasting out of its moon Enceladus. More on that in a second too.
Here’s another one of my favorite images of the mission. You’re looking at strange structures in Saturn’s B-ring. Towering pillars of ring material that rise 3.5 kilometers above the surrounding area and cast long shadows. What is going on here?
They’re waves, generated in the rings and enhanced by nearby moons. They move and change over time in ways we’ve never been able to study anywhere else in the Solar System.
Cassini has showed us that Saturn’s rings are a much more dynamic place than we ever thought. Some moons are creating rings, other moons are absorbing or distorting them. The rings generate bizarre spoke patterns larger than Earth that come and go because of electrostatic charges.
Speaking of moons, I’m getting to the best part. What did Cassini find at Saturn’s moons?
Let’s start with Titan, Saturn’s largest moon. Before Cassini, we only had a few low resolution images of this fascinating world. We knew Titan had a dense atmosphere, filled with nitrogen, but little else.
Cassini was carrying a special payload to assist with its exploration of Titan: the Huygens lander. This tiny probe detached from Cassini just before its arrival at Saturn, and parachuted through the cloudtops on January 14, 2005, analyzing all the way. Huygens returned images of its descent through the atmosphere, and even images of the freezing surface of Titan.
But Cassini’s own observations of Titan took the story even further. Instead of a cold, dead world, Cassini showed that it has active weather, as well as lakes, oceans and rivers of hydrocarbons. It has shifting dunes of pulverized rock hard water ice.
If there’s one place that needs exploring even further, it’s Titan. We should return with sailboats, submarines and rovers to better explore this amazing place.
We learned, without a shadow of a doubt, that Mimas absolutely looks like the Death Star. No question. But instead of a megalaser, this moon has a crater a third of its own size.
Cassini helped scientists understand why Saturn’s moon Iapetus has one light side and one dark side. The moon is tidally locked to Saturn, its dark side always leading the moon in orbit. It’s collecting debris from another Saturnian moon, Phoebe, like bugs hitting the windshield of a car.
Perhaps the most exciting discovery that Cassini made during its mission is the strange behavior of Saturn’s moon Enceladus. The spacecraft discovered that there are jets of water ice blasting out of the moon’s southern pole. An ocean of liquid water, heated up by tidal interactions with Saturn, is spewing out into space.
And as you know, wherever we find water on Earth, we find life. We thought that water in the icy outer Solar System would be hard to reach, but here it is, right at the surface, venting into space, and waiting for us to come back and investigate it further.
On September 15, 2017, the Cassini mission will end. How do we know it’s going to happen on this exact date? Because NASA is going to crash the spacecraft into Saturn, killing it dead.
That seems a little harsh, doesn’t it, especially for a spacecraft which has delivered so many amazing images to us over nearly two decades of space exploration? And as we’ve seen from NASA’s Opportunity rover, still going, 13 years longer than anticipated. Or the Voyagers, out in the depths of the void, helping us explore the boundary between the Solar System and interstellar space. These things are built to last.
The problem is that the Saturnian system contains some of the best environments for life in the Solar System. Saturn’s moon Enceladus, for example, has geysers of water blasting out into space.
Cassini spacecraft is covered in Earth-based bacteria and other microscopic organisms that hitched a ride to Saturn, and would be glad to take a nice hot Enceladian bath. All they need is liquid water and a few organic chemicals to get going, and Enceladus seems to have both.
NASA feels that it’s safer to end Cassini now, when they can still control it, than to wait until they lose communication or run out of propellant in the future. The chances that Cassini will actually crash into an icy moon and infect it with our Earth life are remote, but why take the risk?
For the last few months, Cassini has been taking a series of orbits to prepare itself for its final mission. Starting in April, it’ll actually cross inside the orbit of the rings, getting closer and closer to Saturn. And on September 15th, it’ll briefly become a meteor, flashing through the upper atmosphere of Saturn, gone forever.
Even in its final moments, Cassini is going to be sciencing as hard as it can. We’ll learn more about the density of consistency of the rings close to the planet. We’ll learn more about the planet’s upper atmosphere, storms and clouds with the closest possible photographs you can take.
And then it’ll all be over. The perfect finale to one of the most successful space missions in human history. A mission that revealed as many new mysteries about Saturn as it helped us answer. A mission that showed us not only a distant alien world, but our own planet in perspective in this vast Solar System. I can’t wait to go back.
How have the photos from Cassini impacted your love of astronomy? Let me know your thoughts in the comments.
Perhaps the most important question we can possible ask is, “are we alone in the Universe?”.
And so far, the answer has been, “I don’t know”. I mean, it’s a huge Universe, with hundreds of billions of stars in the Milky Way, and now we learn there are trillions of galaxies in the Universe.
Is there life closer to home? What about in the Solar System? There are a few existing places we could look for life close to home. Really any place in the Solar System where there’s liquid water. Wherever we find water on Earth, we find life, so it make sense to search for places with liquid water in the Solar System.
I know, I know, life could take all kinds of wonderful forms. Enlightened beings of pure energy, living among us right now. Or maybe space whales on Titan that swim through lakes of ammonia. Beep boop silicon robot lifeforms that calculate the wasted potential of our lives.
Sure, we could search for those things, and we will. Later. We haven’t even got this basic problem done yet. Earth water life? Check! Other water life? No idea.
It turns out, water’s everywhere in the Solar System. In comets and asteroids, on the icy moons of Jupiter and Saturn, especially Europa or Enceladus. Or you could look for life on Mars.
Mars is similar to Earth in many ways, however, it’s smaller, has less gravity, a thinner atmosphere. And unfortunately, it’s bone dry. There are vast polar caps of water ice, but they’re frozen solid. There appears to be briny liquid water underneath the surface, and it occasionally spurts out onto the surface. Because it’s close and relatively easy to explore, it’s been the place scientists have gone looking for past or current life.
Researchers tried to answer the question with NASA’s twin Viking Landers, which touched down in 1976. The landers were both equipped with three biology experiments. The researchers weren’t kidding around, they were going to nail this question: is there life on Mars?
In the first experiment, they took soil samples from Mars, mixed in a liquid solution with organic and inorganic compounds, and then measured what chemicals were released. In a second experiment, they put Earth organic compounds into Martian soil, and saw carbon dioxide released. In the third experiment, they heated Martian soil and saw organic material come out of the soil.
Three experiments, and stuff happened in all three. Stuff! Pretty exciting, right? Unfortunately, there were equally plausible non-biological explanations for each of the results. The astrobiology community wasn’t convinced, and they still fight in brutal cage matches to this day. It was ambitious, but inconclusive. The worst kind of conclusive.
Researchers found more inconclusive evidence in 1994. Ugh, there’s that word again. They were studying a meteorite that fell in Antarctica, but came from Mars, based on gas samples taken from inside the rock.
They thought they found evidence of fossilized bacterial life inside the meteorite. But again, there were too many explanations for how the life could have gotten in there from here on Earth. Life found a way… to burrow into a rock from Mars.
NASA learned a powerful lesson from this experience. If they were going to prove life on Mars, they had to go about it carefully and conclusively, building up evidence that had no controversy.
The Spirit and Opportunity Rovers were an example of building up this case cautiously. They were sent to Mars in 2004 to find evidence of water. Not water today, but water in the ancient past. Old water Over the course of several years of exploration, both rovers turned up multiple lines of evidence there was water on the surface of Mars in the ancient past.
They found concretions, tiny pebbles containing iron-rich hematite that forms on Earth in water. They found the mineral gypsum; again, something that’s deposited by water on Earth.
NASA’s Curiosity Rover took this analysis to the next level, arriving in 2012 and searching for evidence that water was on Mars for vast periods of time; long enough for Martian life to evolve.
Once again, Curiosity found multiple lines of evidence that water acted on the surface of Mars. It found an ancient streambed near its landing site, and drilled into rock that showed the region was habitable for long periods of time.
In 2014, NASA turned the focus of its rovers from looking for evidence of water to searching for past evidence of life.
Curiosity found one of the most interesting targets: a strange strange rock formations while it was passing through an ancient riverbed on Mars. While it was examining the Gillespie Lake outcrop in Yellowknife Bay, it photographed sedimentary rock that looks very similar to deposits we see here on Earth. They’re caused by the fossilized mats of bacteria colonies that lived billions of years ago.
Not life today, but life when Mars was warmer and wetter. Still, fossilized life on Mars is better than no life at all. But there might still be life on Mars, right now, today. The best evidence is not on its surface, but in its atmosphere. Several spacecraft have detected trace amounts of methane in the Martian atmosphere.
Methane is a chemical that breaks down quickly in sunlight. If you farted on Mars, the methane from your farts would dissipate in a few hundred years. If spacecraft have detected this methane in the atmosphere, that means there’s some source replenishing those sneaky squeakers. It could be volcanic activity, but it might also be life. There could be microbes hanging on, in the last few places with liquid water, producing methane as a byproduct.
The European ExoMars orbiter just arrived at Mars, and its main job is sniff the Martian atmosphere and get to the bottom of this question.
Are there trace elements mixed in with the methane that means its volcanic in origin? Or did life create it? And if there’s life, where is it located? ExoMars should help us target a location for future study.
NASA is following up Curiosity with a twin rover designed to search for life. The Mars 2020 Rover will be a mobile astrobiology laboratory, capable of scooping up material from the surface of Mars and digesting it, scientifically speaking. It’ll search for the chemicals and structures produced by past life on Mars. It’ll also collect samples for a future sample return mission.
Even if we do discover if there’s life on Mars, it’s entirely possible that we and Martian life are actually related by a common ancestor, that split off billions of years ago. In fact, some astrobiologists think that Mars is a better place for life to have gotten started.
Not the dry husk of a Red Planet that we know today, but a much wetter, warmer version that we now know existed billions of years ago. When the surface of Mars was warm enough for liquid water to form oceans, lakes and rivers. And we now know it was like this for millions of years.
While Earth was still reeling from an early impact by the massive planet that crashed into it, forming the Moon, life on Mars could have gotten started early.
But how could we actually be related? The idea of Panspermia says that life could travel naturally from world to world in the Solar System, purely through the asteroid strikes that were regularly pounding everything in the early days.
Imagine an asteroid smashing into a world like Mars. In the lower gravity of Mars, debris from the impact could be launched into an escape trajectory, free to travel through the Solar System.
We know that bacteria can survive almost indefinitely, freeze dried, and protected from radiation within chunks of space rock. So it’s possible they could make the journey from Mars to Earth, crossing the orbit of our planet.
Even more amazingly, the meteorites that enter the Earth’s atmosphere would protect some of the bacterial inhabitants inside. As the Earth’s atmosphere is thick enough to slow down the descent of the space rocks, the tiny bacterialnauts could survive the entire journey from Mars, through space, to Earth.
If we do find life on Mars, how will we know it’s actually related to us? If Martian life has the similar DNA structure to Earth life, it’s probably related. In fact, we could probably trace the life back to determine the common ancestor, and even figure out when the tiny lifeforms make the journey.
If we do find life on Mars, which is related to us, that just means that life got around the Solar System. It doesn’t help us answer the bigger question about whether there’s life in the larger Universe. In fact, until we actually get a probe out to nearby stars, or receive signals from them, we might never know.
An even more amazing possibility is that it’s not related. That life on Mars arose completely independently. One clue that scientists will be looking for is the way the Martian life’s instructions are encoded. Here on Earth, all life follows “left-handed chirality” for the amino acid building blocks that make up DNA and RNA. But if right-handed amino acids are being used by Martian life, that would mean a completely independent origin of life.
Of course, if the life doesn’t use amino acids or DNA at all, then all bets are off. It’ll be truly alien, using a chemistry that we don’t understand at all.
There are many who believe that Mars isn’t the best place in the Solar System to search for life, that there are other places, like Europa or Enceladus, where there’s a vast amount of liquid water to be explored.
But Mars is close, it’s got a surface you can land on. We know there’s liquid water beneath the surface, and there was water there for a long time in the past. We’ve got the rovers, orbiters and landers on the planet and in the works to get to the bottom of this question. It’s an exciting time to be part of this search.
If we really want to find life on other worlds, why do we keep looking for life based on carbon and water? Why don’t we look for the stuff that’s really different?
In the immortal words of Arthur C. Clarke, “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”
I’m seeking venture capital for a Universal buffet chain, and I wondering if I need to include whatever the tentacle equivalent of forks is on my operating budget. If there isn’t any life, I’m going to need to stop watching so much science fiction and get on with helping humanity colonize space.
Currently, astrobiologists are hard at work searching for life, trying to answer this question. The SETI Institute is scanning radio signals from space, hoping to catch a message. Since humans use radio waves, maybe aliens will too. NASA is using the Curiosity Rover to search for evidence that liquid water existed on the surface of Mars long enough for life to get going. The general rule is if we find liquid water on Earth, we find life. Astronomers are preparing to study the atmospheres of extrasolar planets, looking for gasses that match what we have here on Earth.
Isn’t this just intellectually lazy? Do our scientists lack imagination? Aren’t they all supposed to watch Star Trek How do we know that life is going to look anything like the life we have on Earth? Oh, the hubris!
Who’s to say aliens will bother to communicate with radio waves, and will transcend this quaint transmission system and use beams of neutrinos instead. Or physics we haven’t even discovered yet? Perhaps they talk using microwaves and you can tell what the aliens are saying by how your face gets warmed up. And how do we know that life needs to depend on water and carbon? Why not silicon-based lifeforms, or beings which are pure energy? What about aliens that breathe pure molten boron and excrete seahorse dreams? Why don’t these scientists expand their search to include life as we don’t know it? Why are they so closed-minded?
The reality is they’re just being careful. A question this important requires good evidence. Consider the search for life on Mars. Back in the 1970s, the Viking Lander carried an experiment that would expose Martian soil to water and nutrients, and then try to detect out-gassing from microbes. The result of the experiment was inconclusive, and scientists still argue over the results today. If you’re going to answer a question like this, you want to be conclusive. Also, getting to Mars is pretty challenging to begin with. You probably don’t want to “half-axe” your science.
The current search for life is incremental and exhaustive. NASA’s Spirit and Opportunity searched for evidence that liquid water once existed on the surface of Mars. They found evidence of ancient water many times, in different locations. The fact that water once existed on the surface of Mars is established. Curiosity has extended this line of research, looking for evidence that water existed on the surface of Mars for long periods of time. Long enough that life could have thrived. Once again, the rover has turned up the evidence that scientists were hoping to see. Mars was once hospitable for life, for long periods of time. The next batch of missions will actually search for life, both on the surface of Mars and bringing back samples to Earth so we can study them here.
The search for life is slow and laborious because that’s how science works. You start with the assumption that since water is necessary for life on Earth, it makes sense to just check other water in the Solar System. It’s the low hanging fruit, then once you’ve exhausted all the easy options, you get really creative.
Scientists have gotten really creative about how and where they could search for life. Astrobiologists have considered other liquids that could be conducive for life. Instead of water, it’s possible that alternative forms of life could use liquid methane or ammonia as a solvent for its biological processes. In fact, this environment exists on the surface of Titan. But even if we did send a rover to Titan, how would we even know what to look for?
We understand how life works here, so we know what kinds of evidence to pursue. But kind of what evidence would be required to convince you there’s life as you don’t understand it? Really compelling evidence.
Go ahead and propose some alternative forms of life and how you think we’d go searching for it in the comments.
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One answer to the Fermi Paradox is the idea of the Great Filter; the possibility that something wipes out 100% of intelligent civilizations. That why we’ve never discovered any aliens… they’re all dead. Is that our future too?
In a previous episode, I presented the idea of the Fermi Paradox. If space is huge, like space huge, not aircraft carrier huge, and there are billions upon billions of stars, AND there seem to be lots of habitable planets around those stars, where are all the damn aliens?
Now, chalk up two more worlds for a famous red dwarf star in our own galactic neck of the woods. An international team of astronomers including five researchers from the Carnegie Institution announced the discovery this week of two exoplanets orbiting Kapteyn’s Star, about 13 light years distant. The discovery was made utilizing data from the HIRES spectrometer at the Keck Observatory in Hawaii, as well as the Planet Finding Spectrometer at the Magellan/Las Campanas Observatory and the European Southern Observatory’s La Silla facility, both located in Chile.
The Carnegie Institution astronomers involved in the discovery were Pamela Arriagada, Ian Thompson, Jeff Crane, Steve Shectman, and Paul Butler. The planets were discerned using radial velocity measurements, a planet-hunting technique which looks for tiny periodic changes in the motion of a star caused by the gravitational tugging of an unseen companion.
“That we can make such precise measurements of such subtle effects is a real technological marvel,” said Jeff Crane of the Carnegie Observatories.
Kapteyn’s Star (pronounced Kapt-I-ne’s Star) was discovered by Dutch astronomer Jacobus Kapteyn during a photographic survey of the southern hemisphere sky in 1898. At the time, it had the highest proper motion of any star known at over 8” arc seconds a year — Kapteyn’s Star moves the diameter of a Full Moon across the sky every 225 years — and held this distinction until the discovery of Barnard’s Star in 1916. About a third the mass of our Sun, Kapteyn’s Star is an M-type red dwarf and is the closest halo star to our own solar system. Such stars are thought to be remnants of an ancient elliptical galaxy that was shredded and subsequently absorbed by our own Milky Way galaxy early on in its history. Its high relative velocity and retrograde orbit identify Kapteyn’s Star as a member of a remnant moving group of stars, the core of which may have been the glorious Omega Centauri star cluster.
The worlds of Kapteyn’s Star are proving to be curious in their own right as well.
“We were surprised to find planets orbiting Kapteyn’s Star,” said lead author Dr. Guillem Anglada-Escude, a former Carnegie post-doc now with the Queen Mary University at London. “Previous data showed some irregular motion, so we were looking for very short period planets when the new signals showed up loud and clear.”
It’s curious that nearby stars such as Kapteyn’s, Teegarden’s and Barnard’s star, though the site of many early controversial claims of exoplanets pre-1990’s, have never joined the ranks of known worlds which currently sits at 1,794 and counting until the discoveries of Kapteyn B and C. Kapteyn’s star is the 25th closest to our own and is located in the southern constellation Pictor. And if the name sounds familiar, that’s because it made our recent list of red dwarf stars for backyard telescopes. Shining at magnitude +8.9, Kapteyn’s star is visible from latitude 40 degrees north southward.
Kapteyn B and C are both suspected to be rocky super-Earths, at a minimum mass of 4.5 and 7 times that of Earth respectively. Kapteyn B orbits its primary once every 48.6 days at 0.168 A.U.s distant (about 40% of Mercury’s distance from our Sun) and Kapteyn C orbits once every 122 days at 0.3 A.U.s distant.
This is really intriguing, as Kapteyn B sits in the habitable zone of its host star. Though cooler than our Sun, the habitable zone of a red dwarf sits much closer in than what we enjoy in our own solar system. And although such worlds may have to contend with world-sterilizing flares, recent studies suggest that atmospheric convection coupled with tidal locking may allow for liquid water to exist on such worlds inside the “snow line”.
And add to this the fact that Kapteyn’s Star is estimated to be 11.5 billion years old, compared with the age of the universe at 13.7 billion years and our own Sun at 4.6 billion years. Miserly red dwarfs measure their future life spans in the trillions of years, far older than the present age of the universe.
“Finding a stable planetary system with a potentially habitable planet orbiting one of the very nearest stars in the sky is mind blowing,” said second author and Carnegie postdoctoral researcher Pamela Arriagada. “This is one more piece of evidence that nearly all stars have planets, and that potentially habitable planets in our galaxy are as common as grains of sand on the beach.”
Of course, radial velocity measurements only give you lower mass constraints, as we don’t know the inclination of the orbits of the planets with respect to our line of sight. Still, this exciting discovery could potentially rank as the oldest habitable super-Earth yet discovered, and would make a great follow-up target for the direct imaging efforts or the TESS space telescope set to launch in 2017.
“It does make you wonder what kind of life could have evolved on those planets over such a long time,” added Dr Anglada-Escude. And certainly, the worlds of Kapteyn’s Star have had a much longer span of time for evolution to have taken hold than Earth… an exciting prospect, indeed!
-Read author Alastair Reynolds’ short science fiction piece Sad Kapteyn accompanying this week’s announcement.
During a hearing last week before the U.S. House Science and Technology Committee SETI scientists Seth Shostak and Dan Werthimer asserted that solid evidence for extraterrestrial life in our galaxy — or, at the very least, solid evidence for a definitive lack of it — will come within the next two decades. It’s a bold claim for scientists to make on public record, but one that Shostak has made many times before (and he’s not particularly off-schedule either.) And with SETI’s Allen Telescope Array (ATA) continually scanning the sky for any signals that appear intentional, exoplanets being discovered en masse, and new technology on deck that can further investigate a select few of their (hopefully) Earth-like atmospheres, the chances that alien life — if it’s out there — will be found are getting better and better each year.
Would you put your bet on E.T. being out there? Actually, you can.
Thanks to the internet and the apparently incorrigible human need to compete you can actually place a wager on when alien life will be discovered, via an Irish online betting site.
Typically focused on the results of international sporting matches, PaddyPower.com has also included the announcement of extraterrestrial life in its novelty bet section, hinging on “the sitting President of the USA making a statement confirming without doubt the existence of alternative life beings from another planet.” The odds of such an announcement being made in the years 2015-2018 are currently listed at 100 to one. After that they drop significantly… probably because by then the JWST will be in operation and we will “have the technology.”
Of course, whether you personally would place a wager on such things is purely personal preference, and neither I nor Universe Today condones or supports gambling, for aliens or otherwise. (And the legalities of doing so and any and all results thereof are the sole responsibility of the reader.) But it is interesting that we now live in a time when wagering on the discovery of alien life sits just a click away from the results of the Kentucky Derby, French Open, or World Cup.
Now if you really want to support the science that will make such a discovery possible — maybe even within our own Solar System — you can “stand up for space” and write your representatives to tell them you want NASA’s planetary science budget to be funded, and rather than gamble your money you can make a donation to support SETI’s ongoing mission here (or even help out yourself via [email protected].)
And even if all else fails, you could end up with a free coffee courtesy of Dr. Shostak…