Saturday, September 5, 2015

Where Are We Most Likely To Find Extraterrestrial Life?

10 Places Most Likely To Harbour Alien Life




    Perhaps we’re super-curious, or perhaps we’re just desperate to find that we’re not alone in the universe, but there are a great many scientists out there dedicating their lives and careers to finding the most likely homes for extraterrestrial life.
    Obviously it would be great if one of our big, fancy space telescopes suddenly sent back a picture of an Earth-like planet lit up like a Christmas tree with a big “We Are Here” sign stuck in the top of it, but unfortunately that hasn’t happened yet, so scientists have to be a little more cunning.
    In the search of alien life, it’s all about probabilities. We are 100% sure that life has formed on at least one planet in the universe, so it makes the most sense to go looking for alien worlds that closely resemble our own. 
    However, the cosmos might not have such an absolute idea of what life in the universe should look like, so we need to be open to the possibilities of extra-terrestrials looking nothing like anything we’ve ever seen before.
    So where are we looking? The simple answer is everywhere, with our telescopes scanning the whole sky for a peep of alien life. Obviously, it’s easier to get a closer look at the planets in our own solar systems, but with the discovery of a huge number of Earth-like exoplanets over the last couple of decades, our options are becoming seemingly endless.


      10. Io



      Io, the third largest moon orbiting Jupiter, seems like an unlikely choice for the cradle of life, due to the 400+ active volcanoes on its surface, wildly variable surface temperatures and deadly ionized gasses swirling about its atmosphere. Io orbits Jupiter in a band of radiation called the Io plasma torus that would quickly kill anything on its surface.
      However, some scientists believe that Io wasn’t always the vision of hell that it is today, and that the early Io might have had plenty of liquid water on its surface that has since all been evaporated by the violent volcanic activity. 
      It is thought that these ancient lakes could have been a nursery for life that has since retreated below the moon’s troubled surface, clinging to life in the underground lava tubes and sustained by the energy given off by the volcanic activity.
      Unfortunately, even if Io is home to a race of alien mole people, we’re unlikely to find them any time soon as it would require a large-scale mining operation that we simply don’t have technology or funding for at the moment. Due to the aforementioned hellish surface, we can’t exactly expect them to poke their heads out either.
      If we were to discover even the simplest organic life on Io, it would stand us in pretty good stead for discovering it elsewhere as, if life can survive the radioactive oven of Io, it can survive anywhere.



        9. Kepler-186f



        The snappily named Kepler-186f was the first validated Earth-like exoplanet found to be orbiting its star in the habitable “Goldilocks” zone.
        Kepler-186f is thought to be no more that 10% bigger than Earth and probably has a rocky surface just like our home planet. It orbits its star, Kepler-186, at the outer edge of the habitable zone but with a much faster year-length of 130 days compared to our 365. 
        Good news for night owls as it would be a bit darker there as the star that it orbits is roughly half the size and mass of our sun, with the midday sun at roughly the same brightness on Kepler-186f as it is an hour before sunset on Earth.
        In our search for alien life, scientists start by searching for planets that are as similar to Earth as possible.This isn’t just narrow-mindedness, but just playing the probabilities. 
        We already know that Earth-like conditions can produce complex and even intelligent life, so it makes for a very good place to start in our search for extra terrestrials. If we just launched straight in looking for life in the form of sulphur-metabolising clouds of intelligent gas, then we wouldn’t know the first thing about where to start looking or how to spot it when we find it.


          8. Enceladus



          Enceladus is a tiny moon orbiting Saturn, barely the width of Arizona, but it has gotten astrobiologists all of a flutter recently due to one crucial element: Water.
          Huge plumes of water vapour erupt from the moon’s surface, misting out into space before falling back to the surface and beginning the cycle again. One of the great things about these plumes is that we don’t have to land on Enceladus’ surface to get a good idea of the kinds of materials that are present there. When the Cassini space probe flew through one of these plumes, it was able to detect the presence of organic molecules such as nitrogen, carbon and oxygen – all of which are required for life.
          The speed at which these plumes are shot out of the moon’s surface suggests that they originate from an underground ocean or reservoir, and the pressure required to fire out a plume of water at over 650 mph suggests some kind of geological activity that is responsible for melting water ice and firing it into space.

          The presence of water in liquid and vapour form implies the existence of a water cycle, like the one here on Earth, that could easily circulate organic molecules and increasing the likelihood that, over time, they would form the building blocks of microbial life.

            7. Europa


            Over the years, many missions to discover the secrets of our solar system have thrown up some interesting findings about Europa, one of Jupiter’s many moons.
            The moon’s surface appears to be made up of solid ice, but it is almost unnaturally smooth. As most bodies in the solar system are pockmarked with impact craters, Europa’s youthful appearance suggests that it is being continually renewed, in turn suggesting high levels of geological activity. 
            The mysterious surface is also marked by great lines called linea which crisscross its surface. By tracking these linea, we have observed that they are slowly but surely moving across the surface, evidence of potential tectonic or volcanic activity beneath the icy crust. 
            If this is indeed the case, then the ocean beneath the moon’s surface could be home to the kind of life-forms that flourish around volcanic hydrothermal vents in the deepest oceans here on Earth.
            Like Enceladus, Europa appears to be ejecting huge jets of water through holes in its surface, this means that future missions could fly through them and collect samples to analyse for the markers of life.


              6. Asteroids/Meteorites



              The search for life in the universe is not just limited to planets and moons and there have been over 22,000 meteorite discoveries over the years that are thought to have the potential to harbour life.
              This isn’t to say that there is a little race of meteor people building houses on their rocky hosts, but there is evidence to suggest that many meteors contain the organic compounds needed to form the building blocks of life.
              If this is true then it lends credence to the astrobiological theory of “panspermia” (literally meaning “seeds everywhere”). This theory hypothesises that life on Earth was seeded by the organic compounds delivered by meteor impacts during the formation of the solar system, as well as the delivery of water in the form of icy meteors.
              In 1996, scientists thought that they had spotted evidence of “microfossils” on a Martian meteor, perhaps showing that life could have existed on or around the red planet around 3.6 million years ago. The discovery has been the subject of fierce debate and scientists have still been unable to come up with a conclusive decision in the years since the discovery.



                5. Venus


                Venus is perhaps a slightly surprising candidate in the search for alien life. Despite the fact that it is one of our closest neighbours in the solar system, and in some ways very similar to our planet Earth, the surface of Venus remains something of a mystery to us due to its impenetrably thick atmosphere.
                It is generally thought that due to the searing temperatures of over 450°C and the choking sulphurous atmosphere, the surface of Venus would be dead and sterile. However, more recently, astrobiologists have begun to consider the possibility of life existing in the slightly cooler upper atmosphere.
                Here on Earth we have a belt of microbes and insects constantly in orbit in the upper reaches of our atmosphere so it’s not actually that wild of an idea that something similar could occur on a planet with an atmosphere as thick as Venus’s.
                As well as this, the composition of the Venusian atmosphere might actually indicate the presence of organic life. There are certain molecules there such as sulfur dioxide (SO2) and hydrogen sulfide (H2S) that shouldn’t really occur together unless something is producing them, something organic.
                All of this put together makes it conceivable that the clouds of Venus could indeed be an unlikely ark for life in the universe.


                  4. Gliese 667 Cc


                  Despite the fact that  Gliese 667 Cc is located in the habitable zone of its host star, life on the surface would be very different to life on Earth.
                  The star that it orbits is actually a red dwarf and most of the light that reaches the planet’s surface is in the infrared part of the spectrum. This would mean that if anything there managed to evolve anything like eyes, they would be more adapted to detecting this part of the electromagnetic spectrum. Light visible to us would plunge the surface of the planet into a perpetual twilight.
                  It is also possible that, due to the planet’s proximity to its host star, it would be tidally locked, much like our moon is to the Earth. This means that one side of the planet would be constantly facing the sun and bathed in eternal daylight, whereas the other side would be covered in permanent darkness.
                  Most extraordinarily of all, the star Gliese 667 C is part of a triple star system. These would not appear quite so huge in the skies of  Gliese 667 Cc, but they would be very prominent. It would also be possible to see our own sun as a distant star as it is only 22 light-years away from us.
                  Life would be tough for anything living on the surface of Gliese 667 Cc due to the likelihood of regular solar flares from its red dwarf host, bathing the planet in radiation. We do know of lifeforms here on Earth that are capable of withstanding these kinds of conditions, however, such as the virtually unkillable Tardigrade or “waterbear”, so it is perfectly possible that these kinds of organism could have evolved on a world such as  Gliese 667 Cc.


                    3. Titan


                    Titan – Saturn’s largest moon – might be a good candidate for life due to the fact that it has a thick, chemically active atmosphere, liquid lakes and a relatively Earth-like weather system.
                    As far as we know, life requires some shielding from the solar radiation of outer space, much like our atmosphere, and Titan’s thick atmosphere would afford such protection to any life on its surface.
                    The only issue we have with Titan is that, despite its lovely thick atmosphere, the chemical make up of this atmosphere is very different to our own. This, and the fact that the moon is much colder than the Earth, is the reason why Titan was disregarded for a long time as a potential candidate for extraterrestrial life, but some scientitst think that we may have been too quick to reject it.
                    The surface temperature of Titan is around -179°C, far too cold for liquid water to be present, but it does have large lakes of liquid methane and ethane that are saturated with hydrocarbons – i.e. the building blocks of life.
                    If we did find that Titan harbours life, it would completely rewrite what we know about the conditions under which life can form. If life were to exist on Titan, it would differ from life on Earth in some subtly different ways, probably breathing in hydrogen instead of oxygen and exhaling methane instead of carbon dioxide. It might also burn acetylene for energy instead of glucose like we do.
                    There has been some talk flying around of sending a lander probe to go and take a closer look at Titan, but so far nothing has been confirmed.

                      2. Mars


                      Due to the fact that, relatively speaking, Mars is just right next door, we have managed to find out more about this planet than any others in the solar system.
                      Although, so far, we haven’t spied any alien civilisations waving back at us through our telescopes, scientists think that Mars displays evidence that it could once have been home to alien life.
                      Today, Mars is far too cold for liquid water to exist on its surface and its atmosphere is far too thin to be able to protect any potential life from the radiation of outer space. The red planet does have water ice on its surface, but it is locked up in the soil and the polar ice caps, rendering it unusable.
                      However, it is is thought that many years ago, Mars would have been a much nicer, much more Earth-like place to be. There is evidence to suggest that it once had a magnetic field that would have enabled it to maintain a thicker atmosphere, thus protecting it from solar radiation and trapping heat, allowing rivers and lakes of liquid water to run over its surface. 
                      These rivers and lakes could well have been home to ancient microbial life forms, before the strong solar wind blew the atmosphere right off of Mars, leaving it the cold and barren place it is today.
                      Even though it is unlikely that we’ll discover life on Mars today, if we can confirm that it did at least once harbour alien life forms, it will prove once and for all that Earth is not the only place in the universe where living organisms can develop, essentially doubling the number of planets that we know to be or have been habitable.

                        1. Kepler-452b


                        One of the most recently discovered entries on our list, Kepler-452b caused quite the stir in July of 2015 when it was excitedly dubbed “Earth 2.0”.
                        The exoplanet, orbiting the star known as Kepler-452, is 60% larger than the Earth and scientists think that it is likely to have a rocky surface similar to Earth. It orbits the sun-like star in the much-sought-after Goldilocks zone, it’s year is about the same length as a year on Earth, surface temperatures and conditions are likely to be similar and it is, for all intents and purposes, just like Earth’s bigger, slightly older cousin.
                        The reason why scientists have been getting so excited about Kepler-452b is that it has spent roughly six million years in that Goldilocks Zone sweet spot, more than enough time for life, perhaps even intelligent life, to have evolved on its surface.
                        Even if we find that, for whatever reason, complex life hasn’t managed to take hold on Kepler-452b, some scientists think it might still make quite a cosy home for space-faring humans in the distant future. That’s if we can manage to cross the 1,400 light-years of open space between us and the planet’s surface.
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