If you go back around a hundred years in time you’ll find that speculation about extraterrestrial life was rampant, much like today. However, in 2017, our expectations of finding life in the solar system are much more measured than they were for our ancestors. No more theories of lakes on Mars dug by the Martian race or Dinosaurs walking on a balmy Venus.
Seth Shostak, a senior astronomer at the SETI Institute, which is currently on the lookout for alien signals coming from the depths of space, has run through the most likely places we will find simple microbial life in our solar system; the list includes places we’re already exploring but also other places we’ve only taken photos of, on flyby missions.
First on the list, is Mars. The red planet is the most extensively searched place that features on the list, we’ve sent crafts to orbit the planet, we’ve landed rovers to learn more about the terrain of the planet and now we are preparing to land people on the surface. Shostak believes there could be life forms hidden under the dusty surface of Mars, about 30 meters down or below, where some liquid water may also be present.
Next up we have three of the four Galilean moons that orbit around Jupiter, the largest planet in the solar system. Io is a fiery volcano planet so it’s not considered to be particularly hospitable to life, however, the remaining three, Europa, Callisto, and Ganymede have potential. According to Shostak, Europa’s subsurface oceans could host life which might survive using the hotspots at the bottom of the oceans which are like “little mini volcanoes and that would give you energy for life.” Both Ganymede and Callisto also host oceans but Europa remains the most likely place for life.
The next location is Saturn, where two of its moons, Titan and Enceladus, could potentially harbor life. Although less well known than Europa, Enceladus is one of the most likely places where life could be found and it turns out that it’s not so hard to find out either. Shostak said “it’s shooting geysers into space. So you don’t have to land. You don’t have to drill. You just go grab some of [that] geyser gunk and bring it back to Earth and maybe you’ll find aliens.” Titan, on the other hand, has liquid lakes of natural gas, so it could also sustain life.
The final candidate that Shostak put forward was Pluto. We’ve only just got decent pictures of the dwarf planet thanks to a flyby. Shostak hypothesizes that there are pockets of liquid water underneath the surface of Pluto which means it could also host microbial life.
When asked whether we’ll find extraterrestrial intelligent life, Shostak replied that it might be found in the next two decades. “There’s a lot of real estate out there, right? There are a trillion planets in the Milky Way. We can see a trillion other galaxies, each with a trillion planets. If they’re not out there, then all these people behind us are really special.”
It may seem impossible to discover extraterrestrial intelligent life in the next 20 years, but considering the leaps that human technology has made over just the past two decades, it could be possible, or perhaps it's just a hopeful bias.