Searching for Aliens from our backyard
Copernicus by removing earth from the centre of the Universe and by placing it in the orbit around an ordinary star our Sun (and consequently later astronomers placing that star one among hundreds of billions in an ordinary galaxy in an a universe that has hundreds of billions of galaxies) has made the biggest revolution in the history of natural philosophy. Darwinian evolution has dethroned humans from special creation and showed us to be a ‘beast’ like any other species originating in the African savanna whose fossils anthropologists discover all the time. Now we sit lonely at the 3rd rock from the sun and think that are we the only thinking and sapient being in the heartbreakingly large universe that started about 13.8 billions years ago? Are there other sapient aliens thinking the same sitting at a waterhole of a planet orbiting some far away star?
For many years SETI project has been trying to eve’s dropping radio messages sent by extraterrestrial intelligent civilisations. But till date there is absolute radio silence, what our radio telescope natural humming and hiss emitted by ionised hydrogen recapturing their lone electrons, not a SOS by galactic hitchhiker or a love letter by an alien to his GF to a galaxy far far away. There are three possibilities. One technologically advanced ET is absent or very rare or there is protocol not to disturb or interfere with backward species like us so they are hiding their messages in disguise of natural radio signals. Second, their communication technology uses some exotic science yet to be discovered by us. Third possibility is that no technologically advanced Intelligent ET has yet evolved in our backyard of the galaxy.
Our galaxy is a large place, if a star goes supernova on the other side of the galaxy. Its light will reach us only after about 80 thousand years. Suppose, if there is a technologically advanced civilization evolved at the other side of our galaxy. a lakh years back, their automated reconnaissance mission has landed on a continent that we call Africa. Mission has found a species of apes that has just invented fire making. A Report was sent using a radio transmitter, that there is a species of ape evolving there has potential for becoming technologically advanced species. It is only now they must have received the report and if they have sent the typical handshake message ‘Hello Earthlings’ ! We will get this message in the year 102023 AD!
Another approach that is popular among astrobiologists is to first look for signs of basic life in the universe. This bottom up quest for life in the universe has led to success in the last few decades. First it started with searching for planets orbiting around other stars. Kepler and other missions have found about 6140 planets in 4527 planetary systems. 85% of these planets are too close to their stars to have life because they are tidally locked to their ‘Sun’ like our moon is to earth. Such planets will have one side burnt out and other permanently frozen. About one in five Sun-like stars have an earth size planet in the habitable zone. Assuming there are 400 billion stars in the Milky Way. It means there are 22 billion Earth-like habitable planets out there. Soon the James Webb space telescope is not only to discover more such planets, it will be able to find atmospheric composition of such planets.
Mercury and Venus were found to be inhospitable to life due to harsh conditions found on these inner planets. Mars initially showed lots of promise as a abode of microbial life. Initially in the history of the solar system, Mars may have been suitable for life in the past as it had liquid water and still possessed lots of frozen water in polar regions and maybe a lot at other places. Lack of an earth-like strong global magnetic field brings hard radiation of solar storms to its surface and additionally Martian surface is made sterile by UV radiation. But there are many icy moons of Jupiter and Saturn which hold a substantial subsurface ocean. Ganymede, Callisto , Europa of Jupiter and Titan and Enceladus of Saturn are such moons that hold the potential of supporting microbial life. Source of energy in such hypothetical ocean worlds would not be the Sun but partial tidal melting of these Moon by their host planets. Organic compounds that are precursors to life have been found on some of these moons.
In the coming decades many missions are planned by NASA and the European Space Agency to be sent to these moons to find aliens in our backyards.
Europa Clipper : Europa Clipper going to explore Europa, investigate its habitability and aid in the selection of a landing site for the future Europa Lander. This exploration is focused on understanding the three main requirements for life: liquid water, chemistry, and energy.
Europa Lander: to be launched 2027 to complement Europa clipper mission. The objectives of the mission are to search for biosignatures at the subsurface ≈10 cm, to characterise the composition of non-ice near-subsurface material, and determine the proximity of liquid water and recently erupted material near the lander’s location.
Dragonfly mission to Titan: A robotic rotorcraft mission to the Largest Moon of Saturn with atmosphere thicker than the Earth. It will be launched in 2028. It will study the prebiotic atmosphere of the Titan quite similar to the Earth before the origin of life.
Future Astrobiology mission concepts under consideration to water worlds in the outer Solar System:
Enceladus Explorer (EnEx)
Enceladus Life Finder (ELF)
Enceladus Life Signatures and Habitability (ELSAH)
Explorer of Enceladus and Titan (E2T)
Journey to Enceladus and Titan (JET)
Jupiter Icy Moons Explorer (JUICE)
Life Investigation For Enceladus (LIFE)
Neptune Odyssey
Titan Lake In-situ Sampling Propelled Explorer (TALISE)
Titan Mare Explorer (TiME)
Trident for Triton
