Are we alone in this universe, this is a popular question mankind struggling to answer throughout the history. But still we could not find exact answer yet. From the start of space exploration, we are trying to find possibilities of life in our solar system and outside universe. According to current data there is no any possibility of intelligent life in our solar system. but there is some possibility of primary life in some places in solar system like Jupiter or Saturn moons. Also there is a possibility of life in some outside solar systems recently found.
Scientists believe, to form a life there should be following ingredients.
- Liquid water
- Energy source
- Biological elements
There are few places in our solar system which contains some of above ingredients.
Mars having huge interest on finding life. But still there is no any good evidence to support. Due to its habitable zone and similarities to earth there are lot of investigations to find life on mars via telescopes and remote probes. There are lot of evidence shows mars had liquid water in past. Up to date scientists believed there is no liquid water in mars. But recent discovery found there can be a subsurface lake in mars. Currently primary objective of mars exploration is finding traces of past life.
Europa is a one of the four major moons of Jupiter.it is covered with ice layer. Scientists believe there is a subsurface ocean exists below the surface ice cap. In that case there may be environment for life. Because of this Europa is identified as one of the major locations in solar system for life. There are many science fictions talking about life in Europa including space odysy by Arther c clerk
Titan is the largest moon of Saturn. Which is having lakes and revers of Methane. And also, thick atmosphere with carbon compounds. Scientists believe this environment is good for start of life. If life exists on Titan it may completely different than earth life because those life is based on liquid methane, but earth it is liquid water.
Enceladus is a moon of Saturn which is covered by ice. According to observations of Casini space craft there are some geyser like water vapor jets in polar region. Scientists believe there can be liquid ocean under the ice cap of moon and it can support some sort of life.
Venus is the second planet of solar system. For the long time it is believe that there is no possibility of life due to it is extreme conditions. With high temperature and pressure the surface of planet cannot support life. But recent study suggest there can be some sort of life exists in higher atmosphere. If there is a life in Venus those can be most probably consist of floating microbes.
Other places which there is a small possibility of life are
- Ganymede and Callisto Jupiter moons
- Triton Moon of Neptune
- Mimas Saturn moon
Scientists now continue searching for life in other solar systems. Finding planets in habitable zones of stars.
NASA mission using Kepler telescope helped to find thousands of exoplanets. Most of them are in habitable zone. Even though those exoplanets are found the distance to those planets become it is difficult to explore them. For example, nearest exoplanet is Proxima Centauri b which is in 4 light year away. With currant technology travel this distance will take centuries.
Limitations in Extraterrestrial life
Astrophysicist Frank Drake has developed formula to calculate number of alien civilizations in our galaxy which can communicate with us. According to it there are more than 10,000 civilizations in this galaxy. But it is problematic that still we did not come across any sign of other civilization.
Number of projects attempt to find any radio wave telecast from other civilizations including SETI. Decades of search not found any trace up to date.
Some scientists believe earth is the only home for life. According to them Life is a very rare incident in this universe. Fermi paradox is popular theory in this philosophy. Which is developed by physicist Enrico Fermi, according to this theory even though there are some intelligent life in universe but meeting them is impossible due to life of universe and distance between those planets and earth. Those intelligent civilizations may already destroyed before us. Or they may have already visited the earth before us. According to Firmi paradox there may be some filters which prevent intelligent life to become advance civilization. For humans we may already passed this Great filter or it is ahead of us. In both cases there is lesser possibility of meeting with other civilizations. Because if it is ahead of us means we will destroy before that. If we have already passed it means other civilizations may destroyed already.
Also there is a possibility that alien life exists but we are not able to recognize. The life as we know is based on carbon. The carbon-based life in our planet is evolved during 4 billions of years. We cannot expect it will happen same way in other planets. There may be some sort of life in universe which is not recognizable to our senses or even the tools developed by us.
Even In earth there are life found some extreme conditions which we believe no life can support.
When we look into night sky, we see millions of stars. Same way other aliens from one of those stars also may looking and asking the same question as us. That is the nature of universe, we may miss our cosmic friends by time and distance.