Why is it so hard to believe that we are not alone in this universe? Are we such a competent and near perfect race that we may claim to be the only ones flourishing on a small planet in a mammoth universe.
I don't think so.
According to some, a habitable planet must
1. Have a habitable star, which provides enough light and warmth among other things.
2. Maintain a distance from that star and follows a constant circular orbit for many years.
3. Surface water should be in liquid form not frozen.
4. Maintain a safe distance from other planets such that at no time do they cross orbits.
5. Have an atmosphere of essential gases like oxygen and nitrogen.
6. Must not be massive or too small, but of a medium bulk.
These are only some conditions necessary for life on a planet. However, these conditions may not be a requisite for other life forms on other planets in other universes.
According to Hindu mythology, during a conversation of Lord Krishna (the Vishnu incarnate) with Indra, Krishna speaks of the existence of multiple universes each of which has life on it. The simultaneous existences of these universes are unknown to each other.
We are constantly on the search for discovering life beyond the frontiers of our world. Scientists once found fossils of one-celled organisms in the crevices of meteors thought to be from Mars. Therefore, the conclusion derived is that life once existed on planet Mars. This theory is disputed by many other scientists because the evidence of the fossils may have an explanation that has nothing whatsoever to do with life.
In 1961, Frank Drake, a US radio astronomer developed an equation to estimate the number of planets hosting intelligent life forms in the galaxy. His estimate was found to be 10,000.
In 1976, Viking Mars Landers discovered evidence of chemical processes on Mars, similar to that on Earth. Evolutionists suggest that life arises from non-life by purely chemical processes.
In 1977, an Ohio State University radio telescope detected an unusual pulse radiation from space. When the direction of the radiation was observed, it seemed to have come from a star more than 200 million light years away. Perhaps it was a result of an astronomical event or a transmission from intelligent species.
Jupiter's moon Europa has reddish tinge to its surface that is indicative of the presence of alien microbes.
In 2002, Russian astrobiologists discovered that Deinococcus radiourans (bacteria), which if constantly exposed to radiation can evolve and thus survive on Mars.
These evidences offer no definite proof for extra-terrestrial life. However, the search is still on, sooner or later our first definite knowledge of life on outer space will come our way.