Just as we have been curious about how life originated on the Earth, we have also tried to explore whether there is life on any other planet in the Solar System or elsewhere in the universe. Explorations of outer space carried out by spacecraft and ground based observatories, in recent years, have led us to the conclusion that in the entire Solar System, the planet Earth is, perhaps, the only place where there is life. The other planets are at such a distance from the Sun that they are either too hot or too cold for life toexist. The one close possibility is the planet Mars. Space probe Viking collected and analysed samples of rock and soil from Mars to detect the presence of life. But so far no conclusive evidence of any life, present or past, has been found on this planet. Man is also looking for life beyond the Solar System. Two approaches are currently available to him; either to send a man or an instrument to a particular star in the Universe and examine local surface for life or to listen to the signals from outer space which may come in the form of radio waves. With our present technology, the first approach does not take us beyond the Solar System.
The second approach is based on the assumption that there may be civilisations technically as advanced or even more advanced than our own. So we can exchange radio messages with them. We have drawn a blank so far on this front. But it is quite possible that our galaxy, the entire system of dust, gases, and stars within which the Sun moves, is already filled with chatter between the far older and more advanced civilisations! These signals may havc been transmitted b) a technique still undiscovered on Earth, so we may be nlissi!?g them altogether! Recently it has been reported that astronomers have found sornc other stars, like our Sun, which have planets. If this is provcd to be true, there may bc millions of planetary systems in the Universe, increasing the likelihood of lifc cxisting on some of them.