India, Sept. 17 -- For years, the search for extraterrestrial life inside our solar system has always concentrated on the "red" planet Mars. That is because Mars is similar in size to Earth. There is now clear evidence that there was once water on its surface and most importantly, like Earth, it is also in the so-called "habitable" zone, close enough to its star for enough radiation but not so much that life wouldn't take off. Mars is, therefore, considered to either have life or to have once harboured life and capable of supporting a human expedition. As a result, we are constantly sending probes to Mars and even to its tiny moons. Probes that circle the planet as well as robotic vehicles that have roamed its surface. We actually have a ...