Life on Earth...Life Elsewhere?Life as we know it on earth requires a certain environment to survive. Even so, there are creatures on earth which seem to be able to survive in harsh environments, where the temperatures are very cold, or where there is little water or oxygen. It is environments like these which are similar to those found on other planets.
Sophisticated life forms are relative newcomers on Earth compared to bacteria or archaea. They arrived later because the Earth proved to be a healthy environment over a long period of time. Because the environment of other planets is more primitive, life on other planets (if it exists) may be primitive and unsophisticated. If not, life would have developed the ability to withstand otherworldly environments as well as finding material for nutriment. We might have to imagine what such creatures would be like.
Non-sophisticated life forms may have an easier time in a harsh environment. Even so, all life as we know it, leave behind certain signs that it has been there. In 1996, scientists mistakenly thought that they had discovered life on Mars. But, there has not been any concrete evidence as of yet of life anywhere in the solar system besides Earth.