We don’t yet know how life evolved on Earth, but there are theories that it started with the most basic of microbes. Despite our lack of knowledge as to what happened on Earth, we are fascinated with discovering new life in our solar system. There may, however, be a great irony in this quest that has so far failed to find life.
There is no absolute way of ensuring that the spacecraft we send up are free from Earth’s bacteria. Certain microbes have been shown to survive in the vacuum of space despite all care being taken to create sterile conditions while creating the craft. There are already thousands of pieces of man-made debris floating about space. So as to avoid further pollution and interplanetary contamination, the Cassini probe was recently allowed to burn up in the atmosphere of Saturn.
The irony may be that in seeking out life, all that mankind has done is sow the future seeds of life beyond Earth in the form of microbes. Like the bur that gets caught in animal fur or feathers, or seeds that are ingested, we are, in effect, simply dispersing the seeds of life into space. Who knows what might then develop given time? Seeking out life, may ultimately turn out to be a self-fulfilling quest.