When I was a student in the 1960s, anyone who speculated about life beyond Earth was considered a crackpot. Today, astrobiology is flourishing. It is a key component in the mission statements of NASA and the European Space Agency. All this despite the fact that we still do not have a shred of direct evidence that there is any life at all beyond our planet.
So what has changed? One factor is the discovery that life on Earth can survive in a much wider range of environments than scientists used to believe possible. There are microbes that thrive near scalding…
