When We're Looking for Life on Other Planets, What Exactly Are We Looking For?

June 27, 2013
When We're Looking for Life on Other Planets, What Exactly Are We Looking For?

Is there life on other planets?

To answer that question, you first have to answer this one: what, exactly, is life? We may have a general sense of life as it exists here on Earth -- one that involves a given object's ability to metabolize and grow, to respond to stimuli, to maintain homeostasis, to reproduce. But that textbook definition of life -- "life," that is, "as we know it" -- is itself entirely defined by the particularities of Earth. It's a set of criteria determined by a planet that happens to be terrestrial, that happens to be covered in salt water, that happens to orbit a yellow dwarf star ... and that happens to be shielded from said star by a protective ozone layer.

Life as we know it, in other words, is entirely contingent on its environment. As the Harvard astronomy professor Dimitar Sasselov puts it: "We have life here on Earth that has its roots in the chemistry of the planet."

Read the full Atlantic Article.

See also: 2013