Nor do they know whether life could arise in the brief time allotted.

"Russia does not seem to hesitate to make their life more difficult whenever the opportunity arises."

Did we even understand why life arose here at all?

All his life he'd avoided the question by making sure the situation never arose.

The one thing we know for certain is that life has arisen once, here on this very planet.

I said that the answer depends upon whether life has arisen only once, or many times.

And yet, so far, we've only found three worlds on which life has arisen.

One of the reasons for interest in the early atmosphere and ocean is that they form the conditions under which life first arose.

Given a few billion years, life might have arisen.

Then,' he added, 'just recently life arose on the planet.