One more point.
I venture that, in the not-too-distant future, astronomers will make
more detections of biosignatures in our solar system and in solar
systems beyond. As the next generation of ground- and space-based
telescopes come online, their immense sensitivity, combined with the
ever-growing number of confirmed exoplanets, will likely unleash many
exciting hints of life.
But consider: Venus is our celestial neighbor, accessible by robotic
spacecraft and easily observed by telescopes. We largely know what it’s
made of, what its surface looks like, and how its atmosphere behaves.
Yet so much remains unexplained in light of this extraordinary new
finding. At least a decade will pass before any dedicated robotic
mission will arrive at Venus that could help address this question. But
at least a robotic mission is a possibility.
The detection of a biosignature in the atmosphere of a distant
exoplanet may forever remain ambiguous. It may be hundreds, if not
thousands of light-years away; far too distant for direct exploration in
our lifetime or for many human lifetimes to come. How little will we
know about its surface, geology, and climate? How could we possibly
discern or constrain the possible types of natural processes that could
result in a false signal? Or, conversely, how could we assuredly confirm
a biological origin knowing next to nothing about the context from
which it arose?
We may find clever solutions to these problems in time. But it’s very
likely they will lag behind the discoveries themselves. In that interim, we
will find ourselves in a state of excited uncertainty—the very state we
find ourselves in right now, with Venus. In the midst of ambiguity, easy
answers are seductive, even soothing. But they are likely wrong, or at
least incomplete. We must learn to embrace the uncertainty and to resist
our desires for a binary answer—life or no life?—while the process of
science does its work.