The quest for exoplanets is the greatest scientific adventure of the XXIst Century.
It involves astronomers and biologists.

It's a mind odyssey, started more than 2,000 years ago by greek philosophers, which is being achieved today. The search for exoplanet is the search for the "Others", our hypothetic cousins on "Terrae Incognitae".
It's the serarch for life, but then, there's a catch:
What exactly IS LIFE?
After all, looking for Earth's twins, isn't it a new geocentrism?
Life depends on the observer: like in painting, it's the spectator who makes the picture, life is not in things, but in our relationship with things.
Life is not an essence, but a relationship.
IOW, there is no life strictu senso, but only SIGNS OF LIFE.

The problem is, we try to define life without even knowing what it is, and this makes the search even more difficult. What we use to define life can also be applied to cristals, to Earth, to galaxies.
And what if we found signs of life on an exoplanet, 50 light-years away? What do we do? We use our imagination because we're going to be faced with a technological wall. We won't be able to know what it looks like. Exoplanets are too far away and it will be perhaps as long as this quest took up to know, before we can even reach them.

OK, well, it was roughly translated from the magazine "Science et Vie" which I'm currently reading.