The Church does not have a specific teaching on
extra-terrestrial life. The subject, however, is tied up with the
whole question of biological evolution, about which the Church has
shown great reserve (cf. Pope Pius XII, Humani
generis). Can life come about by
chance processes at work in the natural physical and chemical
operation of the universe? If this can occur on earth, then
presumably it can occur elsewhere, given the right conditions. This
much can be said affirmatively, all rational embodied creatures (those with a body
and a soul), wherever they are in the universe, have Christ as their
Head and Redeemer (Col. 1:15-20). If intelligent life exists
elsewhere, then it has a relationship
with the Incarnation and Redemption.
However, despite all the glib claims by
agnostic scientists that intelligent life must exist
somewhere else among the billions and billions of galaxies, the best
models and mathematical analyses show the probably of an earth-like
environment anywhere in the universe to be practically zero.
The fact that there is life on Earth, therefore, is an anomaly that
came about by design, not chance. Cosmologists call it the Anthropic
(man) Principle, in order to get away from filling the holes in the
scientific models with God. As persons and believers they may do so,
in their role as scientists they may not.
So, if intelligent life exists somewhere
else, it will be by design, as well. And, that life will be
incorporated into God's plan, as St. Paul certainly declares of
everything that IS. Personally, I think we are IT (pun intended), and there is
nothing in scientific discoveries to dissuade me from that opinion.
But if such life should be discovered, it would fit into
God's Plan in some way.
The Holy Father has stated that we should not
argue from science to what we believe. Physics does not exist to
prove Genesis, for example. However, the witness of science to the
realities to which faith also testifies is increasingly evident.
Over time the way in which science and faith can be reconciled
becomes clearer. Since all truth has God as its author, it is
exactly what we would expect to occur.
An evangelical physicist by the name of Dr.
Hugh Ross has sought to reconcile contemporary science and faith. He
shows how the discoveries in astronomy support the existence of a
Designer and how discoveries in biology and other fields do not
support evolutionary biology. While a Catholic would not always
agree with his theological positions, the scientific analysis of his
team of believing scientists is superb. With that caveat I can
recommend his books on the scientific questions.