I find several of Lewis's ideas plausible as answers for some
common science-religion interaction questions, although occasional there is
an obvious scientific problem.
In Out of the Silent Planet, Malacandra has death but not sin as a result
of attack by Satan in the distant past. This is a possible explanation of
the presence of predation, disease, death, etc. in animals before the
appearance of humans on Earth.
The series provides a partial answer to the question of "what does it mean
for Christianity if there are aliens?". His essay The Seeing Eye (in a
couple of collections including a small paperback entitled The Seeing Eye
as well as the large collection Christian Reflections) gives a more
detailed treatment of the question, in part inspired by noticing that, at
different times, people have claimed that either an absence of aliens or
presence of aliens is a problem for Christianity. He concludes that there
is no impact on the truth of Christianity, but there may be impact on the
organization of missionary activity.