Our knowledge of life is based on a single example: life on Earth. This constrains our understanding of what life is, and what life can be. It would expand our knowledge to be able to travel to other planets and observe the completely independent instances of life that occur there.
If we were to observe life on other planets, it would most likely be carbon based, and therefore would likely share much in common with life on Earth. The opinions of evolutionary biologists vary widely on how similar such independent instance of organic life might be, and unfortunately, we will probably never know the truth.
Opinions also vary widely about the plausibility of life based on media other than carbon chemistry. But certainly to be able to observe non-carbon based life would expand our concepts of life even more than the observation of carbon based life on other planets. Non-carbon based life would be even more alien than merely extra-terrestrial life.
The relatively new field of ``Artificial Life'' (AL) explores the possibilities of creating independent instances of life, or elements of the life process. AL is about understanding life by building it rather than by taking it apart. It is a synthetic rather than a reductionist or analytic approach.
AL can bear the same relation to biology, that synthetic chemistry bears to chemistry. If the field of chemistry were restricted to the study of naturally occurring chemicals on Earth, it would never have achieved either the theoretical strength or practical benefits that it enjoys today. Biology stands to gain much from expanding biological studies beyond life forms that occur naturally on Earth.