The Wikipedia describes exobiology, or astrobiology, as an interdisciplinary field, combining aspects of astronomy, biology and geology, which is focused primarily on the study of the origin, distribution and evolution of life. Astrobiology comes from the Greek words astron = star, bios = life and logos = word/science), while exobiology combines the Greek exo (=out) with biology. It is also known as xenobiology (Greek: xenos = foreign).
Some researchers make a distinction between astrobiology and exobiology, where exobiology would be more specific than astrobiology and cover only the search for life beyond Earth, as well as the effects of extraterrestrial environments on living things. (In other words, exobiology would only deal with the off-planet aspects of astrobiology). Similarly, xenobiology is now often used as that part of astrobiology that focuses on biology based on foreign chemistry, whether of extraterrestrial or terrestrial (possibly synthetic) origin.
Some major astrobiological research topics include:
-What is life?
-How did life arise on Earth?
-What kind of environments can life tolerate?
-How can we determine if life exists on other planets?
-How often can we expect to find complex life?
-What will life consist of (DNA/Carbon based? Physiology?) on other planets?
Exobiology and xenobiology are terms also found in science fiction, although typically such terms refer to the speculative biology of an extraterrestrial. A xenobiologist is usually a human doctor or biologist who is expert on the physiology of alien organisms and life forms.