How to find life on exoplanets

Abstract

In this chapter we will concentrate on the detection of life based on complex carbon compounds and liquid water (i.e. on carbon—liquid water life). We thus concentrate on life that resembles that on Earth. But we are not assuming that alien life is based on the same carbon compounds as terrestrial life. It might use a carbon compound other than DNA to carry genetic information, and it might use carbon compounds other than proteins to carry out the various functions performed by proteins in terrestrial life. But it would still be carbon—liquid water life. Only in Chapter 13 will we be free of this restriction, where, in the search for extraterrestrial intelligence (SETI) we are searching for function, for evidence of technological civilisation, regardless of the chemical basis of the life forms.