Figure 2 (IMAGE) Tokyo Institute of Technology Caption Bacteria and other living things are composed of a complex set of chemicals. As alien life may be fundamentally different from Earth-life, it may be difficult for future space probes to tell if complex chemical mixtures are derived from living or non-living processes. Credit Josef Reischig Usage Restrictions The image may only be used with appropriate caption and credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.