We are searching for biosignatures that could indicate whether life exists on other planets. In particular, we are pursuing the hypothesis that some lipids may be uniquely generated by living systems and could be reliable indicators of life on other planets. To test this idea, we are collecting samples from lava tube environments on earth that are similar to lava tubes on Mars, which we think are particularly suitable to harbor life. We are evaluating the types of lipids found in these lava tube samples, and whether they can serve as reliable biosignatures.