Raman spectroscopy of volcanic lavas and inclusions of relevance to astrobiological exploration

Abstract

Volcanic eruptions and lava flows comprise one of the most highly stressed terrestrial environments for the survival of biological organisms; the destruction of botanical and biological colonies by molten lava, pyroclastic flows, lahars, poisonous gas emissions and the deposition of highly toxic materials from fumaroles is the normal expectation from such events. However, the role of lichens and cyanobacteria in the earlier colonization of volcanic lava outcrops has now been recognized. In this paper, we build upon earlier Raman spectroscopic studies on extremophilic colonies in old lava flows to assess the potential of finding evidence of biological colonization in more recent lava deposits that would inform, first, the new colonization of these rocks and also provide evidence for the relict presence of biological colonies that existed before the volcanism occurred and were engulfed by the lava. In this research, samples were collected from a recent expedition to the active volcano at Kilauea, Hawaii, which comprises very recent lava flows, active fumaroles and volcanic rocks that had broken through to the ocean and had engulfed a coral reef. The Raman spectra indicated that biological and geobiological signatures could be identified in the presence of geological matrices, which is encouraging for the planned exploration of Mars, where it is believed that there is evidence of an active volcanism that perhaps could have preserved traces of biological activity that once existed on the planet’s surface, especially in sites near the old Martian oceans.