Surface-enhanced Raman micro-spectroscopy of DNA/RNA bases adsorbed on pyroxene rocks as a test of in situ search for life traces on Mars

SERS spectroscopy with 785-nm laser excitation minimizing fluorescence emission is exploited for remote analysis of life traces in an extraterrestrial environment. Adenine and guanine, nucleobases present in both DNA and RNA strands, and microRNA containing adenine and guanine have been used as testing ligands for identifying traces of nucleic acids in Martian rocks and sediments. SERS spectra of these nucleobase samples adsorbed on pyroxene substrates have been investigated with micro-Raman apparatus in the absence of sample manipulation and inducing the signal enhancement by deposition of silver colloidal nanoparticles over the pyroxene/nucleobase substrates. An order-of-magnitude estimate of the sample amount responsible for the SERS spectra is given. Copyright (C) 2009 John Wiley & Sons, Ltd.