Conference summary: life detection in extraterrestrial samples.

In February 2012, a conference was convened at the Scripps Institution of Oceanography in La Jolla, California, on the subject of life detection in extraterrestrial samples (program and abstracts available at http://www.lpi.usra.edu/meetings/ lifedetection2012). The aim of the conference was to explore the kinds of tools, methods, and approaches necessary for detecting evidence of life in extraterrestrial samples, including those that arrive on Earth by natural processes and those that are deliberately returned by engineered missions. Samples that might be returned from Mars by a future mission were a primary topic of interest. Presentations and discussions at the conference drew upon diverse fields of research, including meteorite studies, modern and ancient terrestrial analog studies, studies of samples returned by past lunar and comet sample return missions, studies of modern traces of life on Earth, and studies of the facilities needed to conduct this kind of research. The conference program was organized with extensive discussion sessions. This report summarizes the results of the conference. The topic of life detection was examined from two different but partially overlapping perspectives: the ‘‘science perspective’’ arising from the desire to know whether life ever arose on Mars and the ‘‘planetary protection perspective’’ arising from the need to protect our own planet from contamination by any potentially harmful living extraterrestrial organisms that may be contained in returned samples. The former relates to detection of any kind of evidence of either ancient or present-day life, whereas the latter is concerned with evidence of present-day viable organisms. A review of the topic of life detection is timely given the scope of recent advances in life-detection studies on Earth, the publication of the National Research Council’s Planetary Science Decadal Survey (which identified seeking the signs of life via Mars sample return (MSR) as its highest priority in the flagship class of missions; National Research Council, 2011), as well as the strategic emphasis within both NASA and ESA on life detection. One of the primary approaches to life detection is via the study of extraterrestrial samples, although other astrobiological approaches also exist. In the case of a potential MSR campaign, significant forward planning is required to ensure best possible practices are implemented throughout the campaign (iMARS Working Group, 2008; MEPAG E2E-iSAG, 2012): from the design and operation of a sample collection rover to containment and preservation of samples in transit, and appropriate handling and analysis of the samples after they have returned to Earth. The array of planned or possible life-detection strategies and measurements has implications for virtually every aspect of a sample return campaign. Thus, it is critical to understand these strategies and measurements well in advance to avoid compromising the fundamental scientific objectives and planetary protection requirements of an MSR campaign. Much of the discussion summarized below assumed MSR would be a robotic endeavor. However, the mission may ultimately involve humans rather than robots. In that case, some aspects of laboratory analyses and sample handling may need to be reassessed. The conference was also an introduction to a subsequent planetary protection workshop dealing specifically with the planetary protection test protocol.