The Life in the Cosmos evening panel discussion in San Diego, held in conjunction with the SPIE Optics + Photonics symposium in late August, provided a glimpse into the complexities of looking for life forms from the far reaches of space.
Moderators Paul Davies and Richard Hoover presided over a distinguished panel of experts who talked about their research, each concept shedding some light on how traces of life might be discovered:
- Paul Davies of the University of Arizona suggested that exploding a three to five-megaton bomb on the surface of Mars would excavate the subsurface water aquifers. A feature roughly the size of Meteor Crater in Arizona would finally expose the subsurface Martian biota and settle the life on Mars question. Contamination, he said, would be a non-issue because of the already high radiation background on Mars. With robotic observers on hand to watch the explosion and analyze the ejecta, this would be the "home run" experiment.
- Richard Hoover of NASA described his work with unusual microorganisms on Earth that thrive in hostile conditions. Growing at temperatures >100C, producing enzymes to locally dissolve ice, and eating sugars or sulfur are all tactics employed by earth organisms to survive. Coupled with recent evidence for cyanobacteria in ancient carbonaceous chondrites, Hoover believes that this provides a solid basis to extend what we consider the earth's biosphere into the local cosmos.
- Gilbert Levin of Spherix Inc. and PI for the Viking experiment to find life on Mars continues his advocacy for the presence of life on the surface of the planet. There have been no experiments to find life on Mars since the Viking lander in the 1970s, due in part to the dominant interpretation of the Viking results as inconclusive to negative. Gil says that the return of samples from Mars is essential to further this research, along with applying new instrumentation to the Viking-tested experimental method.
- Eric Galimov, from the Vernadsky Institute in Russia, talked about a proposed 2009 sample-return mission to Phobos, which would help determine whether Phobos is truly part of Martian geology. Current evidence indicates that Phobos is a C type asteroid that could also host organics or bacteria.
- Michael Storrie-Lombardi of the Kinohi Institute emphasized the role that viruses play in the evolution of single-celled life. Some gene transfer is mediated by viruses and genes can even be transferred between different organisms by this method. In order to understand the conditions for life in the early solar system, we need a better understanding of how viruses interact with the rest of the biosphere, he says. Unfortunately, we may be losing one of the best laboratories for the paleobiology necessary for this understanding as Antarctica begins to undergo non-linear global warming events.
- Victor Gallardo of the Unversity of Concepcion in Chile, discussed his studies of anaerobic "shallow shelf macrobacteria," which grow from several microns to several millimeters in length. Vast bacterial mats cover large parts of the Chilean coastal ocean, producing an enormous biomass in nearly anaerobic conditions.
- Dirk Schulze-Makuch of Washington State University highlighted the likely sites for life in our solar system - Venus, Mars, and Titan - and speculated that carbon-based life is most likely to be found. Alternative biochemistry based on hydrogen peroxide is highly unlikely due to the need for a stabilizer, while silicon is not reactive enough.
- Chandra Wickramasinghe of Cardiff University (UK) said that interstellar bacteria could survive for more than a million years. He discussed the theory of "panspermia," the distribution of life throughout the universe by genes or spores and the possibility that life on earth originated via bombardment of the earth by dust and solar nebular ices.
Panelists also discussed the problem of finding and communicating with extra-terrestrials. They acknowledged that the public is captivated by the question of whether we are alone in the universe, rather than whether bacteria can live somewhere besides Earth. "Microbe hunters" (astrobiologists) approach the search in much different ways than the intelligence hunters who run SETI. For years, scientists have been looking for messages planted in electromagnetic radiation. Paul Davies suggests that another mode of communication would be to put the message in viruses which are then sent them out into the universe. These viruses insert genomic "junk DNA" into other organisms. Not all DNA mutates as rapidly as others and some extant fragments are 40 million years old. A stable message, such as "if you can read this, call home," could be inserted into the genomes of simple organisms and still be readable today.