The search for extraterrestrial habitable planets will require long observation times and the intelligent selection of appropriate parent stars and target biosignatures. While life can certainly develop in the absence of photosynthesis, such life forms on earth exhibit metabolic rates several orders of magnitude less than the activity accompanying a photosynthetic-driven ecosystem. The most accessible spectral biosignatures are those accompanying a system driven away from thermodynamic equilibrium by photosynthetic activity. For example, the co-existence in a planetary atmosphere of significant amounts of ozone, oxygen, and methane would be a strong indication of biotic activity. Investigating the issue of the Habitable Zone from the standpoint of the constraints inherent in photosynthesis it appears that the absorption characteristics of photosynthetic microorganisms on this planet make it likely that photosynthetic activity can exist on planets orbiting stars to red-ward of the Sun on the H-R diagram. Such a possibility is encouraging for terrestrial planet finder efforts since stars classified red-ward of our sun (G3 to K7) account for more than 55% of our nearest neighbors.

Molecular biology techniques have enabled us to prepare and select RNA aptamers that can bind specifically to small targets. RNA oligonucleotides can also be used as fluorescent probes. We have combined the two approaches to obtain Aptamer Beacons, in which molecular recognition is linked to the emission of an optical signal. These RNA biosensors could be used to detect directly the signatures of life in samples of mineral and extra-terrestrial material.

Central to understanding the origin of life is the elucidation of the first replication mechanism. The RNA World hypothesis suggests that the first self-replicating molecules were RNAs and that DNA later superceded RNA as the genetic material. RNA viruses were not subjected to the same evolutionary pressures as cellular organisms; consequently, they likely possess remnants of earlier replication strategies. Our laboratory investigates how members of the RNA virus family Bromoviridae can have structurally distinct 3' end tags yet are specifically recognized by conserved replication enzymes. This work addresses the idea that 3' tRNA tails were functionally replaced in some viruses by an RNA-protein complex. These viruses may serve as a timeline for the transition from the RNA world to DNA and protein based life.

Although on Mars no near-surface life has been detected, some preservation of organics with depth is expected. Stratigraphic and geochemical information on low-organic carbon (50% samples with Total Organic Carbon = 0.05 − 0.12%) Fe-oxides/oxyhydroxide-rich horizons of deeply buried red paleosoils (late Paleocene-early Eocene(?) in age) are presented here. They were retrieved during the Ocean Drilling Program (ODP) Leg 197 (Emperor Seamounts, North Pacific Transect). Organic traces in Hole 1205A are likely to reflect a complex history of paleosoil formation. Materials from an extremely deep (sub-basement) diagenetic setting, i.e., 46.8 to 309.9 meters below seafloor (mbsf), could represent a model for possible deep subsurface soils preserved on Mars.

We recognize the theoretical objections and strong assumptions in bioastronomy against the feasibility of non-carbon based life (NCBL). Yet, we make a long-term commitment to testing these assumptions by parameterization of a wide range of NCBL characteristics using General Morphology, direct lab tests of giant planet gasses and energy sources at extreme temperatures and pressures for spontaneous NCBL subunit formation, and development of a range of instruments for lab and remote sensing of putative NCBL complex macromolecules.

At the level of individual protein sequences, humans are 97–100% identical to the great apes, our closest evolutionary relatives. The evolution of humans (and of human intelligence) from a common ancestor with the chimpanzee and bonobo involved many steps, influenced by interactions amongst factors of genetic, developmental, ecological, microbial, climatic, behavioral, cultural and social origin. The genetic factors can be approached by direct comparisons of human and great ape genomes, genes and gene products, and by elucidating biochemical and biological consequences of any differences found. We have discovered multiple genetic and biochemical differences between humans and great apes, particularly with respect to a family of cell surface molecules called sialic acids, as well as in the metabolism of thyroid hormones. The hormone differences have potential consequences for human brain development. The differences in sialic acid biology have multiple implications for the human condition, ranging from susceptibility or resistance to microbial pathogens, effects on endogenous receptors in the immune system, and potential effects on placental signaling, expression of oncofetal antigens in cancers, consequences of dietary intake of animal foods, and development of the mammalian brain.

Science requires objectivity - the ability to see the relationships among things in the natural world free of assumptions and biases. To achieve this goal one has to use objective methods of observation and testing but also maintain a philosophy of objectivity when deciding upon which research questions to pursue and which conclusions to draw from one's findings. The field of bioastronomy relies upon objectivity on both a methodological level and, perhaps to the greatest extent among all sciences, on a conceptual level. Bioastronomy is the multidisciplinary and interdisciplinary science of investigating, understanding, and explaining the origin, nature, prevalence, and distribution of life in the universe. As a scientific field of inquiry bioastronomy relies upon methodological objectivity. Furthermore, bioastronomy demands conceptual objectivity because its content domain is, by nature, largely unknown and subject to more degrees of freedom than perhaps any other discipline. Therefore, objectivity, through and through, is the cornerstone of bioastronomy.

The timing of emergence of major organismal groups is consistent with the climatic temperature being equal to their upper temperature limit of growth (Tmax), implying a temperature constraint on the evolution of each group, with the climatic temperature inferred from the oxygen isotope record of marine cherts. Support for this constraint comes from the correlation of Tmax with the rRNA molecular phylogenetic distance from the last common ancestor (LCA) for both thermophilic Archaea and Bacteria. In particular, this correlation for hyperthermophilic Archaea suggests a climatic temperature of about 120°C at the time of the LCA, likely in the Hadean.

The extent to which organisms can survive extended periods of metabolic inactivity in cold environments such as permafrost is one of the key questions in the study of life in extreme environments and for astrobiology. Viable bacteria have been cultured from million year-old Siberian permafrost samples, but the relationship between the age of the bacteria and the age of the sediments remains controversial. In this study we analyze the level of racemization of amino acids in permafrost samples collected from several sites in Northern Siberia. We have shown that even during long exposures to low temperatures (−10°C to −15°C), the bacterial cells in permafrost are not completely dormant, but continue to metabolize and at least partially control the extent of amino acid racemization.

Theory and direct observation indicate that micro-organisms exist in liquid veins in ice and permafrost, provided the temperature is above the eutectic for H2O and soluble impurities present. Microbes can exist and metabolize in glacial ice and permafrost on Earth, Mars, and Europa. One can search directly (with fluorescence microscopy at liquid veins in Vostok ice core samples) or with a biologging instrument (for microbial fluorescence in a borehole in terrestrial or martian permafrost or ice). The viability lifetime against DNA destruction of bacterial spores can be measured with analytical techniques that identify calcium dipicolinate, which is unique to spores.

Vital clues on life's origins within the galaxy exist here on present day Earth. Life is currently divided into the three domains Bacteria, Archaea and Eukarya based on the phylogeny of small ribosomal subunit RNA (16S/18S) gene sequences. The domains are presumed to share a “last universal common ancestor” (LUCA). Hyperthermophilic bacteria and archaea, which are able to thrive at 80°C or higher, dominate the bottom of the tree of life and are thus suggested to be the least evolved, or most “ancient”. Geochemical data indicates that life first appeared on Earth approximately 3.8 billion years ago in a hot environment. Due to these considerations, hyperthermophiles represent the most appropriate microorganisms to investigate the origins of metabolism. The central biochemical pathway of gluconeogenesis/glycolysis (the Embden-Meyerhof pathway) which produces six carbon sugars from three carbon compounds is present in all organisms and can provide important hints concerning the early development of metabolism. Significantly, there are a number of striking deviations from the textbook canonical reaction sequence that are found, particularly in hyperthermophilic archaea. In this paper the phylogenetic istribution of enzymes of the pathway is detailed; overall, the distribution pattern provides strong evidence for the pathway to have developed from the bottom-up.

Paralana is an active, radon-containing hot spring situated in a region of South Australia's Flinders Ranges with a long history of hydrothermal activity. Gas bubbling into the pool is composed of radon (from the radioactive decay of radium), nitrogen, carbon dioxide, and trace helium and hydrogen. The microbial composition of mat and biofilm samples from Paralana was determined using culture-independent 16S rRNA techniques. We have previously demonstrated that the hot spring contains a diverse bacterial community. Here we summarise these findings and report on the Archaea identified in Paralana. Archaeal inhabitants include members of the Crenarchaeota and Euryarchaeota kingdoms.

To better understand constraints on bacteria at extremely low temperatures in ice, we describe here the adaptation of methods previously developed for sea ice to high magnification imaging of bacteria within fluid inclusions of Arctic lake ice under insitu conditions. Bacterial staining procedures, using the DNA-specific fluorescent stain DAPI, epifluorescence microscopy and image analysis were applied to lake-ice sections at in situ temperature (-5°C). Abundances of total, attached, free-living and metabolically active lake-ice bacteria were also determined from samples melted at 0°C using the fluorescent stains DAPI and CTC. Initial results indicate that, compared to sea ice at the same in situ temperature, lake ice contains fewer and more isolated liquid inclusions, limiting transport of fluids and motion of bacteria. Metabolically active cells were found in all ice samples (0.1 to 2.0% of the total counts), but on average less than in sea ice. Up to 50% of the total bacterial community were found to be associated with particles > 3 μm in size; of the metabolically active cells, a smaller fraction may be attached than in sea ice. Our results expand the spectrum of information available on bacteria in ice on a scale relevant to the organism and provide insight into characteristics of frozen microbial habitats on Earth and perhaps elsewhere in the Universe.

Due to the hostile conditions at the surface, any life forms existing on Mars today would most likely inhabit a subsurface environment where conditions are potentially wetter and warmer, but organic compounds may be lacking and light energy for photosynthesis would be absent. Methanogens, members of the domain Archaea, are microorganisms from planet Earth that can grow under these relatively extreme conditions. We have demonstrated that certain methanogenic species can indeed grow on a Mars soil simulant, JSC Mars-1, with limited amounts of water, under conditions approaching a possible subsurface environment on Mars.

To date, no SETI observing program has succeeded in detecting any unambiguous evidence of an extraterrestrial technology. Regrettably, this paper will therefore not dazzle you with the analysis of the contents of any interstellar messages. However, as is appropriate for a plenary presentation, this paper does provide an update on the state of SETI programs worldwide. It discusses the various “flavors” of observational SETI projects currently on the air, plans for future instrumentation, recent attempts to proactively plan for success, and the prospects for future public/private partnerships to fund these efforts. The paper concludes with some tentative responses to the “What if everybody is listening, and nobody is transmitting?” query.

In optical SETI (OSETI) experiments, it is generally assumed that signals will be deliberate, narrowly targeted beacons sent by extraterrestrial societies to large numbers of candidate star systems. If this is so, then it may be unrealistic to expect a high duty cycle for the received signal. Ergo, an advantage accrues to any OSETI scheme that realistically suggests where and when to search. In this paper, we elaborate a proposal (Castellano, Doyle, & McIntosh 2000) for selecting regions of sky for intensive optical SETI monitoring based on characteristics of our solar system that would be visible at great distance. This can enormously lessen the amount of sky that needs to be searched. In addition, this is an attractive approach for the transmitting society because it both increases the chances of reception and provides a large reduction in energy required. with good astrometric information, the transmitter need be no more powerful than an automobile tail light.

Optical SETI at Lick Observatory is characterized by its robust approach to initial detections. Our three-detector system has distinguished itself by successful rejection of nearly all false positive signals. We present observational progress, discuss use of data analysis procedures such as FFTs and analysis of double coincidences, and mention plans to upgrade our instrumentation.

The SETI@home project has recently completed its third year of active data analysis. Over 4 million volunteers have joined the search, providing a combined total of over 1 million CPU-years of processing power. SETI@home performs a sensitive search for extraterrestrial signals in a 2.5 MHz band centered on 1420 MHz. SETI@home searches a wide parameter space including 14 octaves of signal bandwidth and 15 octaves of pulse period with Doppler drift corrections from −50 Hz/s to +50 Hz/s. We will briefly describe the SETI@home project and the algorithms used in the SETI@home client. We will describe the post-processing methods we use to reject RFI and select candidate signals from the nearly 4 billion “hits” returned by SETI@home clients.

We have conducted a direct Search for Extraterrestrial Intelligence at the Water Maser frequency, 22.235 GHz, using the Very Large Array. The targets were 13 solar-type stars that were known to host exoplanetary systems. In all cases, the RMS limits of the flux density, 20 mJy (5σ), were sufficient to rule out any omnidirectional transmitters of the same power as terrestrial radars (5 × 1012 W). We discuss the significance of this non-detection.

We describe the ongoing high and ultrahigh-resolution survey of OH masers in the southern hemisphere. The study is made using one of the 30-m antennas of the Argentine Institute for Radioastronomy (IAR) connected simultaneously to two different spectrometers: (a) one 1008 channel correlator with a spectral resolution of 33 to 312 Hz, and (b) an eight million channel analyzer with a spectral resolution of 0.05 Hz (META II). The observations are performed with a high-gain feed with 35K system temperature. The preliminary survey is concentrated within a list of 24 strong OH masers at 1665 and 1667 MHz. The purpose of our research is to test theoretical considerations about the mechanisms of temporal variation in OH masers as well as the possible use of OH masers as natural amplifiers of extraterrestrial artificial signals.