The development of civilizations such as ours into spacefaring, multi-planet entities requires significant raw materials to construct vehicles and habitats. Interplanetary debris, including asteroids and comets, may provide such a source of raw materials. In this article, we present the hypothesis that extraterrestrial intelligences (ETIs) engaged in asteroid mining may be detectable from Earth. Considering the detected disc of debris around Vega as a template, we explore the observational signatures of targeted asteroid mining (TAM), such as unexplained deficits in chemical species, changes in the size distribution of debris and other thermal signatures that may be detectable in the spectral energy distribution (SED) of a debris disc. We find that individual observational signatures of asteroid mining can be explained by natural phenomena, and as such they cannot provide conclusive detections of ETIs. But, it may be the case that several signatures appearing in the same system will prove harder to model without extraterrestrial involvement. Therefore, signatures of TAM are not detections of ETI in their own right, but as part of ‘piggy-back’ studies carried out in tandem with conventional debris disc research, they could provide a means of identifying unusual candidate systems for further study using other search for extra terrestrial intelligence (SETI) techniques.

Synthetic geomicrobiology is a potentially new branch of synthetic biology that seeks to achieve improvements in microbe–mineral interactions for practical applications. In this paper, laboratory and field data are provided on three geomicrobiology challenges in space: (1) soil formation from extraterrestrial regolith by biological rock weathering and/or the use of regolith as life support system feedstock, (2) biological extraction of economically important elements from rocks (biomining) and (3) biological solidification of surfaces and dust control on other planetary surfaces. The use of synthetic or engineered organisms in these three applications is discussed. These three examples are used to extract general common principles that might be applied to the design of organisms used in synthetic geomicrobiology.

We investigate the possibility of habitable Trojan planets in the HD 23079 star–planet system. This system consists of a solar-type star and a Jupiter-type planet, which orbits the star near the outer edge of the stellar habitable zone in an orbit of low eccentricity. We find that in agreement with previous studies Earth-mass habitable Trojan planets are possible in this system, although the success of staying within the zone of habitability is significantly affected by the orbital parameters of the giant planet and by the initial condition of the theoretical Earth-mass planet. In one of our simulations, the Earth-mass planet is captured by the giant planet and thus becomes a habitable moon.

Laboratory experiments were conducted to determine the effect of descent-engine plumes on the scouring of surface (microbial) contaminants from a spacecraft. A simulated touchdown of a half-scale lander engine and deck configuration was conducted at Mars atmospheric pressure in the NASA Ames Planetary Aeolian Laboratory. Low-density particles were used for the soil simulant to emulate the lower Martian gravity. The underside of the model had small witness plates with controlled microbial surface populations and particle impact detectors. For both steady-state engine thrust (Viking) and pulsed engine thrust (Phoenix), the exhaust plumes from the engines violently excavated the soil and produced particle-laden eddies beneath the lander that sandblasted the lander underside. The result was nearly complete erosion of microbial contaminants from the spacecraft model with their subsequent deposition in the surrounding area. It is concluded that different planetary protection cleanliness levels for different parts of a spacecraft do not necessarily prevent soil contamination because these cleaning strategies evolved without consideration of the effects of the descent engine plumes.

The Zoo Hypothesis posits that we have not detected extraterrestrial intelligences (ETIs) because they deliberately prevent us from detecting them. While a valid solution to Fermi's Paradox, it is not particularly amenable to rigorous scientific analysis, as it implicitly assumes a great deal about the sociological structure of a plurality of civilizations. Any attempt to assess its worth must begin with its most basic assumption – that ETIs share a uniformity of motive in shielding Earth from extraterrestrial contact. This motive is often presumed to be generated by the influence of the first civilization to arrive in the Galaxy. I show that recent work on inter-arrival time analysis, while necessary, is insufficient to assess the validity of the Zoo Hypothesis (and its related variants). The finite speed of light prevents an early civilization from exerting immediate cultural influence over a later civilization if they are sufficiently distant. I show that if civilization arrival times and spatial locations are completely uncorrelated, this strictly prevents the establishment of total hegemony throughout the Galaxy. I finish by presenting similar results derived from more realistic Monte Carlo Realization (MCR) simulations (where arrival time and spatial locations are partially correlated). These also show that total hegemony is typically broken, even when the total population of civilizations remains low. The Zoo Hypothesis is therefore only justifiable on weak anthropic grounds, as it demands total hegemony established by a long-lived early civilization, which is a low probability event. In the terminology of previous studies of solutions to Fermi's Paradox, this confirms the Zoo Hypothesis as a ‘soft’ solution. However, an important question to be resolved by future work is the extent to which many separate hegemonies are established, and to what extent this affects the Zoo Hypothesis.

Carbonate rocks in the Mojave Desert are presented as potential analogues for the carbonates on Mars. Rocks collected from the Little Red Hill site contain iron oxide-bearing coatings that greatly suppress the spectral features due to carbonate of the underlying material and impart a spectral slope. The Mojave Desert was formerly a lush pedogenic soil environment that, over time, transformed into the current arid climate with abundant rock varnish. One niche for microbes in the current desolate environment is inside and underneath the rocks where the microbes profit from solar protection by the iron oxide rock coatings. Carbonates were long predicted to be present on Mars and have recently been detected by instruments on Phoenix and MER and using hyperspectral orbiters such as the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), the Planetary Fourier Spectrometer (PFS) and the Thermal Emission Spectrometer (TES). We describe here the results of a study of carbonate rocks from the Little Red Hill site of the Mojave Desert that includes X-ray diffraction (XRD), chemistry and visible-infrared reflectance spectroscopy. Coatings on the carbonate rocks greatly reduced the strength of the carbonate bands and caused changes in the shape of some bands. We compare these data with a carbonate outcrop at Nili Fossae, Mars. If microbes once inhabited Mars, similar carbonate rocks with iron oxide coatings could have provided a UV-protected niche there as well. Thus, analysis of carbonate-bearing regions on Mars by future landers would be useful sites to search for biosignatures.

Long space flights and planetary settlement will require sources of nutrition and chemicals that must be generated in space. This will include not only amino acids and vitamins but also oxygen, all of which can be generated by means of biosynthesis. Synthetic biology has the potential to generate organisms designed for supplying human nutritional needs in space. Photosynthetic microbes may be ideal for this purpose, as they are more efficient per volume cultivated than green plants at conversion of light to chemical energy, biomass and nutritional molecules. In addition, microbes are easier and faster to genetically engineer, facilitating not only design and terrestrial manufacture of organisms optimized for growth and nutrient production in the artificial conditions of space, but superior ability in space to develop organisms suited to newly discovered environments. The rapid ability to adapt and create new microbes to suit new circumstances when in space offers significant potential for risk reduction. Development of sun-driven microbial production of nutritional chemicals would also have terrestrial benefits in commerce and sustainability. A synthetic biology approach to chemical production would not be based on fossil fuels as such fuels do not exist on other planets. This approach would highlight a synergistic relationship between outer space and ‘spaceship earth’, illustrating NASA's role in stimulating technology development with terrestrial application. Two specific approaches deserve consideration: production by traditional photosynthetic microbes, or by the newly appreciated capacity of some bacteria to absorb electric current (e.g. solar panels) to drive metabolism. Palatability and sensory stimulation are a key part of food consumption and could be engineered into microbes. As a first step, NASA should test a bioreactor in which genetically engineered, nutrient-producing photosynthetic bacteria are grown and harvested in space.