NEO Targets for Biological In Situ Resource Utilization
Abstract:We are investigating a mission architecture concept for low-cost pre-processing of materials on long synodic period asteroids using bioengineered microbes delivered by small spacecraft.
Space exploration opportunities, particularly those requiring a human presence, are sharply constrained by the high cost of launching resources such as fuel, construction materials, oxygen, water, and foodstuffs. Near-Earth asteroids (NEAs) have been proposed for supporting a human space presence. However, the combination of high initial investment requirements, delayed potential return, and uncertainty in resource payoff currently prevents their effective utilization.
Biomining is the process in which microorganisms perform useful material reduction, sequestration or separation. It is commonly used in terrestrial copper extraction. Compared to physical and chemical methods of extraction it is slow, but very low cost, thus rendering economical even very poor ores. These advantages are potentially extensible to asteroid in situ resource utilization (ISRU).
One of the first limiting factors for the use of biology in these environments is temperature. A survey of NEA data was conducted to identify those NEAs whose projected interior temperatures remained within both potential (-5 - 100 ºC) and preferred (15 - 45 ºC) ranges for the minimum projected time per synodic period without exceeding 100 ºC at any point. Approximately 2800 of the 11000 NEAs (25%) are predicted to remain within the potential range for at least 90 days, and 120 (1%) in the preferred range.
A second major factor is water availability and stability. We have evaluated a design for a small-spacecraft-based injector which forces low-temperature fluid into the NEA interior, creating potentially habitable microniches. The fluid contains microbes genetically engineered to accelerate the degradation rates of a desired fraction of the native resources, allowing for more efficient material extraction upon a subsequent encounter.