Our goal is to develop the science strategy and engineering systems for a flight instrument to detect biochemical evidence of extraterrestrial life. This project directly addresses a core problem in Astrobiology. The search for life is a key goal of NASA’s Solar System exploration program, but currently no instruments can unambiguously recognize signatures of life. The Viking landers (1976) attempted to find life on Mars through measuring metabolic activity but this approach was flawed because relatively few microbes will grow under artificial conditions, and because conditions on the modern Mars surface are inhospitable to life. Other approaches to find life, such as searching for morphological features or isotopic signatures, are very ambiguous and require additional supporting evidence. Biochemical compounds (i.e. organic compounds of biological origin, such as DNA) are the most definitive signatures of life, provide stand-alone, unambiguous evidence, and can be used to find both extant and extinct life.
Searching for biochemical signatures of life on Mars is challenging for several reasons. First, detection requires extraction of the organic compounds from a solid matrix (soil or rock). This is a major, unresolved issue of organic detection in extraterrestrial samples. Second, most instruments that detect organic compounds can’t distinguish non-biological organics from biogenic ones. Third, biochemical signatures of life are unstable, and as a result they are often present at very low concentrations. A technique is needed that can extract and detect biochemical evidence of life, both fossil and extant, with high sensitivity and specificity.
The standard method for searching for organic compounds on Mars is pyrolysis mass spectrometry (PMS) as used on missions Viking, Phoenix, and currently by the Curiosity rover. PMS has failed to detect organic compounds on Mars probably due to the chemistry of the regolith, which destroys organic compounds during pyrolysis, before they can be identified by the MS.
The current state of the art in life detection is the Signs of Life Detector (SOLID), a TRL-5 instrument that can uniquely identify biochemical signatures of life. SOLID was developed at Centro de Astrobiologia (CAB), Madrid, Spain (PI Victor Parro). It uses an antibody microarray chip to search for up to 500 compounds simultaneously. Organic compounds are first extracted in a Sample Processing Unit (SPU) by mixing particulate samples with a buffer solution and sonicating. The extracted solution then moves to the Sample Analysis Unit (SAU) where it is analyzed using standard antibody-antigen reactions. Reactions on the microarray activate fluorescent labels that are revealed by imaging. The intensity of each well is proportional to the concentration of the target compound in the sample analyzed. The sensitivity to target compounds is up to 1-2 ppb.
Our proposed research has both scientific and technical objectives. The science goal is to identify the most important compounds to incorporate into SOLID to search for evidence of life on Mars. Recent and planned NASA missions are focused on identifying habitable environments on early Mars then searching for signatures of fossil life. We will build a library of biochemical compounds likely to be preserved as a fossil record of life. Recent Mars missions have provided evidence that Mars hosts environments that are habitable for modern life (1, 2). We will test SOLID’s performance on a diversity of analog materials including those from very low biomass Mars analogs such as the Atacama desert and dry valleys Antarctica. To support design of the SPU, laboratory studies will be performed to determine the best approach for efficiently extracting and separating organic compounds from soil or rock cuttings prior to analysis. SOLID currently uses sonication but we have developed a subcritical water extraction system that may prove more efficient for extracting compounds of interest, or a system incorporating both these features may be best.
The engineering goal is to design the sample processing part of the SOLID instrument to a fidelity sufficient to allow estimating the cost to build a flight system. Partner institution CAB has invited us to team with them on future SOLID development, taking responsibility for the SPU. They will provide the current design information. The engineering steps to accomplish the new design include: 1) analyze the existing design, 2) perform trade studies of the SPU design informed by the above laboratory studies, 3) design the system, identify components and vendors, and 4) determine whether the system should be built in house or purchased from a suitable vendor, and estimate cost for building it. Building the actual flight-like SPU is beyond the resources expected for the current CIF, but could be performed in a subsequent year.
This project is innovative because it uses a well-established technique in clinical and biotech laboratories, and pioneers its application for space. It addresses a long term need because searching for life is a key goal of NASA’s Mars program but current and planned missions carry no instrumentation capable of identifying life signatures. SOLID is also relevant to searching for life on other astrobiology targets beyond Mars such as Europa and Ecelidus. The SOLID instrument is the key element of the Icebreaker Discovery mission that Ames has been studying and developing for the last decade. By taking advantage of this opportunity to collaborate with Spain, we will be better prepared for this and other future opportunities for space flight missions to search for life.
We can succeed now because SOLID is already at high TRL, and we will work closely with our Spanish collaborators. The current technology represents ten years of science and engineering development in Spain. By collaborating with CAB, Ames stands to gain a leadership position in life detection technology in the USA.
We will identify the specific compounds to search for on Mars, write a scientific paper on the these results, and bring the SPU design to a level sufficient to start construction with parts vendors and costs identified. Resources from the CIF will enable a Space Act Agreement with Spain to perform the joint instrument development.
This proposal aligns with the national initiative in the bioeconomy. As described in the National Bioeconomy Blueprint “Expanding basic knowledge of living systems and their molecular machinery will inspire new concepts for the creation of artificial processes and products that will address current and future needs”. The discovery of evidence of life on another planet and insight into its biochemical nature will produce a major expansion in our basic knowledge and understanding of living systems. At present, all biological knowledge is based on only one example of life.
References: Stoker, C. et al. (2010), The habitability of the Phoenix landing site, J. Geophys. Res. DOI: 10.1029/2009JE003421.  McEwen, A. S. et al. (2011) Seasonal flows on warm Martian slopes, Science DOI:10.1126/science.1204816More »
Search for life on Mars is a goal of the Mars exploration program.
Governement of Spain, Centro de AstrobiologiaMore »
|Organizations Performing Work||Role||Type||Location|
|Ames Research Center (ARC)||Lead Organization||NASA Center||Moffett Field, California|
|Centro de Astrobiologia (INTA-CSIC)||Academia||Madrid, Outside the United States, Spain|