2001 Annual Science Report
NASA Johnson Space Center Reporting | JUL 2000 – JUN 2001
MILDI Development (dm)
The purpose of the MILDI project is to develop detection and quantification methods for a large number of organic compounds, many of which may be associated with life. The methods will be built into a small instrument designed for robotic missions to Mars, Titan, and other NASA targets.
The original acronym stems from Mars Immunoassay Life Detection Instrument. The NASA Fundamental Biology Program has supported Early development, but the project is transitioning over to an Astrobiology Institute project. Other acronyms used by us for the same general concept include MIDI (Mars Immunoassay Detection Instrument), PASO, Protein Array Sensor for Organics, and one or two others. The general principal is that using antibodies developed to react with them on either a specific or a class basis can do detection of organic compounds. The reaction triggers a fluorescence dye, and UV or near UV laser light can be used to trigger the fluorescence, the glow can be detected by a small CCD camera, and the brightness can be calibrated to the abundance of the target antigen. An array can be made by borrowing current DNA array technology so that a thousand or more different antibodies can be deposited at indexed locations on a small chip. Up to 10,000 different test sites on a single 2-3cm chip have already been demonstrated for this technology. Soil, rock, or ater containing unknown compounds can be extracted and the concentrated extract deposited on the chip. Examples of sought compounds include a large variety of proteins, polysaccharides, amino acids, PAHs, and hopenoids (for searching for remains of fossil life). The technique has potential picomole sensitivity for many compounds. Activation of the fluorescence component or dye associated with the antibody is automatic and readout can proceed after an appropriate time interval. This technique has been demonstrated on a number of antibodies and is the basis of clinical detection for many types of tissue, bacteria, viruses, and organic compounds. The antibody-antigen technique is used in the drugstore over-the-counter pregnancy test. It is very reliable and very cheap. A large number of normal fluorescence stains or dyes can also be included in the array in addition to the antibodies.
Progress during this past year includes assembling and coordinating the team, enlisting an experienced project manager, identification of several dozen initial appropriate antibodies, acquisition of some of the antibodies, outlining of a testing protecol, and engineering design of the instrument. The instrument concept has already been included on three of the Mars Scout technology development proposals. While none of the three were awarded development seed money, we anticipate that MILDI will be included on actual Scout proposals when that opportunity is available. We also intend to propose it for the 2007 Mars lander mission.
The basic concept and instrument design is also adaptable to laboratory use for Mars sample return testing for organics and for life. It may also have spinoff use in clinical laboratories, home health care, and biohazard detection.
PROJECT MEMBERS:David McKay
Juan Pérez Mercader
RELATED OBJECTIVES:Objective 1.0
Determine whether the atmosphere of the early Earth, hydrothermal systems or exogenous matter were significant sources of organic matter.
Describe the sequences of causes and effects associated with the development of Earth's early biosphere and the global environment.
Define how ecophysiological processes structure microbial communities, influence their adaptation and evolution, and affect their detection on other planets.
Identify the environmental limits for life by examining biological adaptations to extremes in environmental conditions.
Search for evidence of ancient climates, extinct life and potential habitats for extant life on Mars.
Refine planetary protection guidelines and develop protection technology for human and robotic missions.