The Ps-aerogel system [Ps is positronium (an electron-positron-hydrogen-like atom)] has been evaluated and optimized as a potential tool for planetary exploration missions. Different configurations of use were assessed, and the results provide a quantitative measure of the expected performance. The aerogel density is first optimized to attain maximum production of Ps that reaches the pores of the aerogel. This has been accomplished, and the optimum aerogel density is ≈70 mg/cm3. The aerogel is used as a concentrator for target volatile moieties, which accumulate in its open porosity over an extended period of time. For the detection of the accumulated materials, the use of Ps as a probe for the environment at the pore surface, has been proposed.

This concept is based on two steps: (1) using aerogel to produce Ps and (2) using the propensity of Ps to interact differently with organic and inorganic matter. The active area of such a detector will comprise aerogel with a certain density, specific surface area, and gas permeability optimized for Ps production and gas diffusion and adsorption. The aerogel is a natural absorber of organic molecules, which adhere to its internal surface, where their presence is detected by the Ps probe. Initial estimates indicate that, e.g., trace organic molecules in the Martian atmosphere, can be detected at the ppm level, which rivals current methods having significantly higher complexity, volume, mass, and power consumption (e.g. Raman, IR).

This method carries important benefits in working toward NASA/JPL goals, and has the potential to advance organic detection capabilities. It is intended to work toward feasibility studies. At the same time, it is recognized that a full-scale investigation will profit enormously from an achieved optimization of the aerogel microstructure for Ps production and gas percolation.

The Ps-aerogel system provides an entirely new approach toward sensing of trace volatile components in vacuum or in the atmosphere. Contrary to all other conventional methods, which use “momentary sensing” and analyzing the content, the Ps-aerogel system relies on a continuous passive exposure to the environment. An instrument built on this new technology will be lightweight, small in size, and will not consume power during accumulation. In testing, the adsorption of simple organic materials, such as alcohols, naphthalene, etc, has been detected. Also, with the optimization of the Ps-aerogel system, a number of other applications, ranging from thermal insulation to charge storage systems, have been discovered.

This work was done by Mihail P. Petkov and Steven M. Jones of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at under the Physical Sciences category. NPO-46762

This Brief includes a Technical Support Package (TSP).
Aerogel-Positronium Technology for the Detection of Small Quantities of Organic and/or Toxic Materia

(reference NPO-46762) is currently available for download from the TSP library.

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This article first appeared in the October, 2010 issue of NASA Tech Briefs Magazine.

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