Silicon specific radioactivity

In a DNA array, gene-specific probes are created and immobilized on a chip (silicon wafer, nylon or glass array substrate). Biological samples are labeled with fluorescent dyes or radioactivity. These labeled samples are then incubated with the probes to allow hybridizations to take place in a high fidelity manner. After incubation, non-hybridized samples are washed away and spot fluorescent or radioactivity signals resulting from hybridization can be detected. 

All Mars rovers to date have carried alpha-particle X-ray spectrometer (APXS) instruments for chemical analyses of rocks and soils (see Fig. 13.16). The source consists of radioactive curium, which decays with a short half-life to produce a-particles, which then irradiate the sample. Secondary X-rays characteristic of specific elements are then released and measured by a silicon drift detector. The Mars Pathfinder APXS also measured the backscattered a-particles, for detection of light elements, but the Mars Exploration Rovers measured only the X-rays. 

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