Page:Concepts for detection of extraterrestrial life.djvu/45

 CHAPTER IX

This instrument, named after Swift’s famous fictional traveller to strange places, is designed to search for microbial life on Mars. The project scientists for NASA are Dr. Gilbert V. Levin of Hazleton Laboratories, Inc., and Dr. Norman H. Horowitz of the California Institute of Technology.

Gulliver consists of a culture chamber that inoculates itself with a sample of soil. The chamber contains a broth whose organic nutrients are labeled with radioactive carbon. When micro-organisms are put into the broth they metabolize the organic compounds, releasing radioactive carbon dioxide. The radioactive carbon dioxide is trapped on a chemically coated film at the window of a Geiger counter. The counter detects and measures the radioactivity; this information will be conveyed to a radio transmitter which will signal it to Earth. Gulliver can detect growth, as well as metabolism, by virtue of the fact that the rate of carbon dioxide production increases exponentially (geometrically) in growing cultures. Exponential production of carbon dioxide would provide strong evidence for life on Mars and would make it possible to estimate the generation time; that is, the time required for doubling the number of organisms in the culture.

In addition to a culture chamber and counter (actually a group of counters in anticoincidence circuitry), Gulliver contains a built-in sample collector. This mechanism consists of two 25-foot lengths of kite line and chenille wound on small projectiles. The windings are made in the manner of harpoon lines to prevent snagging, and the strings are coated with silicone grease to make them sticky. When the space package arrives on Mars, a miniaturized programmer will take charge of Gulliver (actually, at least two Gullivers will be used, one as a test instrument and the other as a control). The projectiles will be fired, deploying the lines over the surface of the planet. A tiny motor inside the chamber will then reel in the lines, together with adhering soil particles. After line retrieval, the chamber of Gulliver will be sealed, and an 35