An infrared telescope flown on the second flight of the space shuttle Columbia identified individual minerals on Earth from orbit and distinguished between two clays so similar that on Earth they can be differentiated only in laboratory tests.
"This is the first time we've been able to identify any mineral from space except limonite, which is an iron oxide mineral identified by the Landsat satellite five or six years ago," said Dr. Alexander F.H. Goetz of the Jet Propulsion Laboratory in Pasadena where the infrared instrument was built.
"This promises dramatic improvements in the use of satellite instruments for locating hidden mineral deposits and for geological mapping," he said.
The infrared telescope seven inches in diameter and mounted in the shuttle's cargo bay identified limestone deposits and two mineral-bearing clays called kaolinite and montmorillonite. The latter offers a strong surface clue to hidden oil deposits and the former an even stronger clue to hidden deposits of heavy metals such as gold, silver and copper.
"We still have not analyzed 95 percent of the measurements the instrument made from the shuttle," Goetz said in a telephone interview. "We believe by the time we've finished analyzing all our data we will have identified minerals like mica, talc, gypsum and serpentine, which is a rock type that provides surface clues for metals like nickel and chromium."
The telescope aboard Columbia operates in infrared wave lengths three times beyond the range of previous spaceborne telescopes. That allowed it to "see" sunlight reflected off the earth's surface and not just heat energy radiating into space from the surface. Many minerals have distinctive "signatures" based on the way they reflect sunlight.
The three minerals identified by the instrument were observed on the earth's surface in various regions of Egypt, where an Egyptian-American geologist named Farouk el-Baz happened to be last November at the time of the second shuttle flight.
El-Baz was able to verify the shuttle findings with his ground-based observations and with samples of two of the three minerals he collected on field trips in Egypt.
The instrument also sampled 50,000 miles of the earth's surface in the eastern United States, southern Europe, northern Africa, the Middle East and China. It took more than 400,000 mineral readings of the earth's surface not under cloud cover during the three days the shuttle was in orbit.