Land Sighted On Mercury

Press, Volume CX, Issue 32359, 27 July 1970, Page 7

Land Sighted On Mercury

(N.Z. Press Assn.—-Copyright)

NEW YORK.

Land has been sighted on the planet Mercury for the first time, but nobody is yet sure whether the topographical features seen are mountains, boulder fields, craters, or what.

This is because scientists have only low-power radar signals to work with. Initial radar observations of the planet were made late last year by radar astronomers at the Goldstone tracking station in Pasadena, California. But the news that there are Continentsized rough spots on the planet has only recently been announced by Dr" Richard Goldstein, head of the com-munications-research station. The time lag resulted from the months it took to interpret and assemble the spectrographic evidence. Dr Goldstein reported the Mercury radar studies at a meeting of the United States national committee of the International Scientific Radio Union in Washington.

It is the first time radar astronomers have been able to identify strong features on Mercury, Dr Goldstein said, mainly because it is the first time that more powerful radar signals have been beamed at the planet. He said that the discovery in itself came as no great surprise. Similar features had been observed on the planet Venus much earlier, because Venus being closer to Earth—is a better target for exploration by radar.

The, technique of determining what the surface of Mercury is like involved using a 450-kilowatt power radar transmitter coupled with a 210 ft dish receiver to pick up the returning echoes. When Mercury swings around closest to the Earth in its orbit around the sun (this happens three times a year), it becomes a target for Earth-generated radar waves. The waves, pulsed out with the intensity of a lion’s roar, return in 10 minutes with the weakness of a mouse’s squeak. Signals were alternately transmitted and received for six days. Then the evidence was compiled in spectrographic terms, something like blueprints, showing the reflectivity of substances on the planet’s surface.

The probing by radar indicated to scientists that Mercury possesses a series of large topographic features—shown as rough spots on the spectrograms—which stretch along an 800-mile tract near the planet’s equator. The radio astronomers also located one small smooth area on the equator of Mercury. Mercury is difficult to Observe with telescopes, Dr Goldstein said, because of its close proximity to the Sun. The rough features on Mercury were similar to one observed on Venus except

that .the “land” on Mercury seems to have less contrast.

Mercury was roughly 55 million- miles from the Earth at the time the observations were made, he noted, presenting “a very difficult target, having about the radar effectiveness of a dime at 10,000 miles.”