Space probe discovers ‘giant spot’ on Neptune

Press, 28 June 1989, Page 19

Space probe discovers ‘giant spot’ on Neptune

NZPA-PA Pasadena A giant spot roughly 10,000 km wide has been discovered on the planet Neptune by the Voyager 2 space probe, scientists have reported. “It’s huge,” said physicist, Edward Stone, a Voyager project scientist for NASA. “It would be reasonable to suspect this is a large, hurricane-like storm system similar to the Great Red Spot” on Jupiter. Stone said Voyager 2 was still too far from Neptune to determine if winds were swirling within the spot. Jupiter’s Great Red Spot contains winds. y,

Scientists have not yet named Neptune’s spot, but are calling it “the dark spot” because it appears darker than the surrounding blue-greenish atmosphere. The colour of the spot will not be known until scientists process pictures through different colour filters, said Andrew Ingersoll, a planetary scientist at the California Institute of Technology. Voyager 2 is hurtling at more than 67,600km/h toward its August 24 close encounter with Neptune. The spacecraft will zip within 4830 km of the gaseous planet’s cloud tops — the closest of any of Voyager’s planetary-flybys.

Five hours later, it will fly within 40,230 km of Triton, one of Neptune’s two known moons. The Neptune encounter will be Voyager 2’s fourth and final planetary flyby since the probe was launched in 1977. It explored Jupiter in 1979, Saturn in 1981 and Uranus in 1986. Neptune’s dark spot is located at about 25 to 30 degrees latitude in the planet’s southern hemisphere, Ingersoll said. Voyager had also discovered a much smaller, rapidly changing white spot — about half the size of the dark spot — about 70 degrees south latitude. «

Mary Beth Murrill, a spokeswoman for the National Aeronautics and Space Administration’s Jet Propulsion Laboratory, said Neptune’s dark spot was first clearly recognised in still photographs taken by Voyager 2 in April. It is not as large as Jupiter’s Great Red Spot, which is 25,000 km across at its widest point — large enough to contain three Earths. Jupiter’s Great Red Spot was discovered more than 350 years ago. It is believed to be red because of organic chemicals, or possibly sulphur or phosphorus, trapped within it.

While hurricanes on Earth break up after a week or two, the storm in the Great Red Spot has remained intact for centuries, Ingersoll said. The absence of continents on giant gas planets such as Jupiter and Neptune may explain the persistence of the spots, he said. Continents may help dissipate hurricanes on Earth. Neptune is the solar system’s fourth largest planet and is usually the eighth planet from the sun. But because Pluto’s elongated elliptical orbit sometimes brings it closer to the sun, Neptune is currently the ninth and most distant planet from the sun.