Number 12, December 10, 1990 by Phillip F. Schewe and Ben Stein
VENUS IS STILL VOLCANICALLY ACTIVE, new Magellan pictures suggest. For example, an Australian-sized lava flood north of Venus' equator contains no meteorite craters, implying that the lava is no more than tens of millions of years old. Magellan's chief scientist, Stephen Saunders of JPL, said at the Fall meeting of the American Geophysical Union (AGU) that most of Venus' impact craters were relatively young and that older craters were possibly covered by a number of great lava flows. (Associated Press, December 3, 1990. Contact at JPL; Jim Doyle, 818-354-5011.)
ASTEROID IMPACTS KILLED THE DINOSAURS : Although some scientists consider volcanoes and other phenomena to have contributed to the mass extinctions at the KT boundary, the impact explanation was shared by all the panelists at an AGU session devoted to the subject. "A few years ago, our problem was that we didn't have any craters to point our fingers at, whereas now we've got several," said Walter Alverez of UC Berkeley. "So now, maybe instead of a smoking gun we've got a smoking firing squad." At the session several scientists offered differing impact-related extinction scenarios featuring broiling-hot particles, acid rain, and tidal waves. (Los Angeles Times, December 5, 1990.)
WORLD CLIMATE CHANGE: Scientists participating in the Intergovernmental Panel on Climate Change (IPCC) summarized some of their findings at the AGU meeting (and in a report distributed there). The IPCC scientists "are certain" that "there is a natural greenhouse effect which already keeps the Earth warmer than it would otherwise be" and that emissions from human activities "will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface." The IPCC "calculates with confidence" that "carbon dioxide has been responsible for over half the enhanced greenhouse effect in the past, and is likely to remain so in the future." "Based on current model results," they predict that under a business-as-usual scenario, a "likely increase in global mean temperature of about 1 degree C above the present value by 2025 and 3 degrees C before the end of the next century" will occur, along with a rise of about 20 cm in global mean sea level by 2030. The IPCC report notes, however, that the anticipated greenhouse effects may be of roughly the same size as the natural variability of past temperature patterns and that "unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more. (William Sprigg, NOAA, 202-673-5360.)
THE KECK TELESCOPE , with only nine of its 36 hexagonal mirror segments installed, has recorded a photograph of NGC 1232, a spiral-armed galaxy 65 million light years away. Keck, the world's largest optical and infrared telescope, currently under construction on the summit of Mauna Kea in Hawaii, is scheduled to begin full operation late next year. With a ten-meter mirror, Keck will have four times the light gathering power of the 200-inch Hale Telescope. (Science News, December 1, 1990.)
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