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©P. C. Frisch, University of Chicago |
The Sun and the nearest stars move through filaments of galactic clouds. |
Earth Changes
Until ten years ago, most astronomers did not believe stardust could enter our Solar System. Then ESA's Ulysses spaceprobe discovered minute stardust particles leaking through the Sun's magnetic shield, into the realm of Earth and the other planets. Now, the same spaceprobe has shown that a flood of dusty particles is heading our way.
That's just one of the surprising discoveries that have resulted from the extended life of NASA's Mars Global Surveyor, which this month began its ninth year in orbit around Mars. Boulders tumbling down a Martian slope left tracks that weren't there two years ago. New impact craters formed since the 1970s suggest changes to age-estimating models. And for three Mars summers in a row, deposits of frozen carbon dioxide near Mars' south pole have shrunk from the previous year's size, suggesting a climate change in progress.
"Our prime mission ended in early 2001, but many of the most important findings have come since then, and even bigger ones might lie ahead," said Tom Thorpe, project manager for Mars Global Surveyor at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The orbiter is healthy and may be able to continue studying Mars for five to 10 more years, he said.
Mars years are nearly twice as long as Earth years. The orbiter's longevity has enabled monitoring of year-to-year patterns on Mars, such as seasonal dust storms and changes in the polar caps. "Mars is an active planet, and over a range of timescales changes occur, even in the surface," said Dr. Michael Malin of Malin Space Science Systems, San Diego, principal investigator for the Mars Orbiter Camera on Mars Global Surveyor.
Odyssey has been mapping the distribution of materials on and near Mars' surface since early 2002, nearly a full annual cycle on Mars. Besides tracking seasonal changes, such as the advance and retreat of polar dry ice, the orbiter is returning evidence useful for learning about longer-term dynamics.
The amount of frozen water near the surface in some relatively warm low-latitude regions on both sides of Mars' equator appears too great to be in equilibrium with the atmosphere under current climatic conditions, said Dr. William Feldman of Los Alamos National Laboratory, N.M. He is the lead scientist for an Odyssey instrument that assesses water content indirectly through measurements of neutron emissions.
"One explanation could be that Mars is just coming out of an ice age," Feldman said. "In some low-latitude areas, the ice has already dissipated. In others, that process is slower and hasn't reached an equilibrium yet. Those areas are like the patches of snow you sometimes see persisting in protected spots long after the last snowfall of the winter."
Frozen water makes up as much as 10 percent of the top meter (three feet) of surface material in some regions close to the equator. Dust deposits may be covering and insulating the lingering ice, Feldman said. He and other Odyssey scientists described their recent findings today at the fall meeting of the American Geophysical Union in San Francisco.
Energy Secretary Samuel Bodman warned against "unintended consequences" - including job losses - that he said might result if the government requires economy-wide caps on carbon dioxide from the burning of fossil fuels.
Comment: Excuuuuse us! But hasn't the U.S. already lost most of its industry to "outsourcing"? Isn't the U.S. economy already severely damaged by Bush's warmongering and tax cuts for the rich?