Science news
ARCHAEOLOGY: Peru canals show early irrigation
In the Andean foothills of Peru, archaeologists found what they say is evidence for the earliest known irrigated agriculture in the Americas.
An analysis of four derelict canals, filled with silt and buried deep under sediments, showed that they were used to water cultivated fields 5,400 years ago, in one case possibly as early as 6,700 years ago, archaeologists reported in a recent issue of the Proceedings of the National Academy of Sciences. The canals are in the Zana Valley, about 40 miles from the ocean and more than 300 miles north of Lima.
Other scholars hailed the discovery as adding a new dimension to understanding the origins of civilization in the Andes. The canals are seen as the long-sought proof that irrigation technology was critical to the development of the earliest Peruvian civilization, one of the few major cultures in the ancient world to rise independent of outside influence.
SPACE: Rovers still exploring
Two years ago this week, NASA’s rover Spirit parachuted into the Martian atmosphere and, cocooned in protective airbags, bounced and rolled to a stop. Three weeks later, a second rover, Opportunity, landed safely on the other side of Mars.
The plan was for each rover to explore for 90 Martian days (each Martian day, called a Sol, is almost 40 minutes longer than an Earth day). But once they rolled off their platforms and began work, mission managers knew that the vehicles might survive longer than 90 days.
“I really thought we would get 120,” said Steven W. Squyres, a professor of astronomy at Cornell University and the mission’s principal investigator. “Maybe 150, and absolute maximum 180.”
Instead, Spirit’s jaunt has continued past its 700th Martian day. Opportunity is also doing well. Each has suffered some decay.
Opportunity has a balky shoulder joint on the arm that holds most of its instruments, and one of its turning motors has failed.But neither rover seems close to ruin.
Two Earth years equal just more than one Mars year, which means that the rovers have now seen one full cycle of seasons. “Once you’ve lived with these rovers for a full Martian year, you kind of get a feel for what the planet’s like,” Squyres said.
At Opportunity’s site, for instance, the skies turned cloudier in winter and became clear again as spring arrived. Meanwhile, dust devils swirled across the landscape most often during summer, especially at Spirit’s site.
Compiled from the Associated Press, Knight Ridder Newspapers and the New York Times
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