Plumes spewing from Saturn moon may contain water

WASHINGTON – Astronomers looking at the spectacular supersonic plumes of gas and dust shooting off one of Saturn's moons say there are strong hints of liquid water, a key building block of life.

Their research, appearing in Thursday's issue of the journal Nature, adds to the growing push to explore further the moon Enceladus, as one of the solar system's most compelling places for potential life.

Using images from NASA's Cassini probe, astronomers had already figured that the mysterious plumes shooting from Enceladus' icy terrain contain water vapor. New calculations suggesting the gas and dust spew at speeds faster-than-sound make the case for liquid, said study lead author Candice Hansen of NASA's Jet Propulsion Lab in California. Her team calculated the plumes travel more than 1,360 mph.

Reaching that speed "is hard to do without liquids," Hansen said. While her paper offers more evidence building on what others have found, she added that her research is not the final proof of liquid water on Enceladus (pronounced en-SELL-ah-dus).

Other planetary scientists, such as Andrew Ingersoll at the California Institute of Technology, said the research is good, but that it is possible to achieve such speeds with ice particles and at cooler temperatures. So Hansen hasn't proven her case yet, he and other scientists said.

Carolyn Porco, the head of the Cassini camera team and an astronomer who didn't take part in Hansen's research, said "the evidence in my mind is building on liquid water." That moon, one of 60 circling Saturn, "has become the go-to place" for exploration in the outer planets, she said.

Europa, a moon of Jupiter, may have a liquid ocean beneath its frozen surface. But Enceladus, thought responsible for producing one of Saturn's rings, is more accessible, Hansen said. "Enceladus is sort of helpfully spewing out its innards," she said.

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Cold front could thwart Friday's shuttle launch

CAPE CANAVERAL, Fla. – An approaching cold front could thwart NASA's plans to launch space shuttle Endeavour on Friday on a flight to the international space station.

But the seven astronauts arrived Tuesday ahead of the countdown start and hopeful for an on-time liftoff.

"This mission is all about home improvement, home improvement both inside and outside," shuttle commander Christopher Ferguson said after arriving from Houston with his crew.

During the 15-day mission, the astronauts will deliver a new bathroom, kitchenette, two bedrooms and exercise machine, as well as a water recycling system — and a new resident for the space station. A new astronaut will replace one of the three space station residents.

The plan is to expand the living quarters of the space station so the crew can be doubled to six by next June.

"On the inside of the space station, the walls are largely up," Ferguson said. "... Well, it's moving day. It's time to fill them up."

Ferguson also noted the never-before-attempted repairs that are planned for outside the space station. Three of the crew will take turns going outside to clean and lubricate a clogged joint that is preventing one set of solar wings from turning automatically toward the sun, and they'll replace its bearings.

This will be NASA's first shuttle launch since the end of May.

"We haven't had a launch for a while, so we're really excited to be back in the saddle again," said test director Jeff Spaulding.

The threatening cold front was moving across the central part of the nation Tuesday and was expected to bring rain and thick clouds to the launch site by week's end.

Shuttle weather officer Kathy Winters said there was a 60 percent chance of acceptable conditions at the 7:55 p.m. Friday liftoff time and only a 40 percent chance on Saturday.

"The timing of the front will be critical," she said.

NASA has a shuttle launch window until Nov. 25.

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Ancient cave yields clues to Chinese history

WASHINGTON – A stalagmite rising from the floor of a cave in China is providing clues to the end of several dynasties in Chinese history. Slowly built from the minerals in dripping water over 1,810 years, chemicals in the stone tell a tale of strong and weak cycles of the monsoon, the life-giving rains that water crops to feed millions of people.

Dry periods coincided with the demise of the Tang, Yuan and Ming dynasties, researchers report in Friday's edition of the journal Science.

In addition, the team led by Pingzhong Zhang of Lanzhou University in China noted a change in the cycles around 1960 which they said may indicate that greenhouse gases released by human activities have become the dominant influence on the monsoon.

The Wanxiang Cave is in Gansu Province, a region where 80 percent of the rainfall occurs between May and September.

Chemical concentrations in the stalagmite indicate a series of fluctuations lasting from one to several centuries and roughly similar to records of the Little Ice Age, Medieval warm period and Dark Age cold period recorded in Europe.

There were decade-long fluctuations between A.D. 190 and 530, the end of the Han Dynasty and most of the Era of Disunity, the researchers said. From 530 to 850 the monsoon declined, covering the end of the Era of Disunity, the Sui Dynasty and most of the Tang Dynasty.

The monsoon remained weak, with another sharp drop between 910 and 930, then it rose sharply over 60 and remained strong until 1020.

The researchers found that after 1020 the monsoon varied but was generally strong until a sharp drop between 1340 and 1360: the mid 14th-century monsoon weakening. It stayed weak, with substantial fluctuation, until a sharp increase between 1850 and 1880.

According to the researchers, the 9th-century dry period contributed to the decline of the Tang Dynasty and the Mayans in Mesoamerica. It also may have contributed to the lack of unity during the Five Dynasties and Ten Kingdoms period, they said.

The following strengthening of the monsoon may have contributed to the rapid increase in rice cultivation, the dramatic increase in population, and the general stability at the beginning of the Northern Song Dynasty, they suggested, adding that the end of the Yuan and the end of the Ming are both characterized by unusually weak summer monsoons.

The research was supported by the National Science Foundations of the United States and China, the Gary Comer Science and Education Foundation, the Ministry of Science and Technology of China and the Chinese Academy of Sciences.

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