Mars orbiter detects extensive ice sheets

`Whopping large signal' in search for water surprises researchers

March 02, 2002|By LOS ANGELES TIMES

PASADENA, Calif. - Just days after starting its science mission, a new spacecraft orbiting Mars has struck paydirt, detecting vast fields of ice that scientists say provide evidence of sufficient water to make it possible for the planet to have harbored life.

The discovery is a coup for NASA, whose leaders are using a "follow the water" strategy to understand the evolution of Mars and look for signs of past and present life there. The presence of water would also be key to any future attempt to have astronauts explore the Martian surface.

"Water is vital to life. Water has changed the surface of Mars in the past. And water is essential to the future exploration of Mars," R. Stephen Saunders, the Jet Propulsion Laboratory's project scientist for the Odyssey orbiter, said at a media conference yesterday at JPL.

Results from planetary missions often take months, if not years, to be collected, analyzed and released to the public. The new results are unusual because they come so early in the mission, "from the first few days, in some cases the first few hours, of exploration," Saunders said.

The normally cautious scientists were able to make strong conclusions so quickly because "we really have a whopping large signal," said William Boynton, a planetary scientist from the University of Arizona who directs the instrument that detected the ice. "It really just blew us away when we looked at it."

Boynton's team used a gamma ray spectrometer to probe the chemistry of the Martian surface. The instrument can detect the chemical constituents on the surface, including the hydrogen atoms contained in water molecules, by analyzing the unique gamma ray signatures emitted by each element.

The instrument has been called a "virtual shovel" because it can read signals from underneath the ground, in the shallow surface layers of Mars.

"The signal we're getting is loud and clear. There's lots of ice on Mars," Boyton said. "We're not just looking at surface frost. It's a fair amount of ice."

Scientists have long known that Mars had some water. But until now, they lacked enough data to tell whether water was found only in a few isolated places or was widespread on the planet's surface. The wider the distribution of water, the more chance there may have been for life to develop on the planet, scientists believe.

The ice was found on the southern hemisphere of the planet, where it is now approaching fall. Scientists know the water is frozen, Boyton said, because of temperature readings showing that "it's just too darn cold for it to be liquid."

Boynton could not quantify the amount of ice found. The findings are so new that his team had not yet done the calculations necessary to make such an estimate.

Odyssey, the first spacecraft to reach Mars since two Mars missions failed in 1999, will enable scientists to conduct the first chemical analysis of the entire Martian surface and map the surface with great detail. The instrument doing much of this work is a thermal-emission camera called "Themis" that takes regular images of the surface during the day and takes infrared images at night.

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