| SPIRIT WEAK,
OPPORTUNITY KNOCKS SECOND ROVER LANDS TONIGHT European spacecraft detects signs of water at south pole Saturday, January 24, 2004 NEWS 01A By Mike Lafferty |
 EUROPEAN SPACE
AGENCY VIA AP
A 3-D photo taken by Mars Express shows a channel formed by once-flowing water, scientists say. The area is 62 miles across. |
While NASA officials try to nurse the ailing Mars rover Spirit back to health, its twin is poised to land tonight on the opposite side of the planet.
Opportunity is expected to bounce-land on the Meridiani Planum, a flat area just south of the equator, around 9:05 p.m.
"Opportunity is great. It's fantastic,'' said Jaime Dyk, an entry-descent and landing-test engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
The spacecraft was launched July 7 from the Cape Canaveral Air Force Station in Florida. The twin rovers are on an $820 million mission to study the planet's geology and seek out evidence of water and ancient life.
While tracking Opportunity, NASA engineers are receiving only limited data from Spirit, which landed Jan. 3 on Mars. Its daily data transmissions were interrupted Wednesday. Early Thursday, NASA received a signal indicating the rover received a message from Earth.
Then there was silence for 24 hours.
The rover finally communicated for 10 minutes around 4:30 a.m. yesterday and transmitted "limited data'' for 20 minutes about an hour later, officials said. They called its condition "critical'' and said restoring it to full function could take several weeks.
Using a duplicate of the rover, mission controllers are trying to determine what caused the problem.
"There is no single fault that explains all that's observable,'' said Pete Theisinger, the mission project manager.
While NASA is nursing Spirit and guiding Opportunity, European scientists yesterday announced that a European Space Agency craft has found the most direct evidence of water in the form of ice on Mars, detecting molecules vaporizing from the Red Planet's south pole.
The Mars Express, launched last year, made the discovery with its infrared camera.
Scientists have long believed the planet's poles contain frozen water, but previous findings -- including NASA's Mars Odyssey orbiter's evidence of large amounts of ice -- were based more on inferences, European scientists said.
NASA scientists said that Mars Express offered further confirmation of what scientists have long known.
In Pasadena, mission controllers thought they might skip a planned course adjustment for Opportunity today.
"If it's not broke, don't fix it,'' Dyk said.
The last adjustment was Jan. 16, when flight engineers made a minor tweak to keep the craft on course and on time.
Without the correction, Opportunity would have landed about 239 miles southwest of its target.
"It's like trying to thread a needle from Pasadena to Washington D.C.,'' Dyk said.
Spirit landed about a mile from its bull's-eye in the Gusev Crater after a seven-month, 283-million-mile flight. Scientists think the crater could have been an ancient lake with streams flowing into it from nearby uplands.
Opportunity's target was chosen because it contains hematite, a mineral that forms in water on Earth.
The six-wheeled, 384-pound, golf-cart-size craft is an exact duplicate of Spirit.
Spirit did not roll off of its landing platform for 13 days after its arrival. Engineers likely will proceed at the same measured pace after Opportunity's bounce-landing tonight.
Both rovers are supposed to move as much as a mile during three months of exploration. They are packed with tools to photograph, scrape and drill rocks and soil, and examine its finds under its own microscope.
"I think we're going to have a successful landing,'' said Rongxing Li, an Ohio State University scientist working on mapping the terrain around the two rovers.
"I don't expect anything because the site is less challenging than Gusev. There are fewer rocks and the topography is flat.''
Opportunity will enter the thin Martian atmosphere at about 12,000 mph. A heat shield, parachute and rocket engines will slow the lander to about 54 mph before it is released.
The craft will be cushioned on impact by a complex of giant, heavy-duty air bags.
"Obviously, it worked on Spirit,'' Dyk said.
Information from the Associated Press was used in this report.
mlafferty@dispatch.com