By Marc Kaufman
Washington Post Staff Writer
Thursday, September 28, 2006
After an arduous 21-month journey, the Mars rover Opportunity edged close enough to the rim of a large crater yesterday to send back its first photos of the bottom and rocky sides of the dramatic site. What they showed left researchers increasingly confident that their robotic explorer had reached a scientific gold mine that will dramatically increase their understanding of the planet's history.
NASA scientists said the rover came within about 15 feet of Victoria Crater's rim and was scheduled to climb over a small sand dune last night and stop right at the crater's edge.
"The pictures we got tell us there is a tremendous amount of geologic information hidden in that crater," said Steven Squyres of Cornell University, principal science investigator for the mission. "What secrets it actually holds we won't know till we begin to get the data. But yesterday's picture alone makes the voyage worthwhile."
Opportunity, which has survived on Mars 10 times as long as initially was thought possible, traveled more than six miles to get to Victoria -- a pit created by an impact that is 200 feet deep and half a mile across. It is substantially larger than any crater explored so far by the twin Martian rovers, Opportunity and Spirit.
NASA scientists were ecstatic about the day's progress and images and said more is to come. The Opportunity team is scheduled to meet today to decide which of two rock promontories -- dubbed Cape Verde and Cabo Frio -- would give the rover the best view of Victoria. The outcroppings project into the crater, and scientists said they would allow the rover to take dramatic panoramic shots in color with its high-resolution camera.
W. Bruce Banerdt, a NASA project scientist, said yesterday's images showed some of the rock stratification that geologists associate with the earlier presence of liquid water. He said Martian geology appears to be similar to Earth's, although the long absence of water allows rocks to remain unchanged for much longer periods.
"We're seeing similar features [at Victoria Crater] as what we'd see on Earth," he said. "But instead of being tens of millions of years old, these Martian rocks are billions of years old."
The black-and-white image sent back by Opportunity showed craggy rock formations on some of the crater's walls, and sand dunes at its bottom. They also showed sandy landslides down several sides of the crater, slopes that Banerdt said may be used as paths for the rover to descend into the crater.
"We not only want to get better and better pictures of those rocks, but want to get the rover close enough that it can reach out and touch them," he said.
Opportunity, which is the size of a riding lawn mower, cannot go down into the crater right now because it is winter on Mars, and the rover's solar panels would not receive enough sunlight to power its motors or operate the radioisotope generator that keeps the robot heated when temperatures plunge lower than 100 degrees below zero Fahrenheit. But the shortest days of the Martian winter have passed, and the long spring and summer lie ahead. The Martian year is about twice as long as Earth's, as are all its seasons.
Maneuvering the robot so near a sharp drop-off is daunting, especially because it is now about 230 million miles away from Earth. But Opportunity has been programmed to be "self protective," the scientists said. While it responds to radio signals from Earth, it also can override them if its cameras and computers identify dangers in its path.
Squyres said that the terrain approaching Victoria Crater has been relatively benign, and that ultimately driving around it is plausible. NASA scientists say they expect the rover to remain at the crater for months.
"This crater is so much deeper than what we've seen before, and that means much more geologic history is exposed in the rocks," he said. "For a geologist, this is just a dream come true."