NASA's Spirit rover completed its first full day on Mars Sunday, sending back black-and-white pictures of its Gusev Crater landing site, the first of a stream of images that are eventually expected to reveal the Martian surface in unprecedented detail.
The rover sent an initial burst of data and pictures back to Earth within hours of its landing Saturday night, then twice communicated with Earth during the long Martian night.
Most of the information sent Sunday was technical data. No new images were released beyond the initial 64 taken shortly after landing.
A hurried analysis of the pictures indicated that Spirit had landed within 6 miles of the center of its elliptical target in the middle of the massive Gusev Crater, a feat that team members compared to threading a needle from 15 miles away.
Researchers were overjoyed by the terrain revealed by the pictures. "It's a place almost tailor-made for our vehicle," said Steve Squyres of Cornell University, the mission's principal investigator. "It's a glorious crater. We have hit what the science team believes is the scientific sweet spot."
Although controllers do not yet know the precise location of Spirit, a photo of the general area of the landing site previously taken by Mars Odyssey indicates it is laced with dark trails formed by dust devils -- mini-tornadoes common on the Martian surface. The trails will provide the rover with easy access to the layers of rock underlying the dusty Martian surface.
"What we wanted was someplace where the wind ... has cleaned off the rocks for us so we wouldn't be totally occupied with doing that ourselves," Squyres said.
The pictures also showed that the area was littered with medium-sized rocks ideal for examination by the rover's sophisticated instruments, and few large boulders that could impair its movements.
Also nearby are depressions that appear to be rimmed with sharp edges that make them ideal places to search for layers within the rocks that may indicate that water once filled Gusev. They are also filled with fine soil, making them possible "rover traps" that will require the utmost caution, Squyres said.
"But we have six legs, and we might dip one toe in them," he added.
Shortly after bouncing to its near-perfect landing Saturday evening, Spirit took a rapid-fire series of pictures with its low-resolution navigation camera, sending them back to Earth via the Mars Odyssey orbiter. It then went into "sleep" mode to preserve its batteries during the frigid Martian night.
The images confirmed that Spirit had survived its "six-minutes-from-hell" descent Saturday evening in near-perfect fashion. It bounced for about a mile before settling down in a upright position, the best scenario imaginable.
The craft awoke twice during the night to send 12- and 16-minute bursts of data to NASA's Mars Global Surveyor and Mars Odyssey orbiters for relay to Earth.
Mission controllers at NASA's Jet Propulsion Laboratory in Pasadena then woke it up at 2:45 p.m. Sunday, shortly after Martian sunrise, by playing the Beatles' "Good Morning, Good Morning," -- a tradition that began with the Mars Pathfinder mission.
The craft also transmitted data indicating that it was in good condition. The only potential concern is that dust in the Martian atmosphere is reducing the amount of sunlight reaching the rover's solar panels to about 83% of the predicted value. That limits the amount of power available to the rover's instruments, but controllers do not expect the condition to persist.
"If there is one thing that is sure, it is that the Martian atmosphere will change," said Firouz Naderi, Mars exploration program manager at JPL.
Sunday on Mars was devoted to making sure the rover was functioning properly, unfolding its high-gain antenna that is used for direct communications with Earth and taking better pictures of the landing site.
The golf cart-sized Spirit has three antennas: a UHF, or ultrahigh frequency, antenna to communicate with passing orbiters and both low- and high-gain antennas for communicating directly with Earth.
The more powerful antenna will let controllers interact with the rover without relaying their commands through a satellite. But they are not able to control the rover's activities in real time because of the nearly 12 minutes required for a radio signal to travel between Mars and Earth.
Controllers also wanted to take a closer look at what initially appeared to be a large rock very close to the lander that might have impaired their ability to drive the six-wheeled rover off its platform. They eventually concluded that the object was actually a very dirty air bag -- part of the air bag cocoon that cushioned the craft's landing.
The rest of this week will be spent checking out the rover, releasing it from the straps that bind it to the lander, and photographing the landing site with the two high-definition color cameras that will provide stereo images with a resolution 14 times better than that of the pictures initially released.