BY JUSTIN RAY

Follow the missions of NASA's "Spirit" Mars Exploration Rover-A and "Opportunity" MER-B on the Red Planet! Reload this page for the very latest on both rovers. Use our text only page for faster downloads.

WEDNESDAY, MARCH 31, 2004
Opportunity resumed science operations after waking to Aerosmith's "Back in the Saddle" on its 65th sol, which ended at 2:02 a.m. PST on March 31. During the martian morning, the miniature thermal emission spectrometer and panoramic camera studied the atmosphere. "Bounce" rock was imaged by the panoramic camera.

Opportunity's instrument arm was then deployed to get a close-up view of "Bounce" using the microscopic imager. The rock abrasion tool team used some of these images to identify the exact target for next sol's grinding operation. The Moessbauer spectrometer was then placed on a designated target on the rock for an overnight integration.

In the afternoon, Opportunity took navigation and panoramic camera images and completed more miniature thermal emission spectrometer science.

Next sol, the rover's rock abrasion tool will grind into Bounce.

Spirit began sol 86, which ended at 2:20 p.m. PST on March 31, 2004, by waking up and heating the panoramic mast assembly to complete sky and ground stares with the miniature thermal emission spectrometer. Spirit completed the alpha particle X-ray spectrometer integration on the hole made by the rock abrasion tool and then took a 45-minute nap.

Once Spirit woke up, it began the 6-position rock abrasion tool brush mosaic on the target Missourion the rock called Mazatzal. Once this was completed successfully, the rovers arm was stowed.

Spirit then rolled backwards .9 meters (2.95 feet) to correctly position itself to acquire mini thermal emission spectrometer imaging of the newly brushed mosaic, and the previously ground hole. In addition, Spirit took sky and ground stares and panoramic camera images of the upcoming drive direction. The sol ended with mini thermal emission spectrometer stares at the Columbia Hillsand an afternoon pass by NASAs Mars Odyssey orbiter.

Sol 87, which ends at 3:00 p.m. PST on April 1, 2004, will be a driving day for Spirit as it begins what could be a record-breaking journey toward the Columbia Hills.

TUESDAY, MARCH 30, 2004
Since the rock abrasion tool completed a full-circle grind into the "New York" and "Brooklyn" targets on the rock "Mazatzal," it was time for Spirit to do some analysis. Spirit spent much of Sol 85, which ended at 1:41 p.m. PST on March 30, successfully operating the instruments on its robotic arm to take a more detailed look inside Mazatzal.

Although all the operations were completed successfully on Mars, the rover team spent most of the morning and afternoon on Earth worrying. After the team sent the uplink to Spirit, they waited for the standard "beep" that confirms the sequence reached Spirit and was activated. This beep, and an expected one 10 minutes later were not acquired, and engineers proceeded to trouble-shoot what might have gone wrong. No errors could be found, and finally a successful afternoon Odyssey communications pass provided 75 megabits of data, indicating that all the sequences were in fact onboard the rover and that all the planned sol activities had completed successfully. Like worried parents, the rover team members breathed a collective sigh of relief, and are now looking into possible causes of the failure to detect the beep.

As planned, Spirit began sol 85 by receiving the uplink and then taking a one-hour nap. After waking, the rover took panoramic camera images of the rock abrasion tool and of the ratted hole in Mazatzal. Before the panoramic camera work was done, Spirit took some final shots of "Bonneville" crater. Some of those images might contribute to a super-resolution image of the heatshield remnants on the far wall. Spirit also took some images to try to catch a dust devil in action.

After the panoramic camera activity, Spirit used the microscopic imager to take a 5-position pseudo-color mosaic of the Mazatzal rock abrasion tool hole. Then the Moessbauer spectrometer was placed in the hole and began an overnight integration.

A little after 2 p.m. Mars Local Solar Time, the last miniature thermal emission spectrometer sections of Bonneville crater were acquired, followed by a set of panoramic camera images of the drive direction. In the late afternoon, Spirit used the mini thermal emission spectrometer to acquire ground and sky stares, which will be complemented by another set early tomorrow morning. Shortly after the 2 a.m. Mars Global Surveyor pass, the arm will change tools from the Moessbauer spectrometer to the alpha particle X-ray spectrometer for an integration in the rock abrasion tool hole through 9:20 a.m Mars Local Solar Time on Sol 86.

The rock abrasion tool will be back to work on sol 86, which will end at 2:20 p.m. PST on March 31, 2004, brushing a 6-spot mosaic on another portion of the rock Mazatzal called "Missouri." The mini thermal emission spectrometer will analyze the brushed area and then Spirit will begin a 5-sol drive toward the Columbia Hills.

On Opportunity's 64th sol, which ended at 1:22 a.m. PST on March 30, the rover team analyzed the results of engineering activities run to investigate an error message they received from the rover on sol 63.

A problem with a secondary memory file was isolated and resolved. Just as an ordinary computer disk can have corrupted sections, a corrupted file in an area where rover commands are addressed and stored has been identified. Engineers have identified the location of the problem within the memory and figuratively fenced it off, containing it and preventing it from harming any future command sequences. This minor issue has not impeded the rover from resuming normal science operations on the next sol.

The wake-up song chosen for Opportunity on this quiet sol was "Stand" by REM.

The rover is currently at the rock dubbed "Bounce." Opportunity met this rock once before; while still cloaked in its protective lander and airbags, the rover bounced on the rock while on its way to a safe landing in "Eagle Crater." Miniature thermal emission spectrometer observations have shown Bounce is rich in hematite. In the coming sols, the rover's other spectrometers will examine the rock before the rock abrasion tool grinds into a designated target.

SUNDAY, MARCH 28, 2004
The angular nature of the rock called "Mazatzal" required some extra rodent power over the weekend. The latest grind by Spirit's rock abrasion tool (the RAT) resulted in that tool's deepest hole yet, nearly 8 millimeters (0.31 inches.) The rover was inspired to tackle the target "Brooklyn" right next to its "New York" bull's-eye by the Beastie Boys' "No Sleep Till Brooklyn" on its 83rd sol, which ended at 12:22 p.m. PST on March 28.

Spirit's 84th sol, which ended at 1:01 p.m. PST on March 29, was planned as a day of investigation. The miniature thermal emission spectrometer and panoramic camera made successful observations of the crater informally named "Bonneville," but planned operations of the rover arm were not executed due to a switch on the Moessbauer spectrometer getting momentarily stuck. After a successful Moessbauer integration, the instrument was pulled back from Mazatzal, but one of two contact switches did not indicate a no-contact condition. Although the instrument had been retracted, the rover's software interpreted this as an unexpected collision of the spectrometer with an object, so it terminated any further arm operations. The stuck switch flipped about three minutes later but the rover is programmed to wait until the false error is cleared by mission control.

On sol 85, Spirit will retake microscope images of areas on Mazatzal, and overnight Moessbauer and alpha particle X-ray spectrometer integrations will be repeated.

FRIDAY, MARCH 26, 2004
Spirit began sol 81, which ended at 11:02 a.m. PST on March 26, 2004, by stopping the alpha particle X-ray spectrometer integration and then imaging the instrument's placement with the hazard avoidance camera. The rest of this sol was all about grinding into the target "New York" on the rock named "Mazatzal."

The rock abrasion tool operated on the New York target for three hours and forty-five minutes and created an impression in the rock that was 3.79 millimeters (.15 inches) deep. The angular shape of Mazatzal and the fact that the rock is a little harder than previously abraded rocks allowed the more flat side of the circular target to receive a more intense grind. On sol 83, the science and engineering teams plan to again place Spirit's rock abrasion tool onto the rock, overlapping the already abraded area and reaching the area just to the left.

Spirit will spend most of sol 82, which will end at 11:42 a.m. PST on March 27, 2004, analyzing the rock abrasion tool impression with the microscopic imager, Moessbauer spectrometer and alpha particle X-ray spectrometer. The rover will also place the microscopic imager over a clean surface to the upper left of the ratted area and take some images.

The wake-up song today was "Boy from New York City" by The Manhattan Transfer, in honor of the grind on the New York target.

Spirit's odometer now reads: 492 meters - more than a quarter of a mile!

On sol 60, which ended at 10:44 p.m. PST on March 25, NASA's Mars Exploration Rover Opportunity had a quiet day continuing its research around the exterior of Eagle Crater.

Opportunity changed tools from the Moessbauer spectrometer to the alpha particle X-ray spectrometer around 11:30 Local Solar Time. In addition to the tool change, Opportunity took a comprehensive color high-resolution panorama with the panoramic camera. The rover team dubbed it the "Lion King Panorama" because it is a look around Opportunityıs domain from a high vantage point -- much like the view from "Pride Rock" in The Lion King movie. The large panorama essentially filled the remaining flash memory volume onboard the spacecraft, requiring a plan for sol 61 that minimizes data collection. The miniature thermal emission spectrometer also collected remote sensing data.

The wake up song for sol 60 was ³The Circle of Life² by Elton John in honor of the Lion King panorama.

The plan for sol 61, which will end at 11:23 p.m. on March 26 PST, is to drive north to an area with dark material.

THURSDAY, MARCH 25, 2004
Here are the latest Spirit and Opportunity official status reports from mission control:

On sol 80, which ended at 1823 GMT on March 25, NASA's Mars Exploration Rover Spirit repeated overnight measurements of "Illinois" and "New York," two targets on the rock "Mazatzal." The measurements needed to be repeated because the alpha particle X-ray spectrometer's doors inadvertently did not open during the prior sol. In honor of doors being stuck partially open, sol 80's wake up song was "Open the Door" by Otis Redding.

Mazatzal is one of an apparent class of "light-toned rocks," which may be common in the area where Spirit landed in Gusev. This rock appears to be a "ventifact," which means it may have been carved by the steady winds that scientists know come from the northwest into the top area of this crater rim.

The plan for sol 81, which will end at 1902 GMT on March 26 PST, is to grind into Mazatzal with the rock abrasion tool.

Opportunity spent sol 59, which ended at 0604 GMT, placing the Moessbauer spectrometer on the bright material it approached yestersol, and conducting more remote sensing observations.

This relatively light workload allowed the rover to recover energy for the next sol's activities. Those will include completing an alpha particle X-ray spectrometer read on the same soil target and initiating the panoramic mosaic image from the rover's current position.

The wake-up tune for the sol was "59th Street Bridge Song (Feeling Groovy)" by Simon and Garfunkel.

WEDNESDAY, MARCH 24, 2004
Here are the latest Spirit and Opportunity official status reports from mission control:

NASA's Mars Exploration Rover Spirit awakened at 9:35 a.m. Mars Local Solar Time on Sol 79, which ended at 1743 GMT on March 24. An early morning review of the alpha particle X-ray spectrometer data revealed that the instrument's doors were not fully open and that the tool did not completely engage at the intended "New York" target on the rock dubbed "Mazatzal." The alpha particle X-ray spectrometer integration on "New York" will be repeated on sol 80.

Spirit took a nap until 12:45 Mars Local Solar time to conserve power for the upcoming grind on Mazatzal on sol 81. Once the rover woke up, it began the sequences of brushing and analyzing two targets, "New York" and "Illinois," on Mazatzal. Each target was brushed with the rock abrasion tool and then imaged with the microscopic imager and panoramic camera. The entire sequence ended with a Moessbauer spectrometer integration on the New York target.

Rover controllers plan to let Spirit rest until 4 a.m. Mars Local Solar time on Sol 80, when the tools on the robotic arm will be changed to place the alpha particle X-ray spectrometer on the brushed New York target. The rest of sol 80, which will end at 1823 GMT on March 25, will be spent analyzing the brushed and unbrushed areas of Mazatzal with the instruments on the rover's robotic arm.

The song "Come on Home" by Lambert, Hendricks and Ross beckoned Opportunity back toward its landing site crater to an area of bright material. The rover also began to image a panoramic mosaic of the plains on this sol, which ended at 0525 GMT on March 24.

Over the martian night, Opportunity will again wake up to take miniature thermal emission spectrometer measurements.

In the coming sols, the rover will use its spectrometers to investigate the bright material area and then move on to a specific target in the area dubbed "Bright Spot."

TUESDAY, MARCH 23, 2004
Here are the latest Spirit status report from mission control:

NASA's Mars Exploration Rover Spirit woke up at 7:24 a.m. Mars Local Solar time on sol 78, which ended at 1704 GMT on March 23, 2004, and began a day of observations in preparation for the sol 79 grind on the rock called "Mazatzal."

After waking, Spirit warmed-up the mast actuators for some early morning soil and atmosphere miniature thermal emission spectrometer observations. It then went back to sleep before beginning the morning direct-to-earth communication session with the high gain antenna.

At 10:00 a.m. Mars Local Solar time, Spirit began analyzing the soil targets "Saber" and "Sandbox" with the mini thermal emission spectrometer. It also took panoramic camera images of "Skull" and Saber. Then it was time to unfold the instrument arm to capture microscopic imager images of three targets on Mazatzal: "Arizona," "Illinois," and "New York." The New York target was further analyzed with a 17-hour Moessbauer spectrometer integration.

While the Moessbauer was integrating, Spirit proceeded to execute several mini thermal emission spectrometer and panoramic camera observations of interesting features in the surrounding area. The observations included images of "Bonneville" crater, "Saber," "Sandbox" and "Orange Beach."

Spirit had completed all these activities by 2:40 p.m. Mars Local Solar time and then took a siesta until the afternoon Odyssey UHF pass. During that pass, the rover captured mini thermal emission spectrometer ground and sky images. Before shutting down at 5 p.m. Mars Local Solar time, Spirit positioned the panoramic camera for a nighttime observation of the moon Deimos.

Sol 79, which ends at 1743 GMT on March 24, 2004, will be a momentous day for Spirit's rock abrasion tool; it will complete brushings on two Mazatzal targets.

TUESDAY, MARCH 23, 2004
Three weeks ago, NASA announced definitive evidence that Mars once featured an abundance of water supporting a habitable environment. But major questions remained. Today, scientists unveiled photographs from NASA's Opportunity rover showing cross-bedded sedimentary rocks indicating that at least at one point on the martian surface - Meridiani Planum - a shallow, salty sea once ebbed and flowed. Read our full story.

1904 GMT (2:04 p.m. EST)
NASA's Opportunity rover has demonstrated some rocks on Mars probably formed as deposits at the bottom of a body of gently flowing saltwater.

"We think Opportunity is parked on what was once the shoreline of a salty sea on Mars," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science payload on Opportunity and its twin Mars Exploration Rover, Spirit.

Clues gathered so far do not tell how long or how long ago liquid water covered the area. To gather more evidence, the rover's controllers plan to send Opportunity out across a plain toward a thicker exposure of rocks in the wall of a crater.

NASA's Associate Administrator for Space Science Dr. Ed Weiler said, "This dramatic confirmation of standing water in Mars' history builds on a progression of discoveries about that most Earthlike of alien planets. This result gives us impetus to expand our ambitious program of exploring Mars to learn whether microbes have ever lived there and, ultimately, whether we can."

"Bedding patterns in some finely layered rocks indicate the sand-sized grains of sediment that eventually bonded together were shaped into ripples by water at least five centimeters (two inches) deep, possibly much deeper, and flowing at a speed of 10 to 50 centimeters (four to 20 inches) per second," said Dr. John Grotzinger, rover science-team member from the Massachusetts Institute of Technology, Cambridge, Mass.

In telltale patterns, called crossbedding and festooning, some layers within a rock lie at angles to the main layers. Festooned layers have smile-shaped curves produced by shifting of the loose sediments' rippled shapes under a current of water.

"Ripples that formed in wind look different than ripples formed in water," Grotzinger said. "Some patterns seen in the outcrop that Opportunity has been examining might have resulted from wind, but others are reliable evidence of water flow," he said.

According to Grotzinger, the environment at the time the rocks were forming could have been a salt flat, or playa, sometimes covered by shallow water and sometimes dry. Such environments on Earth, either at the edge of oceans or in desert basins, can have currents of water that produce the type of ripples seen in the Mars rocks.

A second line of evidence, findings of chlorine and bromine in the rocks, also suggests this type of environment. Rover scientists presented some of that news three weeks ago as evidence the rocks had at least soaked in mineral-rich water, possibly underground water, after they formed. Increased assurance of the bromine findings strengthens the case rock-forming particles precipitated from surface water as salt concentrations climbed past saturation while water was evaporating.

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, "Many features on the surface of Mars that orbiting spacecraft have revealed to us in the past three decades look like signs of liquid water, but we have never before had this definitive class of evidence from the martian rocks themselves. We planned the Mars Exploration Rover Project to look for evidence like this, and it is succeeding better than we had any right to hope. Someday we must collect these rocks and bring them back to terrestrial laboratories to read their records for clues to the biological potential of Mars."

Squyres said, "The particular type of rock Opportunity is finding, with evaporite sediments from standing water, offers excellent capability for preserving evidence of any biochemical or biological material that may have been in the water."

Engineers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., expect Opportunity and Spirit to operate several months longer than the initial rover's three-month prime missions on Mars. To analyze hints of crossbedding, mission controllers programmed Opportunity to move its robotic arm more than 200 times in one day, taking 152 microscope pictures of layering in a rock called "Last Chance."

MONDAY, MARCH 22, 2004
2325 GMT (6:25 p.m. EST)
Opportunity successfully emerged from the crater today, one martian-day later than planned after the rover experienced wheel slippage in the sandy soil.

Controllers sent the rover driving along the crater rim instead of a more direct path straight out, officials said.

The crater, dubbed "Eagle Crater," is approximately 22 meters (72 feet) in diameter.

The twin rover Spirit continues to explore the Bonneville Crater. Here is the latest mission control staus report: Spirit woke up on sol 77, which ended at 1624 GMT today, to "One Step Closer" by the Doobie Brothers, since the rover was to make its final approach to the rock target named "Mazatzal" today.

Before beginning the .9-meter (2.95 feet) drive to Mazatzal, Spirit analyzed the soil target "Soil 1" at its current location with the microscopic imager and Moessbauer spectrometer. During the Moessbauer integration, Spirit also took panoramic camera images and performed miniature thermal emission spectrometer analysis of the atmosphere and Mazatzal work area.

At 1:25 p.m. Mars Local Solar Time, Spirit completed the Moessbauer integration, took a few microscopic imager images of the impression left on "Soil 1" by the Moessbauer spectrometer and then stowed the instrument arm. Spirit then proceeded the short distance toward Mazatzal and took hazard avoidance camera images to confirm that its final resting place put the intended rock targets in reach of the instrument arm.

Following the drive, the rover acquired more panoramic camera and mini thermal emission spectrometer observations of the atmosphere, and of interesting areas near the Mazatzal site including targets named "Sandbox," "Saber" and "Darksands."

Spirit finished up sol 77 by getting the mini thermal emission spectrometer in position for morning observations on sol 78.

Spirit will spend most of Sol 78, which will end at 1704 GMT Tuesday, analyzing Mazatzal with the instruments on the robotic arm.

1800 GMT (1:00 p.m. EST)
The Mars rover Opportunity has been unable to drive out of the bowl-shaped crater it has been exploring for nearly two months, prompting controllers to plot a new route. Meanwhile, NASA officials on Tuesday will announce a "major scientific finding" from Mars.

"NASA's Opportunity tried driving uphill out of its landing-site crater during its 56th sol, ending at 0605 GMT today, but slippage prevented success," mission control reported.

"The rover is healthy, and it later completed a turn to the right and a short drive along the crater's inner slope. Controllers plan to send it on a different route for exiting the crater on sol 57."

Opportunity scored an "interplanetary hole in one" when it landed in the small crater on January 25 after its seven-month voyage spanning 300 million miles from Earth to Mars.

The rover is studying the Meridiani Planum region of Mars where it recently discovered evidence rocks at the landing site have been altered by water.

Tuesday's NASA news conference will be held at the agency's headquarters in Washington. The briefing begins at 2 p.m. EST (1900 GMT) with opening remarks from NASA Administrator Sean O'Keefe.

Presenting the discovery will be:

• Dr. Ed Weiler, NASA's Associate Administrator, Office of Space Science
• Prof. Steve Squyres, Cornell University, Ithaca, N.Y., and MER Principal Investigator
• Prof. John Grotzinger, Massachusetts Institute of Technology, Cambridge, Mass, and a MER Co-investigator
• Dr. Dave Rubin, U.S. Geological Survey Sedimentologist at the Pacific Science Center in Santa Cruz, Calif.
• Dr. Jim Garvin, NASA Lead Scientist for Mars and the Moon, Office of Space Science, NASA Headquarters

SATURDAY, MARCH 20, 2004
This is the latest Opportunity status report as written by Mission Control for sol 54:

Opportunity flipped 115 meters (377.3 feet) on its odometer during the latest drives along the current soil survey campaign, surpassing the total drive distance of 1997's Sojourner rover. After performing a "touch and go" sequence at the third soil target south of the Challenger Memorial Station, Opportunity moved east to its fourth target. There the rover used its wheels to dig a trench that will be studied in coming sols.

The sol, which ended at 0246 GMT on March 20, started with brief alpha particle X-ray and Moessbauer spectrometer measurements on the soil target known as "Coconut2." These were followed by two sets of microscopic imager shots of Coconut2 and "ChocolateChip." The rover then stowed its arm and drove.

Remote sensing with the miniature thermal emission spectrometer and the panoramic camera remote sensing was performed before, during, and after the drive and trenching activities. Also, Opportunity took additional images with its navigation camera imaging in preparation for next sol's drive to the final site inside the crater.

To prepare for the trenching on this sol, the wake-up song was "I Feel The Earth Move" by Carole King.

FRIDAY, MARCH 19, 2004
This is the latest Spirit status report as written by Mission Control:

Spirit began the morning of Sol 74, which ended at 1425 GMT on March 19, by completing an alpha particle X-ray spectrometer integration on the target "Panda," inside the scuff on "Serpent" drift. Then Spirit placed the alpha particle X-ray spectrometer back down on the target "Polar" for a 30-minute integration. During that integration, Spirit took some images of disturbed soil with the panoramic camera, and acquired some ground temperatures with the miniature thermal emission spectrometer. Spirit then switched the tools on its robotic arm to the Moessbauer spectrometer for an hour-long integration on Polar. During that integration, the rover took some sky and ground measurements with the mini thermal emission spectrometer. Spirit finished its arm activities for the day by acquiring three microscopic images of Polar and three more of Panda.

Starting around 12:35 p.m. Mars Local Solar time, Spirit made a direct drive of about six meters (19.7 feet) to another section of the Serpent drift complex, called "Stub Toe." There the rover repeatedly scuffed the drift and advanced .15 meters (half a foot) in a series of five "scuff and drives." After the five scuffs and advances were made, Spirit roved forward another 3 meters (9.8 feet) and then looked back over its shoulder using the mini thermal emission spectrometer and navigation cameras to analyze the damage. The rover continued along the Bonneville crater rim with a 16-meter direct drive, and then an auto-navigation drive for 9 meters (29.5 feet). Spirit completed a final set of drives to set up for a touch and go on sol 75 at around 2:10 p.m. Mars Local Solar time. The total amount of driving for sol 74 was an impressive 34.3 meters (112.5 feet).

Spirit then took navigation camera and panoramic camera images of the drive directions for planning the sol 75 traverse. The rover acquired some mini thermal emission spectrometer reconnaissance images and then took a 30-minute siesta before the afternoon Odyssey relay pass. During that pass, Spirit used the mini thermal emission spectrometer to acquire a sky profile and ground temperature observations.

On sol 75, which will end at 1505 GMT on March 20, Spirit will place the microscopic imager on a soil target and drive about 22 meters (72.2 feet) around the Bonneville crater rim. Spirit will also conduct atmospheric observations with the mini thermal emission spectrometer and panoramic camera.

THURSDAY, MARCH 18, 2004
A major ingredient in small mineral spheres analyzed by NASA's Mars Exploration Rover Opportunity furthers understanding of past water at Opportunity's landing site and points to a way of determining whether the vast plains surrounding the site also have a wet history. Read the full story.

WEDNESDAY, MARCH 17, 2004
This is the latest Spirit status report as written by Mission Control:

Sol 72, which ended at 1306 GMT on March 17, was a day full of digging for NASA's Mars Exploration Rover Spirit. Spirit began the day taking panoramic camera and miniature thermal emission spectrometer observations of the drift dubbed "Serpent" before creating the "scuff" that would reveal the inside material at this location.

Then it was time to get into position. The rover drove about two-and-a-half meters (8.2 feet) to put the left front wheel up onto the drift. It then turned right and left five degrees to dig the left front wheel into the drift. When the "shimmy" was complete, Spirit backed 10 centimeters (3.9 inches) out of the hole. The digging and backing process was repeated four times to thoroughly scuff Serpent's side. Then Spirit backed up another meter (3.28 feet) to attain miniature thermal emission spectrometer, panoramic camera and navigation camera observations of the scuffed area. These observations will aid in in-situ target selection. To prepare for the upcoming in-situ work, Spirit drove forward 0.4 meters (1.3 feet) for additional imaging, and then drove forward a final 0.45 meters (1.5 feet) to put the scuff in the arm work volume.

Spirit spent the rest of the day obtaining navigation camera and panoramic camera observations of the intended drive direction around part of the crater rim. Spirit will do some work overnight, taking miniature thermal emission spectrometer thermal inertia and atmosphere measurements.

On sol 73, which will end at 1346 GMT on March 18, Spirit will conduct extensive microscopic imaging of sections of the drift, and run an overnight Moessbauer and alpha particle X-ray spectrometer integration.

TUESDAY, MARCH 16, 2004
The Mission Control status reports from today covering the activities of Opportunity and Spirit:

Opportunity reached the first of five targets in its current soil survey on the rover's 51st sol on Mars. The sol, which ended at 0047 GMT on March 17, began with a salute to the rover's intended target on the southern face of the crater it has been exploring since its early sols on Mars. "Song of the South" by Alabama was chosen to wake Opportunity for a busy sol that involved a 15-meter (49.2 feet) u-shaped drive toward the soil target.

Before the rover ventured away from the outcrop that has been the focus for most of its mission, alpha particle x-ray spectrometer observations were completed on the red rind dubbed "Shark's Tooth." The arm was stowed before Opportunity "scuffed" the rock "Carousel" with its front left wheel. Results of the experiment were imaged as Opportunity backed up and prepared to drive away from the outcrop.

Backing down toward the center of the crater and then arcing around the Challenger Memorial Station, Opportunity ultimately drove back up the slope to a position fairly close to the rim. On its way to the current soil target, the rover was also able to image the trench it dug on sol 23 from a different angle.

In the coming sols, Opportunity will use the instruments on its arm to examine all five soil targets identified for the soil survey.

Spirit began sol 71, which ended at 1226 GMT March 16, with a morning nap to re-charge after the record-breaking number of activities it accomplished on sol 70. After that, it was back to work. Spirit began by retracting the alpha particle X-ray spectrometer, closing the doors, and imaging the doors with the front hazard avoidance cameras to confirm that they were closed. Spirit then proceeded to observe a soil target with the microscopic imager, and it also used the panoramic camera to observe the magnets, do a sky survey and capture a dust devil movie.

Then it was time to drive. Spirit completed a 15-meter (49.2 feet) blind drive followed by a 3-meter (9.8 feet) auto-navigation drive around the south rim of "Bonneville" crater toward a drift named "Serpent." Once there, Spirit completed post-drive science observations and a miniature thermal emission spectrometer study of the atmosphere, ground and future drive direction.

Spirit's main objective on sol 72, which ends at 1306 GMT March 17, will be to disturb and analyze the material at Serpent. Spirit will drive over the dune and back up to an optimal observation position. It will then analyze the area with the panoramic camera and mini thermal emission spectrometer. Spirit will end the sol by driving back on top of the dune.

MONDAY, MARCH 15, 2004
The Mars Exploration Rover Spirit has returned a stunning panorama from the rim of Bonneville Crater. The 180-degree mosaic shows the crater's interior and surrounding terrain. The heat shield that protected Spirit during the fiery descent through the Martian atmosphere is seen sitting on the opposite side of the crater. Read full story.

Meanwhile, Opportunity has completed its 50th workday on Mars as the rover neared completion of the rock outcrop study.

"The rover arm, with the Alpha Particle X-ray Spectrometer at the ready, was placed on the rock called 'Shark's Tooth' for a 30-minute observation. The Microscopic Imager then took a series of pictures of the targets 'Enamel 1' and 'Lamination.' The focus then switched back to 'Shark's Tooth' for an examination by the Moessbauer Spectrometer," mission control reported.

"The sol also included many panoramic camera observations of targets with creative names like 'Patio Rug,' 'Anaconda Snake Den,' 'West Zen Garden' and 'Garter Snake.'

"The next sol calls for a final experiment at the outcrop called 'scuffing.' 'Scuffing' essentially turns one of the rover wheels into a tool to scrape a rock to help determine its hardness. The rock 'Carousel' will be scraped by Opportunity's front left wheel. After that experiment, the rover will begin its trans-crater traverse to five soil survey targets, the first of which will lead Opportunity up the sandy southern face of the crater."

SUNDAY, MARCH 14, 2004
Here is the latest update from mission control on the twin Mars Exploration Rovers:

NASA's Opportunity finished inspecting the "Berry Bowl" site and drove 10 meters (33 feet) toward a new target during its 48th sol on Mars, which ended at 2250 GMT Saturday.

The rover used all four tools on its arm during the morning, ending with a brushing by the rock abrasion tool, then post-brushing examinations with the microscope and alpha particle X-ray spectrometer. This closed out three sols of work at "Berry Bowl" to compare the composition of targets with and without groups of the BB-sized spherules believed to have formed while the local environment was wet.

Opportunity then stowed its arm and drove toward an area dubbed "Shoemaker's Patio" at the southwestern end of the outcrop the rover has been studying since it arrived on Mars. This informal name pays tribute to the late geologist Dr. Eugene Shoemaker of the U.S. Geological Survey. Opportunity's more specific target is a rock called "Shark's Tooth" at the near edge of the patio. The drive did not quite put that target within reach of the robot arm. Activities of the sol also included atmospheric observations with the panoramic camera and miniature thermal emission spectrometer, plus post-drive imaging with the navigation camera.

Mission controllers at JPL chose John Williams' "Jaws: Main Title and Fist Victim" as the wake-up song for sol 48.

During its 69th sol on Mars, ending at 1107 GMT Sunday, NASA's Spirit finished shooting frames with its panoramic camera for a full 360-degree color view of the surroundings visible from the crater rim where the rover is perched. Once the panorama frames are transmitted to Earth, scientists will use them and information from Spirit's miniature thermal emission spectrometer to assess the structures and composition of the crater interior and other surfaces in view.

Spirit did not move from its vantage point on the south rim of the crater nicknamed "Bonneville." An extra downlink session was added via relay by NASA's Mars Odyssey orbiter to accelerate getting the panoramic imaging data to Earth. The total amount of data received from Spirit during the sol through relays and direct-to-Earth transmission was 225 megabits.

In the martian afternoon, Spirit added a set of observations with the miniature thermal emission spectrometer in coordination with overhead passage of NASA's Mars Global Surveyor orbiter, which carries a similar spectrometer looking down. Events of the sol also included two camera sessions requested by engineers. The first was to get high-resolution images of Spirit's heat shield on the northern rim of "Bonneville." The other was to photograph wheel tracks to help rover mobility specialists assess slippage. For sol 69's wake-up music, the team spun John Lennon's "Watching the Wheels."

Plans for sol 70, ending at 1147 GMT Monday, feature more remote sensing from the rover's current location, before a drive along the rim begins on sol 71.

SATURDAY, MARCH 13, 2004
Spirit spent all of sol 68, which ended at 1028 GMT on March 13, at the "Bonneville" crater location. It began the morning operating the panoramic camera to acquire the first images of what will be a 360-degree shot of "Bonneville's" rim and basin, and the "Columbia Hills" to the southeast.

Spirit also moved the instrument deployment device, or rover arm, into position to acquire panoramic camera images of the magnets on the rock abrasion tool. It then placed the Moessbauer spectrometer on soil for a short integration after taking five microscopic imager images.

Around 13:35 Mars Local Solar time, one of Mars' moons, Deimos, passed in front of the sun. Scientists and rover controllers took this opportunity to image the moon's transit with the panoramic camera before completing mini thermal emission spectrometer observations of the crater interior.

Spirit's work isn't over though. The Moessbauer will continue analyzing the soil at "Bonneville's" rim through the night.

Sol 69, which will end at 1207 GMT on March 14, 2004, will also be a no-drive sol during which Spirit will acquire the second half of the 360-degree panoramic camera image of Bonneville. Spirit will also perform remote sensing of the inside of the crater and analyze soil targets with the Moessbauer and alpha particle x-ray spectrometer.

FRIDAY, MARCH 12, 2004
The Mission Control status reports from today covering the activities of Opportunity and Spirit:

On sol 47, which ended at 2210 GMT on Friday, March 12, Opportunity awoke to "No Particular Place to Go" by Chuck Berry in recognition of the stay at "Berry Bowl." Engineers also played "That's Amore" by Dean Martin in honor of the Phobos moon's transit across the sky.

Opportunity finished remnants of activities from the past sol's research at "Berry Bowl." The sol started with the hazard avoidance camera taking a picture of the "Berry Bowl" area as a context picture. The miniature thermal emission spectrometer then performed some "sky stares" of the atmosphere. At 11:30 Local Solar Time, the robotic arm started moving. It picked up the alpha particle X-ray spectrometer and moved to a new location nearby, then switched to the Moessbauer spectrometer. Both spectrometers are searching for clues about the chemical composition of the mysterious "blueberries."

Later, Opportunity took panoramic camera images of the suite magnet on the rover itself, which is collecting atmospheric dust samples to understand why the martian dust is so magnetic. The panoramic camera also took images of a target dubbed "Fool's Silver," which contains an interesting angular feature in the outcrop.

After all the morning's hard work, Opportunity took a short siesta to rest and recharge. Opportunity reawakened a few hours later to take more images of the atmosphere with the miniature thermal emission spectrometer and panoramic camera. Those were taken in the same locations as the morning measurements to compare the atmospheric data throughout the sol.

At 15:40 Local Solar Time, Opportunity took about a dozen images of the Sun to catch the eclipse by the martian moon, Phobos. Opportunity once again shut down for a nap and woke up at 4:53 Local Solar Time, sol 48, for a tool change and a communications session with the Odyssey orbiter. While the rover was awake for the Odyssey pass, the rover heated up the robotic arm, which had chilled to almost -80 degrees Celsius (-112 degrees Fahrenheit). The motors cannot move at that frigid temperature, so the rover arm heated for 32 minutes to surpass the operational temperature of 40 degrees Celsius (104 degrees Fahrenheit). As the rover arm quickly cooled, the heat lasted long enough (5 minutes) for the arm to twist its wrist and change instruments from the Moessbauer spectrometer back to the alpha particle X-ray spectrometer.

The rest of the plan for sol 48, which will end at 2249 GMT on Saturday, March 13, is to perform quite a few complicated maneuvers. Opportunity plans to brush an area with the rock abrasion tool, analyze the brushed area with the spectrometers, then drive 10 meters (33 feet) along the slippery slopes of the outcrop to "Shark's Tooth" in "Shoemaker's Patio."

Spirit woke up on sol 67, which ended at 0948 GMT March 12, 2004, to "On Top of the World" by the Carpenters. The song was fitting, as yestersols's drive put Spirit at the rim of "Bonneville" crater, but it took some additional maneuvering to get the rover perfectly placed for the 360-degree panoramic camera images it will take on upcoming sols.

Before beginning the sol 67 drive, Spirit completed an overnight alpha particle x-ray spectrometer integration and a couple of small panoramic camera shots of its surroundings.

Then the rover traveled 13 meters (42.7 feet) in a direct drive around some obstacles followed by a 1.4-meter (4.6 feet) automatic navigation drive. Spirit spent the afternoon using the mini thermal emission spectrometer to look at targets that will be analyzed more fully on sol 67, and then driving 0.9 meters (3 feet) forward to be able to access that area with the arm tomorrow.

Spirit put a total of 24.8 meters (81.4 feet) on the odometer today, partly due to some back and forth maneuvering it had to do to ensure a safe path. The final location has proven to be just right, and Spirit will stay put for a couple sols while it continues to investigate "Bonneville" crater.

Before the day was over, Spirit looked at the sun for an attitude update and then took front hazard avoidance camera images of the arm work volume, and a small navigation panorama of the crater. The rover also completed some mini thermal emission spectrometer analysis of the far side of the crater and finished the day with some panoramic camera images of the sunset.

On sol 68, which will end at 1028 GMT March 13, 2004, Spirit will begin a two-sol panoramic camera session and complete selected mini thermal emission spectrometer observations. The rover will also begin a very long Moessbauer integration on a soil target.

THURSDAY, MARCH 11, 2004
NASA's Spirit has begun looking down into a crater it has been approaching for several weeks, providing a view of what's below the surrounding surface. Read full story.

WEDNESDAY, MARCH 10, 2004
The Spirit rover has nearly reached its long-sought destination -- Bonneville Crater. On Tuesday, the craft conducted the longest directed drive to date.

"That drive was 27 meters (88.6 feet) toward the edge of Bonneville Crater," controllers said. "Spirit then attempted to use auto navigation to reach a target that was an additional 6 meters (19.7 feet) away. Sensitive obstacle avoidance software prevented Spirit from reaching the destination, and like yestersol, the rover completed several drives forward and back. Those drives resulted in a final odometer reading of 40.7 meters (133.5 feet) for the day, even though the total straight-line distance traveled was 30 meters (98.4 feet)."

Spirit has moved close enough to Bonneville's edge to take images with the navigation cameras that reveal the opposite rim of the crater, NASA reported.

The plan for Wednesday's workday, ending late this evening U.S. time, calls for Spirit to drive up to the summit of the rim and show us what's inside with a 180-degree navigation camera panorama.

Passing the halfway mark of its primary mission, the Mars rover Opportunity on Wednesday used the bristles of its Rock Abrasion Tool to brush away dirt inside and around the hole carved into the bedrock outcropping a day earlier.

Opportunity then snapped five microscopic images of the freshly brushed hole dubbed "Mojo 2," controllers reported.

"The Miniature Thermal Emission Spectrometer took measurements at three locations on the surface of Mars, and then pointed upwards to observe the atmosphere in four different directions. The panoramic camera was also busy taking images of the magnets around the Rock Abrasion Tool area, 'Mojo 2' post brushing, and a new area called 'Slick Rock,'" NASA said.

NASA will hold this week's rover status and science news conference on Thursday at 1 p.m. EST (1700 GMT).

TUESDAY, MARCH 9, 2004
After its earlier attempt stalled, Opportunity has successfully used the Rock Abrasion Tool to grind a 3.1 millimeter-deep (just over one-tenth of an inch) hole in the "Mojo 2" target on "Flatrock." The cutting occurred early Tuesday (U.S. time) -- the rover's 44th workday on Mars.

"Yesterday, diagnostic testing determined a voltage adjustment was necessary to overcome some mechanism 'stickiness' in the routine during which the Rock Abrasion Tool finds the highest point in the target area," NASA reported.

"The routine worked perfectly on this grind with the new voltage setting. After one hour and five minutes of successful grinding, the Rock Abrasion Tool grind motor stalled, probably while grinding into one of the spherules also known as 'blueberries.' These objects are known to obstruct the grinding tool and cause it to terminate its sequence."

The Mossbauer Spectrometer was placed on the freshly-cut rock hole Tuesday, followed later by the Alpha Particle X-ray Spectrometer.

Meanwhile, the Miniature Thermal Emission Spectrometer took two long atmospheric measurements and the panoramic camera was busy taking images of the RAT hole and surrounding target areas, controllers said.

Twin rover Spirit remains on the move, surpassing the 300-meter mark Monday night (U.S. time).

"Spirit completed another 29 meters (94 feet) of its drive toward the rim of Bonneville Crater on sol 64, which ended at 11:49 p.m. PST, bringing its total odometry to 314 meters (1,030 feet) -- 14 meters (45.9 feet) past the minimum mission success criterion," NASA said.

"Spirit began the morning with an 18-meter (59 feet) direct drive that safely maneuvered the rover through a field of rocks. Spirit then traversed 11 more meters (35 feet) using autonomous navigation and at 11:30 a.m. Mars Local Solar Time completed the drive. Spirit had some difficulty finding a way around an obstacle during the last portion of the commanded drive. That resulted in some repeated forward and backward maneuvering which left an interesting 'trench' for scientists to have the rover peer into.

"Spirit is climbing up a very steep part of Bonneville now, and ended this sol's drive tilted at a forward pitch of about 15 degrees."

MONDAY, MARCH 8, 2004
Engineers believe they have determined why the rover Opportunity was unable to grind into the rock outcrop Sunday morning as planned.

"Using a combination of microscopic images, hazard avoidance camera images, and Rock Abrasion Tool tests on sol 43 (Monday), Opportunity's engineering team discovered that the grind motor of the Rock Abrasion Tool on Mars stalled prematurely during what's called the 'seek/scan' phase when the Rock Abrasion Tool instrument searches for the rock face. This resulted in no contact during the actual grind activity on sol 42 (Sunday).

"The most likely causes of the stall are dust and dirt accumulations and temperature variations on the instrument. The tests also confirmed that engineers can safely increase the motor voltage on the instrument to prevent a future stall."

The grinding has been rescheduled for Tuesday.

SUNDAY, MARCH 7, 2004
The Opportunity rover's Rock Abrasion Tool failed to grind a hole into the so-called "Flat Rock" area of the bedrock outcropping on Sunday morning.

Mission control said the operation "produced almost no discernable impression on the rock."

Controllers plan to run diagnostic tests early Monday "to aid with tuning parameters for a second grinding attempt."

"All indications are that the tool is healthy," NASA said.

Spirit continues cruising to Bonneville Crater, driving 26.15 meters (85.8 feet) on Saturday.

"Some of the drive maneuvered around obstacles. The net gain in the northeasterly direction toward the crater rim was 22 meters (72 feet), and that destination was estimated to be about 88 meters (289 feet) away from Spirit's new location," NASA reported.

That puts Spirit's odometer at 250.71 meters (822.5 feet).

SATURDAY, MARCH 6, 2004
The Spirit rover resumed driving Friday, leaving the "Middle Ground" area that it had explored for a week.

"In the Martian morning, Spirit's panoramic camera took the final frames needed for the camera team to assemble a full-circle color panorama after all the data reaches Earth," mission control reported.

"In the early afternoon, Spirit backed up 0.5 meter (20 inches), then edged forward 0.29 meters (11 inches) to sidestep a rock called 'Ingrid.' Then the rover advanced 28.5 meters (94 feet) toward its crater-rim destination. The drive took 45 minutes. From the new location, Spirit took forward-looking pictures for use in future drive planning. It also observed the ground and the sky with its Miniature Thermal Emission Spectrometer."

Spirit was scheduled to continue driving on its Saturday workday, which is known as sol 62.

Opportunity spent the overnight hours of Friday morning finishing an Alpha Particle X-ray Spectrometer observation at the "Last Chance" area of the rock outcrop and completed a morning set of panoramic camera and Mini-TES remote sensing observations.

"At 11:30 Local Solar Time, engineers retracted the Alpha Particle X-ray Spectrometer off the target, took a final set of 24 microscopic images, and stowed the arm for driving," controllers reported.

"Opportunity then scored another first by successfully using visual odometry to navigate autonomously on Mars. During a drive along the crater wall, the vehicle properly identified wheel slippage on the steep slope of the crater wall using features in the navigation camera imagery. This effectively provided a mid-course correction that landed the science and engineering team exactly at the target location where they want Opportunity to do work using the instruments on the rover arm on sol 41 (Saturday)."

Operating half-a-world away from Spirit, Opportunity's Saturday workday has been completed. The rover inspected a rock area called "Wave Ripple" with the arm, then drove to a new target dubbed "Flat Rock" near the south end of the outcrop that the rover has been examining for weeks, officials said.

"Although the rover wheels slip some in the local soil and the drive traversed a slope of 10 to 11 percent, Opportunity and engineers at JPL navigated the trip so well that a planned final approach to the target on sol 42 (Sunday) could be cancelled. The target is within the work volume of Opportunity's robotic arm.

"The drive was done in a series of one-meter (3.3-foot) segments making up a U-shaped path to the south and west. Each segment included a correction for slippage.

"Before starting the drive, Opportunity used its microscope for 50 images of 'Wave Ripple,' and examined the composition of the rock with its Alpha Proton X-ray Spectrometer and its Mossbauer Spectrometer."

THURSDAY, MARCH 4, 2004
The Mars Exploration Rover Spirit is completing its study of a rock named Humphrey, which had a small depression carved into it.

The planned four-hour Rock Abrasion Tool grind of Humphrey on Tuesday was cut short to only 20 minutes.

"The intricate slopes and cracks of the rock make it a challenging target for instruments. When sensors indicated a loss of contact with surface material, the software perceived a problem and the Rock Abrasion Tool was moved away from the rock," mission controllers reported.

"Engineers identified the software issue that caused the Rock Abrasion Tool to terminate its original planned grinding on sol 58. The minor bug will be fixed when new flight software is loaded at the end of March."

On Wednesday, Spirit successfully completed a two millimeter-deep grind (.08 inches) carve. A five-minute brush to clean the hole followed. The suite of science instruments then went to work studying the shallow cut.

The rover backed up 0.85 meters (about 2.8 feet) on Thursday, allowing the Miniature Thermal Emission Spectrometer and panoramic camera to observe Humphrey's RAT hole and previously brushed areas.

Meanwhile on Opportunity, the rover drove 4.25 meters (14 feet) Tuesday to the "Last Chance" area of the rock outcrop.

"With the moves of a tango dancer, the drive was another intricate study in, and challenge of, driving on a slippery, steep slope," mission control said.

"The rover was directed to: turn right, go forward, turn right, take images of 'Last Chance,' turn right, go forward, turn left, go forward, turn right, take images of 'Big Bend,' go straight, turn left and go straight! Due to the challenges of driving and pirouetting on such a steep slope (as steep as 22 degrees) the rover found it difficult to maintain a perfectly straight course, and Opportunity came up shy and right of the 'Last Chance' target by about 30 centimeters (about one foot)."

Wednesday saw the rover observe the atmosphere with the panoramic camera and Miniature Thermal Emission Spectrometer. Then, Mini-TES was used to stare at the ground for science observations. After making stereo microscopic images and Mossbauer Spectrometer readings of the soil target dubbed "Pay Dirt," Opportunity stowed its arm, took a panoramic camera image of "Last Chance," and drove a very short distance of 0.4 meters (16 inches) toward "Last Chance" to prepare for the deployment of the robotic arm.

On Thursday, put its arm through an extraordinary workout.

"The science and engineering team built a whopping 490 commands to accomplish the most complex robotic arm operations on Mars yet. Opportunity took three mosaics on the area dubbed 'Last Chance,' using the microscopic imager, creating 128 images in over 200 arm moves. Each 'frame' of these mosaics required multiple microscopic images," controllers reported.

"There are two reasons for this. First, the microscopic imager does not have auto-focus, so the team needed to have Opportunity take and return multiple images at each location at different distances from the rock to get at least one in focus. A second reason is that the team needed Opportunity to take an extra image at a slightly different angle for each frame to create the right conditions to build stereo and computer-generated graphics of the 'topography' of the rock area up close.

"After about two-and-a-half hours of microscopic imager maneuvers, the robotic arm placed the Mossbauer spectrometer on a location at 'Last Chance' called 'Makar.' Opportunity also used the panoramic camera to watch the rare solar crossing of the sun by the moon Diemos and took images of the sky in coordination with the European Space Agency's orbiter at Mars, Mars Express."

TUESDAY, MARCH 2, 2004
NASA's Opportunity rover, studying exposed bedrock in the crater where it landed by chance in January, has found clear evidence that Mars once supported a wet, habitable environment, one that would have been suitable for life, scientists announced today. Read our full story.

1907 GMT (2:07 p.m. EST)
Scientists have concluded the part of Mars that NASA's Opportunity rover is exploring was soaking wet in the past.

Evidence the rover found in a rock outcrop led scientists to the conclusion. Clues from the rocks' composition, such as the presence of sulfates, and the rocks' physical appearance, such as niches where crystals grew, helped make the case for a watery history.

"Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. "We've been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion."

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, "NASA launched the Mars Exploration Rover mission specifically to check whether at least one part of Mars ever had a persistently wet environment that could possibly have been hospitable to life. Today we have strong evidence for an exciting answer: Yes."

Opportunity has more work ahead. It will try to determine whether, besides being exposed to water after they formed, the rocks may have originally been laid down by minerals precipitating out of solution at the bottom of a salty lake or sea.

The first views Opportunity sent of its landing site in Mars' Meridiani Planum region five weeks ago delighted researchers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., because of the good fortune to have the spacecraft arrive next to an exposed slice of bedrock on the inner slope of a small crater.

The robotic field geologist has spent most of the past three weeks surveying the whole outcrop, and then turning back for close-up inspection of selected portions. The rover found a very high concentration of sulfur in the outcrop with its alpha particle X-ray spectrometer, which identifies chemical elements in a sample. "The chemical form of this sulfur appears to be in magnesium, iron or other sulfate salts," said Dr. Benton Clark of Lockheed Martin Space Systems, Denver. "Elements that can form chloride or even bromide salts have also been detected."

At the same location, the rover's Moessbauer spectrometer, which identifies iron-bearing minerals, detected a hydrated iron sulfate mineral called jarosite. Germany provided both the alpha particle X- ray spectrometer and the Moessbauer spectrometer. Opportunity's miniature thermal emission spectrometer has also provided evidence for sulfates.

On Earth, rocks with as much salt as this Mars rock either have formed in water or, after formation, have been highly altered by long exposures to water. Jarosite may point to the rock's wet history having been in an acidic lake or an acidic hot springs environment.

The water evidence from the rocks' physical appearance comes in at least three categories, said Dr. John Grotzinger, sedimentary geologist from the Massachusetts Institute of Technology, Cambridge: indentations called "vugs," spherules and crossbedding.

Pictures from the rover's panoramic camera and microscopic imager reveal the target rock, dubbed "El Capitan," is thoroughly pocked with indentations about a centimeter (0.4 inch) long and one-fourth or less that wide, with apparently random orientations. This distinctive texture is familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. When the crystals later disappear, either by erosion or by dissolving in less-salty water, the voids left behind are called vugs, and in this case they conform to the geometry of possible former evaporite minerals.

Round particles the size of BBs are embedded in the outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity's observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins.

Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges.

The images obtained to date are not adequate for a definitive answer. So scientists plan to maneuver Opportunity closer to the features for a better look. "We have tantalizing clues, and we're planning to evaluate this possibility in the near future," Grotzinger said.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington.

1903 GMT (2:03 p.m. EST)
The rover Opportunity has proved that liquid water once "drenched" the surface at its landing site on Mars, NASA space science chief Ed Weiler is announcing at a news conference underway.

Confirming that the planet had water is a "giant leap" in determining if Mars once had life, Weiler says.

MONDAY, MARCH 1, 2004
While scientists and officials prepare for Tuesday's announcement regarding "significant findings" from Opportunity, the rover spent its workday completing an Alpha Particle X-ray Spectrometer measurement on Guadalupe. The rover then performed a series of backward drives to move away from the "El Capitan" site in the outcrop.

See an image from the rover as it backed away from the outcrop.

"The rover also got in some remote sensing, including Miniature Thermal Emission Spectrometer observations and panoramic camera imaging of the holes created by the Rock Abrasion Tool. In addition, the panoramic camera took images of a crater to the east," Mission Control said.

On the upcoming workday (Monday night/Tuesday morning U.S. time), Opportunity will take several short drives in the direction of the "Last Chance" target in the "Big Bend" area of the outcrop, NASA said.

Meanwhile on Spirit, the rover made a .55-meter (1.8 feet) re-approach to "Humphrey" on Sunday to get into position for grinding with the Rock Abrasion Tool. After the repositioning, the rover took panoramic camera and Mini-TES data of its rear tracks and the path in front of it, leading the way to Bonneville Crater.

See the three brush marks here.

Today, Spirit observed the area on Humphrey that was brushed by the Rock Abrasion Tool. An area just to the right of the brushed area, where the RAT will grind into the rock, was also examined, NASA reported.

"The morning hours found Spirit using its Alpha Particle X-ray Spectrometer on the intended grinding target to verify its similarity to the pre-brushed areas of the rock. The arm then switched out tools to the Microscopic Imager to get close-up views of the grinding target and the area to the right of it. The Mossbauer Spectrometer was then placed on the brushed area for another observation.

"Panoramic camera images were taken of the Rock Abrasion Tool magnets to study dust accumulation. The Miniature Thermal Emission Spectrometer performed a diurnal characterization on the nearby soil. This allows scientists to look at the temperature difference from day to night, revealing information about particle sizes within the soil."

Controllers now expect Spirit to carve into Humphrey on Tuesday.

SUNDAY, FEBRUARY 29, 2004
Spirit gave the rock nicknamed "Humphrey" a good brushing on Saturday. Using the wire-bristled brush of the Rock Abrasion Tool, the rover cleared the dust off three patches on the rock.

"Brushing three different places on a rock one right after another was an unprecedented use of the Rock Abrasion Tool, designed to provide a larger cleaned area for examining," NASA reported.

"Afterwards, Spirit rolled backward 85 centimeters (2.8 feet) to a position from which it could use its Miniature Thermal Emission Spectrometer on the cleaned areas for assessing what minerals are present. Due to caution about potential hazards while re-approaching Humphrey, the rover moved only part of the way back."

Controllers hoped to finish the move and additional inspections of the brushed area today. The Rock Abrasion Tool could be used to grind into Humphrey on Monday.

Meanwhile on Opportunity, the rover used its Microscopic Imager for eight observations of the fine textures of an outcrop-rock target called "Guadalupe" on Saturday night.

"The observations include frames to be used for developing stereo and color views," scientists said.

"Opportunity also used its Mossbauer Spectrometer and, after an overnight switch, its Alpha Particle X-ray Spectrometer to assess the composition of the interior material of Guadalupe exposed yestersol by a grinding session with the Rock Abrasion Tool."

Once finished with the close-up inspection of Guadalupe, Opportunity will back up to give the panoramic camera and Miniature Thermal Emission Spectrometer good views of the area where the rock interior has been exposed by grinding, officials said.

SATURDAY, FEBRUARY 28, 2004
Having completed its investigations at the first Rock Abrasion Tool grinding patch on the rock outcrop, the Mars rover Opportunity has moved slightly to reach the area dubbed "Guadalupe." On Friday night (U.S. time), the RAT was used to grind a tiny hole in this latest rock target.

"The rover looked at the patch with its microscope both before and after the grinding session. Then it placed its Mossbauer Spectrometer against the newly exposed interior material of the rock for a long reading of data that scientists use to identify what iron-containing minerals are present in the target," NASA reported.

"Opportunity also used its Miniature Thermal Emission Spectrometer during the sol to assess the composition of an outcrop feature dubbed 'Shoemaker Wall.' It took images of 'Guadalupe' with its panoramic camera before and after the use of the Rock Abrasion Tool.'"

On Saturday evening, Opportunity was scheduled to continue using its tools on the robotic arm to examine the rock interior exposed by the "Guadalupe" grind.

Meanwhile, Spirit approached a rock called "Humphrey" on Friday.

"The initial 3.5 meter (11.5 feet) drive toward the rock was cut short at only 2.5 meters (8.2 feet) due to a built-in software safety. Rover engineers quickly adjusted the software restriction and drove the final meter of that planned drive, plus the 0.9 meters (about 3 feet) that put the rover in the best position for brushing 'Humphrey' with the rock abrasion tool," NASA said.

"Before approaching the rock, Spirit used its Alpha Particle X-ray Spectrometer to investigate the areas the Rock Abrasion Tool will brush and grind.

"Unlike the last rock abrasion tool sequence on the rock called 'Adirondack,' the planned procedure for 'Humphrey' will include brushing three separate areas of the rock. After brushing, Spirit will back up and examine the brushed areas with the instruments on its arm. The science team will then decide the best place to grind into 'Humphrey' - it could be one of the three brushed areas or another section altogether. The hope is to remove as much dust as possible so the instruments on Spirit's arm can get a pre-grinding 'read' on the rock coating and then, after grinding, study beneath the coating and surface.

Once the RAT'ing and science collection is completed on Humphrey, Spirit will either "investigate an interesting rock behind it, or continue on toward Bonneville Crater."

Read our earlier Mission Status Center coverage.