Astronomy Picture of the Day 02-02-04

Thousands of files deleted on Spirit to fix computer trouble
BY SPACEFLIGHT NOW
Posted: February 1, 2004

A week-and-a-half after falling ill to computer woes, NASA on Sunday declared its Mars Exploration Rover Spirit was healthy again.

Mark Adler, rover mission manager. Credit: NASA/Bill Ingalls

"We have confirmed that Spirit is booting up normally. Tomorrow we'll be doing some preventive maintenance," mission manager Mark Adler reported Sunday.

Controllers worked to fix the computer ailment afflicting Spirit by purging thousands of data files from its flash memory. The no-longer-needed files piled up on the rover and prevented its computer system from successfully accessing the flash memory, triggering Spirit's computer to reset itself over and over again.

The flash memory stores engineering and scientific data even when the power is turned off, similar to electronic products like digital cameras.

Many of the tossed files were left over from the spacecraft's cruise to Mars.

A scan of the flash memory was performed late last week, providing engineers important diagnostic information, Adler said.

"We are now able to tell that when we mount the flash memory, it does in fact take a lot of the system RAM in the process. In fact, more system RAM than is available. So that's helping confirm the theory we had that the reason the restarts were hanging up was because we were running out of memory when we are trying to mount the flash memory," he explained during a news conference Friday.

Contact with Spirit was lost after the trouble began on Wednesday, January 21. Wrestling to regain control of the craft, engineers developed a plan to put the rover into a "cripple" operating mode that didn't use the flash memory.

With the file deletions completed, Spirit's computer has been "stable" while working in the standard mode with access to the flash memory.

"To be safe, we want to reformat the flash and start again with a clean slate," Adler said Sunday.

Monday's reformatting will erase everything stored in the flash file system and install a clean version of the flight software.

In preparation for that reformatting, Spirit was expected on Sunday to transmit priority data remaining in the flash memory. The information included data from atmospheric observations made in mid-January when the European Space Agency's Mars Express orbiter flew overhead.

Engineers say the flash may need to be reformatted every one-to-two weeks to prevent further trouble. Similar measures are likely for sister-rover Opportunity.

In the upcoming days, Spirit will finish the study of its first rock, nicknamed Adirondack. The Rock Abrasion Tool will be used to scrub off the rock's surface to give the science instruments a window into Adirondack's interior.

This close-up look at Adirondack was captured by Spirit's microscopic imager before Spirit. This is the first-ever microscopic image of a rock on another planet. Credit: NASA/JPL/US Geological Survey

Spirit's Mossbauer Spectrometer made readings of the pyramid-shaped, football-sized rock's composition and the microscopic imager snapped extremely close-up views prior to the computer problems. That data was finally transmitted to Earth late last week.

"If you had a hammer and whacked that rock, it would ring," said Ray Arvidson, rover deputy principal investigator.

Adirondack is a hard, crystalline rock that contains olivine, pyroxene and magnetite minerals. Researchers say that composition is common in Earth's volcanic basalt rocks. It isn't the proof of past water on Mars that the rovers were sent to find.

"Adirondack seems to be a good, hard volcanic rock," Arvidson said. "That suggests to us that we may be looking at material either excavated from below by craters, or broken out lava flows or transported in. It's not the kind of smoking gun evidence that we are looking for in terms of climatic history."

Two of Spirit's potential target rocks, which are near the rock called Adirondack, are seen here. The rock on the left has been named "Cake," and the white rock on the right has been named "Blanco." Image Credit: NASA/JPL/Cornell

Next, Spirit will drive to a nearby light-colored rock for study. Future plans call for the rover to head toward a crater, nicknamed Bonneville, about 820 feet away to study rocks thrown outward by the crater-forming impact.

"I suspect what we will do is take a look at some of these so-called white rocks that might be dusted basaltic rocks. If they don't look interesting, as quickly as possible do a traverse up to Bonneville Crater," Arvidson said.

Nearing the one-month mark of its planned three-month mission on Mars, Spirit is just beginning its science work. Officials are quick to point out the rover's wheels won't fall off when the 90-day primary mission period ends, giving hope that the craft will continue to explore in an extended life.

"We have gone through a third of our warranty, I guess, on the mission. But we think we have quite a few more months to go. I expect once we get the vehicle back in operation we will make pretty rapid progress in getting through the science objectives that we have in sight," Adler told reporters.

Opportunity finds what it went to Mars looking for
BY SPACEFLIGHT NOW
Posted: February 1, 2004

With the pop of a champagne cork, a scientist announced Saturday that the Mars rover Opportunity has found scattered across the landing site a mineral that typically forms in water.

NASA's Mars exploration program is dedicated to finding evidence of past water on the Red Planet and eventually determining if life ever existed on Earth's cosmic neighbor.

In the days before driving off its lander, Opportunity used its infrared-sensing instrument, called the Miniature-Thermal Emission Spectrometer, or Mini-TES, to paint a picture of the landing site's mineral composition. The device is similar to one flown aboard the orbiting Mars Global Surveyor, which discovered the presence of hematite on the plains of Meridiani, prompting scientists to send the rover there for up-close examination.

"As you all know, we came to Meridiani in search of a particular mineral called hematite," Phil Christensen, spectrometer lead scientist, said at a news conference Saturday. "The hematite was discovered from an orbiting spectrometer looking down from Mars Global Surveyor. One of the first questions we wanted to answer when we got here on the surface was did we really find this hematite? And I'm here today to say that Mini-TES has indeed discovered hematite on the surface of Mars."

This spectrum captured by the Mars Exploration Rover Opportunity's Mini-Thermal Emission Spectrometer shows the presence of hematite in the soil at Meridiani Planum. Credit: NASA/JPL/Arizona State University

The proof is a squiggly line on a data graph. A laboratory spectrum of hematite, shown as the red curve, matches with the Mini-TES spectrum of the dark soil near the lander, shown as the yellow curve. Scientists say the W-shaped feature in the lines on the right indicates the hematite discovery.

Opportunity landed inside a crater 72 feet in diameter and 10 feet deep. The crater's gray soil granules have the hematite. But a portion of the crater's wall that has exposed bedrock, a white tabular outcrop, doesn't contain hematite.

"We have looked with Mini-TES at the white bedrock. One of our goals is to see what it is made of. All I can say at the moment is what it's not...That white unit does not have hematite in it," Christensen said.

Opportunity's arrival on Mars was shrouded by impact-cushioning airbags. After coming to rest inside the small crater, the bags deflated and the lander base opened its petals like a flower to reveal the rover packed inside. That wild ride of a landing disturbed the terrain, causing some areas of hematite on the dark Martian surface to seemingly disappear where the airbags hit the ground, exposing brighter red subsoil.

"Just next to the bounce marks we see a beautiful signature of hematite. In the bounce marks itself we do not see hematite. So this beautiful rover has already performed its first experiment before it even opened its petals. The airbags actually altered the surface enough so that it appears the hematite is carried in the coarse material and the fine red material underneath it we do not see this hematite signature.

"I think we are going to have a lot of fun exploring exactly where the hematite is," Christensen said.

The "footprints" left by Opportunity's landing airbags are creating curious questions in the hematite search. Credit: NASA/JPL
Download larger image

Researchers are split in the debate of where the hematite went. Some think the gray granules were pushed beneath the surface's fine red material, others believe the hematite was pulverized.

But what does the disappearance tell scientists?

"I have lots of guesses. I'm sure they are all wrong. I'll share them anyway. That's the beauty of exploration that we are trying to find these answers," Christensen quipped.

"One of my worst fears was that the hematite was in the dust, this fine grain material, and it was everywhere and we would have a hard time tracking down the source. And without its source we would have a hard time tracking down its origin. It was extremely exciting and satisfying to see it in this coarse grain material as opposed to being in this fine grain sort of dust beneath that.

"I believe that the source of the material is in the rock unit that once lived on top of this white bedrock. And that is consistent with it being in this coarse grain material. Now, we can trace that material back to where it started and hopefully find its origin. Once we see it in place in its natural state, I think we'll have a much better clue of where it came from. Being in that coarse material is a huge first step at unraveling this mystery."

This high-resolution image captured by the Mars Exploration Rover Opportunity's panoramic camera highlights the puzzling rock outcropping that scientists are eagerly planning to investigate. Credit: NASA/JPL/Cornell
Download full image

How the hematite formed is another important question without an answer.

"The spectrum we see of hematite is distinctive between one of two origins -- a low temperature origin and a high temperature origin. From the data we have so far, it matches best to a low temperature origin," Christensen said.

On Earth, the mineral originates in various water, hydrothermal and volcanic situations.

Opportunity's science arm carries Mossbauer Spectrometer and Alpha Particle X-ray Spectrometer instruments to determine the composition of soil and rock samples. The arm will be placed on the hematite-bearing gray granules to determine what else is contained within.

Scientists hope to uncover other clues in the soil that will lend proof to a water origin theory or a volcanic one.

After completing its study of the soil and rock outcrop inside the landing crater, the robot geologist Opportunity will drive onto the smooth, flat plains of Meridiani.

"The view we see from orbit says this entire area is blanketed with hematite. It looked for the most part from orbit like it's not a wind blown material; it didn't come from a long way from somewhere else. The inference is there's a rock layer sitting on top of this white bed. As we get out of this crater that we're in, I think we will get up on a surface that is rich in hematite and we'll track it down."

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.