Around the Hills in 90 Sols

Pasadena, Sol 81 Spirit Rover

After nearly three months working on Mars’ time, a trimmed down engineering team plans to service the rovers’ daily operation with a more terrestrial turn. According to Matt Wallace, a JPL mission manager, the staff likely to realize the benefits will be about three-quarters of what has manned the consoles round-the-clock since January: "Next week, we transition off Mars’ time. It has been a trying schedule." Because days on Mars are approximately 40 minutes longer than Earth’s, a constantly rotating circadian rhythm has posed an irregular sleep and work period for the last three months. "As we move to an extended mission schedule (beyond the 90 days on the surface that were nominal) a new 7 AM to 10 PM period will ease the pain on a hardworking team without losing mission capability."

Ejecta and rocks strewn around Bonneville crater show signs of wind weathering. A wind-streaked bright rock called Mazatzal has caught geologists attention.
Image Credit: NASA/JPL


The next few weeks will involve a new flight software uplink, as both vehicles spend time around the rims of craters. If a theme has developed in addition to ‘follow the water’, it might be use these craters as natural excavations. A prime goal has been to find vertical reliefs that might tell more of Mars’ layered history.

The Spirit rover spent most of its week around Bonneville crater, followed by driving days of thirty meters to a scalloped rock called Mazatzal. The rock stood out in panoramic view because it is much lighter than its surrounding debris, some of which was ejected from the crater. But Mazatzal, according to Deputy Principal Investigator, Dr. Ray Arvidson, has a wind-scoured history. "This is a rock shaped by wind. It flutes were shaped by wind coming off the rim of Bonneville crater. We want to know, it is this light color all the way through?"

The Spirit rover began drilling Mazatzal on sol 83, its 83rd day operating on the surface. After first brushing the light dusty coating revealed a dark rock underneath, geologist went deeper than ever before. They holed out a deep eight millimeter section to get to what may be the original material. By profiling the vertical slice, scientists hope to understand the current conditions and weathering environment.

Arvidson divided the Spirit mission into three phases, some of which have completed and others which will soon commence: "We want to get good maps of the Columbia Hills" — an uplifted region inside the larger Gusev crater. The mission team has adopted the term traverse science to describe how it breaks up extended driving times. Typically these commands involve taking a panoramic and microscopic images so that nothing interesting is missed on the way to a distant target, much like a tourist stops for a progress photograph to mark steps on a map. "The rover has three parts, looking at Bonneville ejecta, doing traverse science, and a fast drive to the Columbia Hills, an older piece of the martian crust."

Arvidson noted that they ultimately want to test if the Gusev region was a lake before volcanic flows filled in the top layer of soil and rocks that the rover sees today.

Columbia Hills are important, "as an island of older rock that was uplifted from surrouding areas. They are 2.4 kilometers (1.3 miles) away." Scientists who hoped that the Bonneville crater would reveal such bedrock discovered that its ejecta was volcanic or basaltic. "The ejecta from Bonneville is basaltic, so the impact did not excavate deep enough," noted Arvidson, referring to the long-term hope of finding something closer to the lakebed.

"Columbia Hills look different, with vague striations relative to the horizontal," said Arvidson. "They may have ejecta from Gusev itself. These striations run off at angles. These may be dikes of magmas, fractures, or something else. We need to get closer to get a better look."

This section of Spirit’s exploration of Columbia Hills will take around 90 sols, with 60 driving days and perhaps 30 exploration days as the hills get larger in the rover’s panoramic vision.

Related Web Pages

JPL Rovers
Spirit’s Sol images and slideshow
Opportunity image gallery and slideshow
Mars Berries Once Rich in Iron-Water
NASA’s RATs Go Roving on Mars

Water Signs
Microscopic Imager
Gusev Crater
Pancam– Surveying the Martian Scene
Mössbauer spectrometer
Alpha Proton X-ray Spectrometer