After enduring seasonal dust storms much stronger than the rover was designed to survive, Spirit has now been exploring the Red Planet for two Martian years. That is a period of time longer than three years on Earth and more than 10 times the duration of the original 90-day mission. In fact, on Oct. 1, 2007, the rover entered the fifth extension of its original mission!
Spirit has arrived at a field of boulders that the science team is nicknaming after Colorado 14'ers -- Earth peaks taller than 14,000 feet. Atmospheric dust levels continue to wane, and Spirit took advantage of additional sunlight by using solar power to transmit data to Earth at night when the Odyssey orbiter passed overhead. These transmissions will free up more of Spirit's on-board computer memory.
Spirit began studies of a rock known as "Humboldt Peak" at "Site 3a." This particular rock is dark and angular and appears to be similar to "Comanche"-class rocks encountered by the rover earlier in the mission on "Husband Hill." On sol 1339 (Oct. 9, 2007), the rover conducted a communications test with the European Space Agency's Mars Express orbiter. Mars Express will provide backup communications during the entry, descent, and landing of the Phoenix mission, due to arrive near the north pole of Mars on the United States' Memorial Day weekend of 2008.
The relays with Mars Express are a prime example of the value of having multiple spacecraft at Mars -- by using the same UHF radio frequencies as those used by the rovers and Mars Express, Phoenix will benefit from tried-and-true communications links already in place. Another example is Spirit's ability to take thermal measurements looking up into the atmosphere that fill in data that cannot be collected from above by orbiters looking down. The result is a more complete profile of the Martian atmosphere.
In addition to measuring atmospheric dust levels (known as tau measurements) with the panoramic camera and surveying the sky and ground with the miniature thermal emission spectrometer, Spirit completed the following activities:
Sol 1337 (Oct. 7, 2007): Spirit acquired full-color images, using all 13 filters of the panoramic camera, of boulders at Site 3a. The rover approached Humboldt Peak and acquired post-drive images with the hazard avoidance and navigation cameras.
Sol 1338: Spirit completed a survey of rock clasts and acquired thumbnail images of the sky with the panoramic camera. The rover calibrated the miniature thermal emission spectrometer and acquired data from "Mt. Elbert" with the miniature thermal emission spectrometer. The rover transmitted data to Earth overnight via the Odyssey orbiter.
Sol 1339: Spirit calibrated the miniature thermal emission spectrometer and performed late-night tests of communications with the Mars Express orbiter.
Sol 1340: Spirit searched for morning dust devils with the navigation camera and checked for drift (changes with time) in the miniature themal emission spectrometer. Spirit acquired a stereo mosaic of microscopic images of Humboldt Peak and placed the alpha-particle X-ray spectrometer on the target for overnight studies prior to brushing the surface. The rover surveyed a target known as "Crestone Needle" with the miniature thermal emission spectrometer and then conducted an 18-hour, overnight study of Humboldt Peak with the alpha-particle X-ray spectrometer, while also relaying data to Earth via the Odyssey orbiter.
Sol 1341: Spirit took spot images of the sky with the panoramic camera, checked for drift in the miniature thermal emission spectrometer, and brushed the surface of Humboldt Peak with the rock abrasion tool. The rover placed the alpha-particle X-ray spectrometer on the newly brushed surface. Spirit surveyed targets dubbed "Snowmass" and "Castle Peak" with the miniature thermal emission spectrometer. The rover conducted a 19-hour, overnight study of the brushed surface of Humboldt Peak with the alpha-particle X-ray spectrometer.
Sol 1342 (Oct. 12, 2007): Plans called for Spirit to look for morning clouds with the navigation camera and check for drift in the miniature thermal emission spectrometer. The rover was to switch tools to the Moessbauer spectrometer and spend 23 hours collecting data from the brushed surface of Humboldt Peak with the instrument. Spirit was also scheduled to relay data to Earth during the overnight pass of the Odyssey orbiter and acquire data from a target known as "Mt. Evans" using the miniature thermal emission spectrometer. The next morning, the rover was expected to survey the sky with the panoramic camera.
As of sol 1337 (Oct. 7, 2007), Spirit's total odometry was 7,261.29 meters (4.5 miles).