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Press Release Images: Spirit
This image shows the martian twilight sky at Gusev crater
Twilight at Gusev

Here is the martian twilight sky at Gusev crater, as imaged by the panoramic camera on NASA's Mars Exploration Rover Spirit around 6:20 in the evening of the rover's 464th martian day, or sol (April 23, 2005). Spirit was commanded to stay awake briefly after sending that sol's data to Mars Odyssey at sunset. This small panorama of the western sky was obtained using camera's 750-nanometer, 530-nanometer and 430-nanometer color filters. This filter combination allows false color images to be generated that are similar to what a human would see, but with the colors exaggerated. In this image, the bluish glow in the sky above where the Sun had just set would be visible to us if we were there, but the redness of the sky farther from the sunset is exaggerated compared to the daytime colors of the martian sky.

These kinds of images are beautiful and evocative, but they also have important scientific purposes. Specifically, twilight images are occasionally acquired by the science team to determine how high into the atmosphere the martian dust extends, and to look for dust or ice clouds. Other images have shown that the twilight glow remains visible, but increasingly fainter, for up to two hours before sunrise or after sunset. The long martian twilight compared to Earth's is caused by sunlight scattered around to the night side of the planet by abundant high altitude dust. Similar long twilights or extra-colorful sunrises and sunsets sometimes occur on Earth when tiny dust grains that are erupted from powerful volcanoes scatter light high in the atmosphere. These kinds of twilight images are also more sensitive to faint cloud structures, though none were detected when these images were acquired. Clouds have been rare at Gusev crater during Spirit's 16-month mission so far.

Image credit: NASA/JPL/Texas A&M/Cornell
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This image shows the tracks created by Spirit rover
The Zen-Like Quality of Mars

Like a circular ripple intersecting a flowing stream, the tracks created by NASA's Spirit rover are reminiscent of a Zen rock garden. Highly prized in Japan, such gardens use rocks and raked gravel to suggest entire landscapes of islands, seas, and streams. A centuries-old Buddhist and Taoist tradition, the creation and contemplation of rock gardens serves to reduce the complexity of life and allow the individual to develop inner calm, though whether or not Spirit is developing robotic inner calm may be open to speculation.

Spirit took this mosaic of images with the navigation camera on martian day, or sol, 476 (May 5, 2005), at the end of a drive. Spirit previously had to abandon climbing hills on Sol 455 (April 14, 2005) because of steep slopes. The backtracking was fortuitous, allowing the science team to discover layered outcrops of rock that had been overlooked on the first drive past this area. Since then, Spirit has been examining those "Methuselah" outcrops in the "Columbia Hills" for several weeks. This mosaic looks back at the tracks Spirit left while backtracking and heading to "Methuselah."

Image credit: NASA/JPL
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