This week, NASA's Mars Exploration Rover Spirit arrived at "Home Plate," a feature that, when seen from orbit, looks like the home plate of a baseball diamond. Home Plate is a roughly circular feature about 80 meters (260 feet) in diameter that might be an old impact crater or volcanic feature. The Spirit team has been eager to get to Home Plate and has been enjoying distant views of the feature and a curious "bathtub ring" of light-colored materials along its edges. The team has pushed the rover hard to get here before the deep Martian winter sets in.
After scientists had identified Home Plate from orbit, they had many theories about what it could be and what they might see. But when Spirit's panoramic camera (Pancam) took this and other images, the science team was stunned. This Pancam image is of an outcrop nicknamed "Barnhill" and surrounding rocks on the north side of Home Plate, showing the most spectacular layering that Spirit has seen.
Pancam and microscopic imager views of the layers in the rocks reveal a range of grain sizes and textures that change from the lower to the upper part of the outcrop. This may help scientists figure out how the material was emplaced. Spirit is also conducting work with its arm instruments to figure out the chemistry and mineralogy of the rocks. Scientists have several hypotheses about what Home Plate could be, including features made by volcanoes and impact craters, and ways that water could have played a role. They are busy trying to figure out what the data from Spirit is really telling us.
As Spirit works at Home Plate during February, the science team is choosing informal names for rocks from the great players and managers of the Negro Leagues of baseball. This outcrop, "Barnhill," is informally named for David Barnhill, the ace of the New York Cubans' pitching staff during the early 1940s. He compiled an 18-3 record in 1941 and defeated Satchel Paige in the 1942 East-West all-star game. Other rocks in the area are informally named for Josh Gibson, "Bullet Joe" Rogan, and Cumberland Posey. Stay tuned this month, as the Baseball Hall of Fame elects more players from the Negro Leagues and Spirit continues to examine these spectacular rocks.
Spirit took this mosaic of images using the panoramic camera on the rover's 746th day, or sol (Feb. 7, 2006), of exploring Mars. Scientists are acquiring and processing image data for more views of the same terrain in approximate true color.