NASA's Mars Exploration Rover Opportunity examined a rock called
"Marquette Island" from mid-November 2009 until mid-January
2010. Studies of texture and composition suggest that this rock,
not much bigger than a basketball, originated deep inside the
Martian crust. A crater-digging impact could have excavated the
rock and thrown it a long distance, to where Opportunity found
it along the rover's long trek across the Meridiani plain toward
Endeavour Crater. This approximately true-color view of
Marquette Island comes from combining three exposures that
Opportunity's panoramic camera (Pancam) took through different
filters during the rover's 2,117th Martian day, or sol, on Mars
(Jan. 6, 2010). On the preceding sol, Opportunity's rock
abrasion tool brushed dust out of the circular area where that
tool had ground into the rock on sols 2100 and 2103 (Dec. 20 and
23, 2009). The dark circle left by the rock abrasion tool's work
is approximately 5 centimeters (2 inches) in diameter.