Sol 37 (Sept. 12, 2012) was Curiosity's last day of characterization activities for its robotic arm. The sol's activities included a vibration test for the device on the arm that processes samples of soil, or powdered rock, collected by the scoop or drill. This device, the Collection and Handling for In-situ Martian Rock Analysis, or CHIMRA, has chambers and labyrinths for sorting, sieving and portioning the samples before the arm delivers them to analytical instruments.
The Sol 37 characterization activities also included imaging of the rover's observation tray by the Mars Hand Lens Imager (raw image at http://1.usa.gov/SeDdsY).
In addition, Curiosity's science instruments performed observations and measurements, including Mast Camera observations of the Martian moon Phobos passing in front of the sun.
Curiosity continues to work in good health. Sol 37, in Mars local mean solar time at Gale Crater, ended at 7:54 a.m. Sept. 13, PDT.