This picture is a thumbnail version of a larger image, video frame, or onboard focus merge product from the Mars Hand Lens Imager (MAHLI) aboard NASA's Mars rover Curiosity. MAHLI is located on the turret at the end of the rover's robotic arm. MAHLI took the larger parent image on February 28, 2018, Sol 1978 of the Mars Science Laboratory Mission, at 15:22:48 UTC.
MAHLI thumbnails are approximately 8 times smaller than the original, parent image. Because the amount of data that Curiosity can send back to Earth each day is limited, small versions of MAHLI's images are sent as soon as possible after a new picture is acquired or produced. The larger image is returned on a prioritized basis, sometimes right away, but often not for several days, weeks, or months. Some images are never returned. Typically, in these cases, an image was acquired to determine autofocus or was intended to be focus-merged onboard the instrument.
When MAHLI obtained the parent picture, the focus motor count position was 13018. This number indicates the internal position of the MAHLI lens at the time the camera acquired the image (or, for focus merge products, it is the position of the first image merged). This count also tells whether the dust cover was open or closed. Values between 0 and 6000 mean the dust cover was closed; values between 12500 and 16000 occur when the cover is open. For close-up images, the motor count can, in some cases, be used to estimate the distance between the MAHLI lens and target. For example, in-focus images obtained with the dust cover open for which the lens was 2.5 cm from the target have a motor count near 15270. If the lens is 5 cm from the target, the motor count is near 14360; if 7 cm, 13980; 10 cm, 13635; 15 cm, 13325; 20 cm, 13155; 25 cm, 13050; 30 cm, 12970.
Image Credit: NASA/JPL-Caltech/MSSS