On October 31, the Mars Curiosity Rover indulged in a tradition honored by party people everywhere: the self-snapped photo, which the rover took in Gale Crater (Mount Sharp, Curiosity's eventual destination, rises in the distance). But this profile-worthy pic isn't a single shot—it's a mosaic of 55 photos taken by the Mars Hand Lens Imager (MAHLI). The camera, according to Bad Astronomy's Phil Plait, is "designed to be able to take close-up shots of nearby rocks and other features, but can also focus all the way out to infinity, allowing it to take pictures of distant geographical features as well."
MAHLI sits at the end of a 6.5 foot articulated arm. To get a picture of the 1-ton rover, the arm moved around and snapped photos at various angles until the whole port side of was captured; the composite was stitched together by mission engineers back on Earth. A large part of the arm doesn't appear in the photo, and there's a good reason for that. "Imagine taking a photo of yourself with your own camera," says Emily Lakdawalla of the Planetary Society. "You can shoot most of your body, and probably your upper arm, but you'd have to be pretty tricky to shoot an image of the forearm of the arm holding the camera. Curiosity's 'wrist' can't bend far enough for it to 'see' its own 'forearm' with the arm-mounted camera." Parts of the rover's upper "arm" can be seen in the picture. (Check out this cool shot showing all of the images used to make the composite.)
This picture is more than just a vanity shot—it will serve as a baseline, helping engineers assess what kind of shape Curiosity is in as it completes its experiments on the Mars surface; they'll look for things like dust accumulation and wheel wear over time.
When it's not taking glamour shots, Curiosity has been hard at work on our red neighbor. Using X-ray diffraction for the first time beyond Earth, the rover found that Mars' soil is similar to basaltic soils in volcanic regions of Hawaii. The rover's largest instrument, Sample Analysis at Mars (SAM), didn't find any methane when it analyzed the atmosphere. But the absence of methane in this test doesn't mean there's no methane. "That could change over time, depending on how methane is produced and how it is destroyed on Mars," says SAM co-investigator Sushil Atreya of the University of Michigan. SAM has also found clues as to why Mars might have lost its atmosphere.