Curiosity’s robotic arm is 2.1 m (6.9 ft) long, weighs 30 kg (66 lb) and has a diameter, including mounted tools, of about 60 cm (24 in). The arm helps scientists get up close and personal with Martian rocks and soil.
The arm makes use of three joints, the rover’s shoulder, elbow and wrist, to extend it forward and to stow it while driving. The cross shaped turret or “hand” holds five devices and can spin 350 degrees giving it the ability to work as a human geologist would. Curiosity can take samples and analyze the elemental composition of rocks and soil.
Two of the instruments on the turret are the Alpha Particle X-ray Spectrometer (APXS) and the Mars Hand Lens Imager (MAHLI). APXS measures the elemental composition of samples by irradiating them with alpha particles and mapping the X-rays that are re-emitted. The MAHLI camera, as discussed in our previous article, can acquire microscopic images of rocks and soil and because it is mounted at the end of Curiosity’s arm, it can take panoramic images of the rover to make sure everything is running properly. The remaining three devices are used gather samples and prepare them for analysis. They are a percussion drill, a brush and a mechanism for scooping, sieving and portioning samples of powdered rock and soil. The drill can make a hole with a diameter of 1.6 cm up to 5 cm deep. The arm can also deliver samples to other instruments in the rover.
Next time: Looking at Curiosity’s Wheels and Legs
“Curiosity is the very basis of education and if you tell me that curiosity killed the cat, I say only the cat died nobly.” – Arnold Edinborough