built by the Jet Propulsion Laboratory
The Robotic Arm (RA) is critical to the operations of the Phoenix lander and is designed to dig trenches, scoop up soil and water ice samples, and deliver these samples to the Thermal and Evolved Gas Analyzer and Microscopy, Electrochemistry and Conductivity Analyzer instruments for detailed chemical and geological analysis. Designed similar to a back hoe, the RA can operate with four degrees of freedom: (1) up and down, (2) side to side, (3) back and forth, and (4) rotate around.
Image right: Phoenix robotic arm. Image credit: NASA/JPL/UA/Lockheed Martin + Full caption
The RA will be 2.35 meters (just under 8 feet) long with an elbow joint in the middle, allowing the arm to trench about 0.5 meters (1.6 feet) below the martian surface, deep enough to where scientists believe the water-ice soil interface lies. At the end of the RA is a moveable scoop, which includes ripper tines (sharp prongs) and serrated blades. Once icy soil is encountered, the ripper tines will be used to first tear the exposed materials, followed by applying the serrated blades to scrape the fractured soil. The scoop will then be run through the furrows to capture the fragmented samples, ensuring enough sample mass for scientific study on the lander platform.
A similar RA developed for the Mars Polar Lander was tested at Death Valley in 2000 and successfully dug a 10-inch trench in just under 4 hours. The extremely hard soil conditions at Death Valley are similar to those expected at Phoenix's martian arctic landing site.