Scooping up a handful of dirt may seem simple, but for a robot operating on another planet, it’s a major operation. NASA’s Curiosity Mars rover is making itself ready to collect its first soil sample at an area called “Rocknest.” The preparations involve testing the nuclear-powered rover’s motorized scoop and cleaning out its Chemistry and Mineralogy (ChemMin) and Sample Analysis at Mars (SAM) laboratories of any terrestrial contaminants before receiving soil samples.
A key part of Curiosity’s soil analysis is the motorized scoop that’s part of the toolkit at the end of the rover’s seven-foot (2.1 m) robotic arm. The scoop, which goes by the formidable name of Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA), can collect samples down to a depth of 1.4 inches (3.5 cm). Inside, it has a vibration system to move the sample through a series of chambers, labyrinths and sieves that it uses for sorting, sizing and dividing the samples collected by the scoop or CHIMRA’s percussive drill before delivering them to the rover’s internal laboratories.
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As a first step in preparing Curiosity for soil analysis, the 4X4-size explorer scuffs the surface of Mars with one of its wheels to expose fresh soil. Once the soil is collected and processed by CHIMRA, it’s delivered by the robotic arm to Curiosity’s internal laboratories. These consist of ChemMin, which analyzes samples using an x-ray diffraction system and SAM, which uses a battery of devices including a quadrupole mass spectrometer, a gas chromatograph and a tunable laser spectrometer.
The first thing that Curiosity will do when it collects its first sample will be to divide it into four parts, one of which will be set aside to be examined by Curiosity’s cameras. "We're going to take a close look at the particle size distribution in the soil here to be sure it's what we want," said Daniel Limonadi, lead systems engineer for Curiosity's surface sampling and science system at the Jet Propulsion Laboratory (JPL) in Pasadena, California. "We are being very careful with this first time using the scoop on Mars."
Two other parts of the sample will be used to clean out the ChemMin and SAM laboratories. This is done by adding soil to the laboratories and shaking it thoroughly inside the chambers before discarding the sample. This is then repeated with the third and fourth parts of the sample.
The purpose of this is to scrub the surfaces and eliminate any contamination brought from Earth by scrubbing the chambers with the same soil that the labs will analyze. "It is standard to run a split of your sample through first and dump it out, to clean out any residue from a previous sample," said Joel Hurowitz, a sampling system scientist on the Curiosity team. "We want to be sure the first sample we analyze is unambiguously Martian, so we take these steps to remove any residual material from Earth that might be on the walls of our sample handling system."
After this clean-out procedure, the labs will be ready to receive samples for analysis. This is done each time Curiosity moves on to a new sample area.
The area where the test will occur is called “Rocknest.” It’s eight feet by 16 feet (2.5 m by 5 m) and, though covered with sand and dust, provides lots of places to scoop soil as well as a wide variety of rocks to study using both the on board laboratory and the instruments in Curiosity’s mast and arm.
After completing its soil sampling, Curiosity will continue its trek toward Glenelg, an area named after a terrestrial geological formation and also so called because it’s a palindrome and Curiosity will visit the area twice. So far, Curiosity has traveled 1,590 feet (484 m) from Bradbury Landing where the rover touched down on August 6. Its next drive will be about 100 yards (100 m) eastward where it will select a rock as the first target for its sample-collecting drill.
Soil sampling is part of Curiosity's two-year mission to explore Mars in search of sites where life might have or still does exist. Since landing, mission control at JPL has put the robot explorer through a rigorous three-week shakedown followed by a series of test drives. During this time, Curiosity fired its rock-vaporizing laser, streamed the first human voice from another planet, wrote messages in the Martian soil, gave itself a thorough self-examination, studied its first rock using its robotic arm, investigated an ancient stream bed and made the first foursquare check-in from another planet.
The video below is a JPL update on Curiosity.