MSL Picture of the Day: T-33 Days: instruments: ChemCam

MSL Picture of the Day: T-33 Days: instruments: ChemCam

Roger Wiens is the principal investigator for ChemCam; he is a geochemist at Los Alamos National Laboratory in New Mexico, US Department  of Energy.
The deputy principal investigator is Sylvestre Maurice, a spectroscopy expert with the Institut de Recherche en Astrophysique et Planétologie at the Observatoire Midi-Pyrénées, Toulouse, France.

ChemCam on the Mast of Curiosity is another instrument which will be of great value to identify what Curiosity is encountering around it.
The Chemistry and Camera suite (ChemCam) is the instrument that uses a rock-zapping laser and a telescope mounted atop Curiosity’s mast. And this up to a distance of 9 meters. The camera suite also contains a telescope, with a diameter of 110 millimeters (4.33 inches), which records monochrome images on a 1,024-pixel-by-1,024-pixel detector. The telescopic camera, called the remote micro-imager, will show context of the spots hit with the laser. It can also be used independently of the laser for observations of targets at any distance.

The rock-zapping is ofcourse not just for special effects and so the ChemCam also includes spectrometers and electronics down inside the rover to read what the zapped rocks were made of.
For its rock-zapping the ChemCam uses a technology called laser-induced breakdown spectroscopy, which has been around for at least 35 years. Laser induced breakdown spectroscopy (LIBS) is spectroscopy of the emission (gas) of atoms and ions in their excited states, by interacting a tightly focused laser beam and the material sample, causing the material to transform in plasma.

ChemCam is its first use in interplanetary exploration, although this method of determining the composition of an object has been used in other extreme environments on Earth. An example of extreme environments is the inside of nuclear reactors. Laser-induced breakdown spectroscopy has also been used on the sea floor. As with many of such inventions it has found its use in cancer detection and has had experimental applications in environmental monitoring.

The laser can hit rock or soil targets up to about 7 meters (23 feet) away with enough energy to excite a pinhead-size spot into a glowing, ionized gas, called plasma. The instrument observes that spark with the telescope and analyzes the spectrum of light to identify the chemical elements in the target.
What makes ChemCam very valuable to the scientist on Earth is that it can check rocks and soil that are beyond the reach of Curiosity’s robotic arm.

The spot hit by ChemCam’s infrared laser gets more than a million watts of power focused on it for five one-billionths of a second. Light from the resulting flash comes back to ChemCam through the telescope, then through about 6 meters (20 feet) of optical fiber down the mast to three spectrometers inside the belly of the rover.  A spectrometer “reads” the light and identifies the types of atoms within the target. ChemCam will be able to distinguish different elements because each chemical element has its own unique “fingerprint.” Sparks from different elements and rock types also have their own color. Knowing which atoms are present in the target rock tells ChemCam scientists its composition.

The spectrometers actually consist of three separate units covering different spectral ranges. The three ranges are 240-336 nanometers, 380-470 nanometers, and 470-850 nanometers. Together the spectrometers record intensity at 6,144 different wavelengths of ultraviolet, visible and infrared light (wavelengths from 240 to 850 nanometers). Different chemical elements in the target, in their ionized state, emit light at different wavelengths.

Dozens of laser pulses on the same spot will be used to achieve the desired accuracy in identifying elements. Among the many elements that the instrument can identify in rocks and soils are sodium, magnesium, aluminum, silicon, calcium, potassium, titanium, manganese, iron, hydrogen, oxygen, beryllium, lithium, strontium, sulfur, nitrogen and phosphorus.

Information from ChemCam will help researchers survey the rover’s surroundings and choose which targets to approach for study with the tools on the arm and the analytical laboratory instruments. This helps with the research as ChemCam can analyze many more targets than those instruments can. It can be used on multiple targets the same day, while the analytical laboratory investigations — SAM and CheMin — take multiple days per target.

Instead of brushing a rock with the Rock Abrassion Tool (RAT) that Spirit and Opportunity used to brush coating of dusts of a rock, ChemCam can hit that rock with hundreds of repeated pulses from the laser to remove the dust. ChemCam’s reading of the rock’s interior composition compared to the composition of the dust that has been ‘vaporised’ gives us inside between the difference between interior of the rock and its coating. ChemCam’s capabitlities are dust removal over a ~1-cm region and depth profiling within a ~1-mm spot.

Researchers also plan to use ChemCam to study the soil at each place Curiosity stops.
ChemCam can also provide certainty in the identification of water if any is on the surface in the area Curiosity explores as ChemCam can identify hydrogen and oxygen quickly. This water can either be bound into mineral composition or as frost. Knowing a rock’s composition gives us clues as to the environment in which the rock formed. These clues help scientists characterize the geology of the rock’s location. The compositions of rocks that have been in contact with water differ from rocks that have not. Finding rocks that have been altered by water gives us insight into whether or not the rock’s surroundings were once a habitable place. The appearance of a rock also gives clues relating to a rock’s exposure to water

All these observations will document local and regional variations in the soil’s composition and in the size distribution of soil particles.

ChemCam was developed, built and tested by a partnership of Los Alamos and researchers in France funded by the French national space agency, Centre National d’Études Spatiales (CNES).

France provided ChemCam’s laser and telescope. The laser was built by Thales, Paris, France. Los Alamos National Laboratory supplied the spectrometers and data processors. The optical design for the spectrometers came from Ocean Optics, Dunedin, Florida.

The ChemCam team includes experts in mineralogy, geology, astrobiology and other fields, with some members also on other Curiosity instrument teams.

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