Simply stated, ChemCam is telling us what the rocks that Curiosity has encountered since landing are made of. The primary objectives of ChemCam are to rapidly analyze rocks and soil to determine their compositions and to identify samples that would be of greatest interest to scientists for analysis by other instruments onboard Curiosity.
Rapid Analysis of Rocks and Soil
Determining the composition of rocks on the Martian surface is usually a laborious, time-consuming task, even for advanced spacecraft such as the Mars Exploration Rovers Spirit and Opportunity. Most rocks on the surface of Mars are covered with a layer of dust. Many rocks are also covered with a layer of material that has been altered by wind and possibly water. To determine the true composition of a rock, spacecraft must first clear away the dust and the altered layer of rock. This involves the spacecraft rolling up to the rock and using a tool to clear away the unwanted layers (Figure 1). Dust can be easily removed but altered layers of rock usually need to be removed by grinding away the material. Another obstacle is the rock grinder. They wear down. In fact the rock grinders on the MER rovers wore down long ago. When conducting a Mars mission, this seemingly menial task may require at least one day’s worth of operations, a long time by mission standards. ChemCam, with its unique laser system, is able to perform the same task in a fraction of the time and without having to contact the rock.
Figure 1. Artist conception of the MER rover approaching a Martian rock for analysis. Credit: NASA/JPL
Determining Composition of Rocks and Soils
Why do scientists care what the rocks and soils of Mars are made of? Knowing a rock’s composition gives scientists 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 will also give scientists clues as to 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 (Figure 2). Part of the ChemCam instrument includes the highest-resolution camera ever sent to the surface of Mars. Mission scientists use this camera to look for physical alteration of rocks caused by the presence of water in the past. ChemCam is not only be able to determine if a rock has been altered by water, it is also able to look for the chemical ingredients of life - oxygen, nitrogen, carbon, and/or hydrogen. Curiosity is the first Mars rover capable of detecting these elements. Detecting these elements, coupled with determining if rocks have been altered by water, will aid mission scientists in assessing the landing area’s potential for past or present biology.
Mars is a windy planet. It is easy for dust to be kicked-up and deposited on rocks, spacecraft, and, one day, astronauts! Well, their suits, anyway. If dust will be covering astronauts, mission planners need to know if there are any toxic materials in the soils of Mars that could be potentially harmful. ChemCam is assisting in the preparation of sending astronauts to Mars by checking for potentially toxic and hazardous materials such as lead and arsenic.
Figure 2. MER MI image of “festooning” on a Martian rock. Festooning is a trait of rock altered by water. Credit: NASA/JPL/Cornell/USGS
Identifying Rocks and Soils for Study by Other Instruments on Curiosity
ChemCam has the unique ability to determine the composition of rocks and soils as Curiosity heads towards Mt. Sharp, but it is not designed to do everything. The suite of science instruments onboard Curiosity is capable of performing numerous other investigations ChemCam is not designed to perform. However, ChemCam is working together with the other instruments to support their investigations. ChemCam uses its high-resolution camera and chemical analyses to pick out rocks and areas of soil that may be of interest to scientists operating other instruments.