Curiosity landed on Mars on 5 August and began a first-use checkout of rover and instrumental systems (called “CAP-1” and “CAP-2”). CheMin’s first activity on Mars was an “aliveness check” on 9 August in which dark frames (CCD images taken without active cooling and without a powered X-ray source) were collected and sent to ground to test the instrument electronics (all downloaded data were nominal). On 15 August a “health check” was performed, confirming that the CCD cryocooler and X-ray power source were operating satisfactorily. The cryocooler performed better than pre-launch thermal predicts, which suggests that we will get better than anticipated sensitivity and resolution from the detector during surface operations. On 17 August, an electrical test was performed that powered all of the cell and funnel piezodrivers, used for moving the powdered sample through the funnel into the instrument and randomizing the powder in the cells during analysis (all nominal).
On 2 September and 8 September, a full-up operation of the instrument was performed in which an empty cell was analyzed. The results of this test are shown below, in a 2-D image of the CCD showing an energy-filtered Co Ka diffraction pattern of the cell.
This is the first X-ray diffraction pattern ever produced on Mars (or any extraterrestrial object for that matter). The bright inner ring is due to diffraction from the Kapton windows of the cell, and the weaker two rings above it are due to aluminum in the light shield of the CCD. A 1-D transformation of the 2-D image is shown below (similar to a diffractogram obtained from a commercial laboratory XRD). This is identical to the pattern obtained prior to launch.
These results plus the X-ray fluorescence pattern below show that the instrument is operating as expected, and is exhibiting nominal behavior. CheMin is ready to analyze its first sample of Mars soil, to be delivered by the Sample Acquisition, Sample Processing and Handling (SA/SPaH) system. This is expected to occur in mid-October.
In the X-ray fluorescence pattern above, cobalt from the X-ray source is seen, as well as titanium from the sample cell and aluminum from the aluminized light shield that protects the excitation source. Silicon arises from self-fluorescence in the CCD detector.
Since the completion of CAP-2 activities, Curiosity has been moving towards a location called Glenelg, which is about 400 meters away. Glenelg is an exposed region of high thermal inertia (TI) material that represents solid rock (and exposed strata), as opposed to the thin soil layer that Curiosity is now transiting. Near Glenelg, the first soil sample will be ingested by the Sample Acquisition, Sample Processing and Handling (SA/SPaH) system and delivered to both CheMin and the SAM organic analysis instrument (This will occur in mid-late October). This will be CheMin’s first analysis of a sample on Mars. After the strata of Glenelg are imaged, a place will be found to drill an outcrop and deliver drilled material to CheMin and SAM.
Depending on what is found at Glenelg, the Curiosity rover will either perform more imaging/analysis, or begin its long drive to the entry point to Mount Sharp, ~10 km away.