Statistical characterization of PIXL trace element detection limits

Trace element detection and mapping are key capabilities of the Planetary Instrument for X-ray Lithochemistry (PIXL) on board the Mars 2020 rover Perseverance. However, poor signal-to-noise ratios due to the short integration times required to make high-spatial-resolution map scans operationally feasible raise the possibility of misidentifying statistical noise as a signal from a trace element, which can cause many false detections of a trace element among the hundreds to thousands of data points in each PIXL scan. Here, we apply a statistical technique to quantify the likelihood of such misidentifications and determine what concentration of a trace element must be present to reach statistical confidence in a detection. This approach is anticipated to be applicable both when analyzing existing PIXL data to ensure that noise is not misinterpreted as signals from trace elements and operationally to inform scan parameters when trace elements of interest are anticipated to be present.