Update on Line-of-Sight Extinction Seen within Gale Crater, Mars

English Abstract:

The line-of-sight optical depth within Gale Crater has been derived using the Navigation Cameras (Navcam) of the Mars Science Laboratory rover, Curiosity. The images used were initially obtained to observe dust devil frequencies within Gale Crater. All images point due north and contain the local ground, the distant crater rim, and the sky above the crater. The imaging parameters for this observation were standardized on sol 100. The line-of-sight optical depth is compared to column optical depth (using Mastcam) for sols 100 – 360 and is discussed by Moores et al. (2014). As we now have data up to sol 844, this observation has covered more than an entire Martian year. Moores et al. (2014) concluded that values for the line-of-sight extinction were less than the extinction seen in the column optical depth measurements made by Mastcam. After continuing observations we can draw similar conclusions. For the majority of the Martian year, we see a line-of-sight extinction that is less than the column extinction, indicating that the air within the crater is less dusty than the air above the crater. There is a period of 50 sols (sols 600-650; Ls ∼ 130°) in the data in which the derived line-of-sight extinction matches the Mastcam column extinction; this suggests a period in which atmospheric mixing between the air inside the crater with the air surrounding the crater may occur.