In the paper ‘Mars: Water Vapor Observations From the Viking Orbiters’ by C. B. Farmer et al. (Journal of Geophysical Research 82(28), 4225–42481, 1977), the color key for Plate 1 is light yellow,0–2 pr μm (precipitable micrometers); dark yellow, 2–4 pr μm; yellow orange, 4–6 pr μm; orange, 6–8 pr μm; red, 8–10 pr μm; green, 10– 15 pr μm; light blue, 15–20 pr μm; dark blue, 20–30 pr μm; blue purple 30–40 pr μm; purple 40–60 pr μm; and black, >60 pr μm. The color key for Plates 2a–2c is purple, 0–10 pr μm; black, 10–15 pr μm; brown, 15–20 pr μm; brownish yellow, 20–25 pr μm; pink, 25–30 pr μm; red, 30–35 pr μm; yellow, 35–40 pr μm; and green, 40–50 pr μm. The color key for Plate 2d is red, <15%; dark blue, 15–20%; light blue, 20–25%; green, 25–30%; orange, 30–35%; yellow, >35%. The key to Figure 9 is missing.