Viewed from orbit, the penumbral shadow of Phobos can be seen to move rapidly over the Martian surface. This shadow on the Martian surface has been photographed on many occasions by Mars Global Surveyor. In the 1970s, the "Viking 1" Lander and Orbiter photographed the shadow as well. The Lander detected the penumbral shadow of Phobos passing across it. This was detected only as a slight dimming of the ambient light; the "Viking 1" Lander camera did not image the Sun. The shadow took about 20 seconds to pass over the Lander, moving at about 2 km/s. The shadow was simultaneously imaged from the "Viking 1" Orbiter, which permitted locating the position of the lander in the orbiter pictures. Far more detailed images of the shadow were taken with the arrival in 1997 of the Mars Global Surveyor and its high-resolution Mars Orbital Camera. One such image was taken on 26 August 1999 and shows the shadow at high resolution. This image was featured in a 1 November 1999 NASA press release. By examining maps of Mars we see the shadow is centered at around 10.9°N 49.2°W. We can also look up the original image files at M04-03241 (red) and M04-03242 (blue), part of the gallery of MOC Wide-Angle Images, Region Lunae Palus, Subphase M04. The "image start time" was 03:26:13.01 UTC, the "line integration time" is 80.4800 milliseconds, and the "downtrack summing" factor is 4. Since the shadow is centered at 6400 pixels from the bottom of the original 10800-pixel-high image (Mars Global Surveyor had a south-to-north Sun-synchronous orbit), we add (6400 × 0.08048 × 4) = 2060.3 seconds = 34 minutes 20.3 seconds to get a time of 04:00:33.3 UTC for the center of the shadow. Putting in the longitude/latitude/altitude coordinate values -310.8,10.9,0 into JPL Horizons we see that the predicted time of mid-transit was 04:00:36 UTC, in perfect agreement within the error of determining the exact longitude and latitude of the center of the shadow. This was about 14:41 Martian local solar time, and the Sun's altitude was 46.5° above the horizon.