FIG. 8.

VL2 cycle 2 LR responses to first and second injections. After correcting for background, the cumulative radioactivity evolved in the first peak following first nutrient injection was approximately 15% of that evolved during VL2 cycle 1 in the same time period; little else evolved over the subsequent sols. Following second injection, the peaks represent diurnal movement of gas back and forth from the test cell chamber to the detector chamber as determined by turning off the thermal electric coolers for one sol between Sols 10 and 12, which eliminated the fluctuation. [Reprinted from Levin, G.V. and Straat, P.A. (1977a) Recent Results from the Viking Labeled Release Experiment on Mars. J Geophys Res 82(28):4663–4667. ©1977 by the American Geophysical Union; with permission by Wiley.]