Significant reductions in electrical-power demand as well as in related mass and physical volume might be achieved if available extraterrestrial solar irradiance could be utilized for plant production in a Bioregenerative Life Support System (BLSS) on Mars. Working estimates of the available photosynthetic photon flux (PPF) at Chryse Planitia (22.3° N, 47.9° W), landing site for the Viking Lander 1 (VL-1) on Mars and geographically near the Mars Pathfinder's landing site, were simulated based on the year-long actual irradiance measurements and downward spectral characteristics made by VL-1 in the 1970's. The results showed that the Wm−2 to µmol m2 s−1 conversion factors for Earth and Mars are essentially equal, being approximately 4.6 µmol m−2 s−1/Wm−2. For half of the total sunshine hours at Chryse Planitia for a whole Martian year, the incident PPF level is at least 400 µmol m−2 s. At approximately 7 % of the sunshine hours in a Martian year, however, the PPF level is zero owing to weather factors. Replacing the Martian solar irradiance as gathered by a Solar Irradiance Collection, Transmission and Distribution System (SICTDS) with 40% efficiency would require either 0.1 kW of HPS lighting or 0.16 kW of CWF lighting supplied continuously for 8,235 hrs, which is equivalent to approximately 11.5 Earth months. A plant lighting regime on Mars consisting of 200 µmol m−2 s−1 of PPF and 16 hours of photoperiod per Martian day could be supplemented with available solar irradiance on Mars by as much as 33% when using an SICTDS with 40% efficiency.