Mars, as photographed by black-and-white television cameras with slow-scan vidicon tubes (very low definition by today's standards), looked bland and uninspiring – until JPL’s Image Processing Lab had its way with the data.

Mariner 9 raw image of martian surface with no processing (small dots are reseau marks). Click to see the same image with enhanced contrast. Click again to go back.

Early techniques used room-sized computers to assist in clarifying and enhancing the images of Mars and Venus as recorded and transmitted by the Mariner space probes – but only within severely restrictive parameters designed to maintain the integrity of what the onboard cameras had recorded.

“The process cannot add features not originally photographed and recorded, but it clarifies details to an impressive degree,” an October 1966 NASA/JPL press release explains.

Late-sixties state-of-the-art tools used in the Image Processing Lab at JPL included hand-held slide rules and the massive IBM mainframe computer. A specialized component, the video film converter (right) exposed the digital information generated by the computer onto 75mm filmstock, which was then developed and printed as 8x10 photos for in-house analysis and public dissemination.

Among the permissible adjustments were the removal of static and other transmission noise and the stretching of contrast to emphasize depth or detail. A grid pattern of dots called reseau marks, engraved on the camera lens, made geometric corrections possible.

The process was tedious – computer scientists used slide rules to write algorithms, fed them into the computer and waited – sometimes for hours – for the computer to process the information and for the monitor to display the results.