Forty years ago, NASA's Viking mission made history when it became the first to successfully land a fully operational spacecraft on Mars. As engineers and scientists planned for later missions to Mars, the rolls of microfilm containing the Viking data were stored away for safekeeping and potential later use. It would be another 20 years before someone looked at some of these data again - in a digitised format. "At one time, microfilm was the archive thing of the future. But people quickly turned to digitising data when the web came to be. Now, we are going through the microfilm and scanning every frame into our computer database so that anyone can access it online," said David Williams, planetary curation scientist at Goddard Space Flight Center in Greenbelt, Maryland. The spacecraft, dubbed Viking 1, touched down on the Martian surface on July 20, 1976. Its counterpart, Viking 2, followed suit and landed on September 3 in the same year. The mission objectives were to obtain high-resolution images of the Martian surface, characterise the composition of the Martian surface and its atmosphere and search for life. After years of imaging, measuring and experimenting, the Viking spacecraft ended communication with the team on Earth, leaving behind a multitude of data that scientists would study for the next several years. The archive today houses much of NASA's planetary and lunar spacecraft data stored on microfilm and computer tapes, including the Viking data. Williams works to digitise all of the data so that it can be easily accessed from the web. He received a call from Joseph Miller, associate professor of cell and neurobiology at the University of Southern California, Los Angeles, requesting data from the Viking biology experiments. But all that was left of the data was stored on microfilm.