Apparently there's more ice on Mars than we realized. Lots more ice. In fact, Viking 2 came within eight centimetres of uncovering ice on Mars in 1977:
Meteorites that crashed into the Martian surface last year exposed buried ice to the digital eyes of NASA spacecraft. Scientists have used those images to deduce that there is a lot more ice on Mars — and that it's closer to the equator — than previously thought. In fact, subterranean Martian ice should extend all the way down beyond 48 degrees of latitude, according to the model, which was published in Science Thursday. That happens to be where the Viking Lander 2 was in operation from 1976 to 1980. As part of its science program, the Lander dug a trench about 6 inches deep. The new model predicts that if it had gone an extra 3.5 inches — a bit longer than a credit card — it would have hit ice.The only thing I can say is: wow. The whole focus of space exploration during the 1980s and 1990s would have shifted dramatically if the Viking landers had uncovered ice. I don't think we'd have seen an Apollo-style rush to send astronauts there, but there was a hiatus of nearly 20 years after Viking during with the American space science academy mostly ignored Mars, focusing instead on the grand outer planets missions (Galileo and Cassini) and the Hubble space telescope. And the decision to build the international space station in the late 1980s might have gone somewhat differently if there'd been serious competition from a manned Mars mission lobby.