It was unfortunate, but inevitable, that Mariner 10 imaged the same areas of Mercury at each of its three active passes. It therefore covered less than half of the total surface, and there is little hope of adding the rest from ground-based observations, plus the fact that the Hubble Space Telescope cannot be used (Mercury is always too dangerously near the Sun in the sky). It is particularly tantalizing that one of the main features, now called the Caloris Basin, was only half illuminated when Mariner passed over the planet. There is no reason to believe that the uncharted areas are basically different from those which we have seen, but of course we cannot be quite sure.
KeywordsHubble Space Telescope Solar Nebula Active Pass Transverse Fault Small Crater
Unable to display preview. Download preview PDF.