Imaging the surface of Mercury using ground-based telescopes

We describe and compare two methods of short-exposure, high-definition grou nd-based imaging of the planet Mercury. Two teams have recorded images of M ercury on different dates, from different locations, and with different obs ervational and data reduction techniques. Both groups have achieved spatial resolutions of <250 km, and the same albedo features and contrast levels a ppear where the two datasets overlap (longitudes 270-360<degrees>). Dark al bedo regions appear as mare and correlate well with smooth terrain radar si gnatures. Bright albedo features agree optically, but less well with radar data. Such confirmations of state-of-the-art optical techniques introduce a new era of ground-based exploration of Mercury's surface and its atmospher e. They offer opportunities for synergistic, cooperative observations befor e and during the upcoming Messenger and BepiColombo missions to Mercury. (C ) 2001 Elsevier Science Ltd. All rights reserved.