THE radar images of Venus sent by the Magellan spacecraft in the last few weeks are 10 times sharper than any that scientists have seen before. But already ``that factor of 10 has revealed a whole new planet,'' planetologist Ellen Stofan says. Dr. Stofan, who is assistant to the Magellan project scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., notes that ``there's a lot of things we don't really understand.'' The flow of images, she says, ``is overwhelming and terribly exciting.''
Joseph Boyce, Magellan program scientist for the National Aeronautics and Space Administration (NASA), has expressed similar enthusiasm. The razor-sharp images show Venus to be what he calls an ``amazing place,'' with some features not seen before in the solar system.
Linear markings that look like fault lines crosshatch large areas. Craters - both volcanic and meteoritic - pockmark the surface and etch their patterns into long ranges of mountains. Lava flows abound. ``Almost everywhere you look on Venus you see volcanic features,'' Stofan notes. It is, she adds, a geologically active planet.
The image with three volcanic craters (lower photo) illustrates her point. Deposits of material that show up as both light and dark patches stretch out from the craters. These look like the fallout from volcanic explosion plumes seen on Earth, according to JPL, which manages the Magellan mission for NASA.
The image of the roughly oval-shaped crater (upper right) is one of the features that Magellan investigator James Head of Brown University in Providence, R.I., considers unique in the solar system. It lies in the Navka Region at 21.4 south latitude, 334.5 east longitude. Its shape may reflect the thickness of the Venusian atmosphere, with surface pressure 90 times that of sea-level pressure on Earth. Dr. Head has explained that, probably, only the larger meteorites get through that atmosphere. Moreover, some may break up and flatten on their way in. The object that blasted out this crater may have arrived looking more like a pancake than a rotund meteorite.
Another unique - and puzzling - feature is the pattern of intersecting lines (upper left), located at 30 degrees north latitude, 333.3 degrees east longitude. The width of these lines is at the limit of the radar's resolution. It can show details down to about 120 meters (400 feet) across. The thicker lines that intersect the faint lineations at right angles are not regularly spaced and sometimes appear to begin and end at one of the faint lineations.
Asked if this strange pattern might be due to data errors or distortion, Stofan says, ``The pattern is real. It goes on over a vast area. We see nothing like it on Earth.''
One geological factor unique to Venus is the heavy atmosphere and high surface temperature of 730 kelvin (850 degrees F). Under these conditions, the surface is more plastic than Earth's. Stofan explains that ``land features relax away'' in the geologically relatively short period of a few hundred million years. Scientists must learn to take this into account in interpreting what Magellan shows.
The spacecraft began sending data Sept. 15 after JPL engineers overcame communications problems they still don't understand.