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发帖数: 298 | 1 March 15, 2002 | During the mid-1970s, fortuitous geometry allowed Mariner 10
to zip by Mercury three times in a 12-month period. But that same geometry
precluded the spacecraft from seeing almost half of the innermost planet's
surface — a "terra incognita" that remains virtually unknown nearly three
decades later.
However, as radar facilities on Earth continue to probe the unseen territory
with ever-improving resolution, Mercury is slowly giving up its secrets.
Several days of observations made |
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