Venus didn't appear to have any visual features except when passing directly between sun and earth (called transit of Venus). In an attempt to study Venus' parallax, an expedition was setup to observe it from many different places on earth. This effort failed because the time when venus entered and left the solar shadow could not be determined accurately. Lomonosov suggested this might be due to fuzziness caused by an atmosphere, and was right!
A visual chronology of Asimov's ~1500 scientific inventions and discoveries.
