Venus suffered a massive runaway greenhouse effect, filling its atmosphere with heat-trapping carbon dioxide, resulting in 90 times the surface pressure of Earth and temperatures above 460 degrees Celsius.
In the vacuum of space, the amount of debris-spent rocket stages, splintered satellites, micrometeoroids- numbers in the millions, all zooming about, often at 17,000 mph speeds. They're also constantly hitting each other in a tsuris of exponential littering. Most of these pieces are tiny, and many are not anywhere near the altitude of the ISS. But the area isn't completely clean.