The answer first
Venus’s thick carbon-dioxide atmosphere and clouds sit above a surface near 475°C and roughly 92 times Earth’s sea-level pressure. Its greenhouse effect dominates the comparison with Mercury.
Soviet Venera landers measured the surface directly. Radar missions later mapped terrain hidden by clouds.
The idea that changes the view
Distance from the Sun did not decide the hottest planet; atmosphere did.
What most explanations leave out
Sulfuric-acid rain evaporates before reaching the hot surface; ‘rains acid’ needs that qualifier.
Evidence and named signals
- Venera returned surface images and measurements.
- Magellan mapped topography by radar.
- Atmospheric isotope ratios point to major water loss.
What remains uncertain
How long early Venus retained temperate conditions remains model-dependent.
Why it matters—or what you can observe
Venus is a laboratory for planetary climate boundaries—not a one-to-one forecast for Earth.
Related StarPixels video · 5:06
Earth’s Twin Went Wrong—Here’s How
Venus began with Earth-like ingredients and became a world that melts lead.
Open the video companionFurther reading and primary sources
- NASA Venus factsSource checked 2026-07-16
- NASA NSSDC VeneraSource checked 2026-07-16
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