Venus's runaway greenhouse effect
Venus's runaway greenhouse effect is a catastrophic climate process where greenhouse gases accumulate in the atmosphere and block thermal radiation from escaping to space, preventing the planet from cooling. On Venus, this likely happened early in its history when water vapor and carbon dioxide trapped heat so effectively that oceans evaporated and liquid water could no longer exist on the surface.
This matters because it shows how planetary climates can become uninhabitable. Venus may have once resembled Earth with habitable conditions before transforming into today's hellish world with surface temperatures of 737 K. Understanding how this happened informs the concept of the habitable zone—the region around a star where planets can sustain liquid water.
Sources
- en.wikipedia.org: “A runaway greenhouse effect occurs when a planet's atmosphere contains greenhouse gas in an amount sufficient to block thermal radiation from leaving the planet, preventing the planet from cooling and from having liquid water on its surface.”
- en.wikipedia.org: “The water vapour reaches the stratosphere and escapes into space via hydrodynamic escape, resulting in a desiccated planet. This likely happened in the early history of Venus.”
- en.wikipedia.org: “Venus may have had liquid surface water early in its history with a habitable environment, before a runaway greenhouse effect evaporated any water and turned Venus into its present state.”