Venus is the hottest planet in the Solar System, even though Mercury is closer to the Sun. Its average surface temperature is about 465 °C, hot enough to melt lead. The reason is a runaway greenhouse effect caused by an extremely thick carbon dioxide atmosphere.
Studying Venus helps scientists understand how atmospheres control planetary temperature and climate.
Key Facts
- Average surface temperature of Venus is about 465 °C or 735 K.
- Venus has an atmospheric pressure about 92 times Earth's surface pressure.
- Venus's atmosphere is about 96.5% carbon dioxide, CO2.
- Greenhouse effect: sunlight enters, the surface warms, and infrared radiation is absorbed and re-emitted by greenhouse gases.
- Venus reflects much sunlight because of bright clouds, with an albedo of about 0.75.
- Temperature conversion: K = °C + 273.15.
Vocabulary
- Runaway greenhouse effect
- A process in which trapped heat increases surface temperature enough to strengthen further heat trapping, creating extreme warming.
- Greenhouse gas
- A gas such as carbon dioxide or water vapor that absorbs and re-emits infrared radiation from a planet's surface.
- Albedo
- The fraction of incoming sunlight that a surface or planet reflects back into space.
- Atmospheric pressure
- The force per unit area caused by the weight of gases above a planet's surface.
- Sulfuric acid clouds
- Clouds made of tiny droplets of sulfuric acid that cover Venus and strongly reflect sunlight.
Common Mistakes to Avoid
- Saying Mercury is hottest because it is closest to the Sun is wrong because Venus has a much stronger greenhouse effect and a much thicker atmosphere.
- Ignoring atmospheric pressure is wrong because Venus's 92 Earth atmospheres of pressure help make its atmosphere dense and efficient at trapping heat.
- Thinking bright clouds make Venus cold is wrong because the clouds reflect sunlight, but the carbon dioxide atmosphere still traps infrared heat extremely well.
- Confusing weather temperature with greenhouse warming is wrong because Venus's high temperature is a global atmospheric energy balance effect, not a short-term weather event.
Practice Questions
- 1 Venus has an average surface temperature of 465 °C. Convert this temperature to kelvin using K = °C + 273.15.
- 2 Venus's surface pressure is about 92 times Earth's surface pressure. If Earth's pressure is about 101 kPa, what is Venus's surface pressure in kPa?
- 3 Explain why Venus is hotter than Mercury even though Mercury is closer to the Sun. Include the role of carbon dioxide and infrared radiation.