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Difficulty: MediumThe Solar System and Planets

Although Mercury orbits closest to the Sun, Venus exhibits the highest average surface temperature of any planet in the solar system. What primary factor accounts for this difference?

  1. A
    Venus possesses an interior layer of metallic hydrogen that generates substantial geothermal heat.
  2. Venus has a dense atmosphere rich in carbon dioxide that produces an extreme greenhouse effect.Answer
  3. C
    Venus is a Jovian body whose thick envelope of helium and methane traps solar radiation.
  4. D
    Venus lacks a solid crust, exposing an active molten mantle directly to incoming solar energy.

Answer

Venus has a dense atmosphere rich in carbon dioxide that produces an extreme greenhouse effect.
Venus is enveloped in a massive atmosphere composed of approximately 96.5% carbon dioxide, producing a powerful runaway greenhouse effect. While solar radiation warms the surface, the thick atmospheric blanket prevents thermal infrared radiation from escaping into space, sustaining surface temperatures of approximately 465°C (870°F). Mercury, despite its closer orbital distance to the Sun, lacks a substantial atmosphere to trap heat.

Step-by-Step Solution

1
Compare the atmospheric characteristics and planetary classifications of Mercury and Venus.
Mercury possesses only a tenuous exosphere, whereas Venus possesses a dense atmosphere roughly 90 times more massive than Earth's, dominated by carbon dioxide (CO2CO_2).
Atmospheric density and chemical composition govern how much thermal radiation a terrestrial planet retains.
2
Determine the thermodynamic process causing Venus to maintain higher temperatures than Mercury.
Solar radiation penetrates Venus's cloud deck, warms the rocky surface, and is re-emitted as infrared radiation, which is strongly absorbed and trapped by the thick CO2CO_2 atmosphere (a runaway greenhouse effect).
Because Mercury lacks an insulating atmosphere, heat rapidly radiates away into space, while Venus retains heat continuously day and night.

Key Concept

Atmospheric greenhouse effect and planetary properties of terrestrial vs. Jovian worlds
Estimated Time:1m 0s
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Topics

The Solar System and Planets

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