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How do the atmospheres of Venus, Earth, and Mars differ?
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Atmosphere
The atmospheres of planets in the solar system are composed of various gases, particulates, and liquids. They are also dynamic places that redistribute heat and other forms of energy. On Earth, the atmosphere provides critical ingredients for living things. Here, feathery cirrus clouds drift across the deep blue sky over Pinawa Dam Provincial Park, near Pinawa, Manitoba, Canada.
The atmospheres of Venus, Earth, and Mars differ significantly in composition, density, and their ability to support life, largely due to their evolutionary histories and distances from the Sun.1
Composition and Density
- Venus: Possesses the most massive atmosphere of the terrestrial planets, composed of more than 96 percent carbon dioxide and 3.5 percent nitrogen. Surface pressure is approximately 95,000 millibars—about 95 times that of Earth.21
- Earth: Features a unique atmosphere composed primarily of nitrogen (78 percent) and oxygen (21 percent), with trace amounts of argon, water vapor, and carbon dioxide.3
- Mars: Has a very thin atmosphere, with surface pressure less than 1 percent of Earth’s. It is composed of about 95 percent carbon dioxide, with the remainder being mostly nitrogen and argon.451
Climate and Evolution
The stark differences in these environments are rooted in how each planet evolved. Earth’s atmosphere was shaped by photosynthesis, which built up oxygen, while much of its early carbon dioxide became locked in crustal rocks. In contrast, Venus’s proximity to the Sun led to a runaway greenhouse effect, trapping heat and resulting in extreme surface temperatures. Mars, once having a thicker atmosphere, lost much of its volatile inventory to space or the ground, leaving it cold and dry.1325