By Wanda Starr
Updated Mar 24, 2022
Venus’s dense atmosphere, composed mainly of carbon dioxide with clouds of sulfuric acid, creates a runaway greenhouse effect that traps heat. Surface temperatures regularly reach 864 °F (462 °C), hot enough to melt lead. NASA missions to Venus survive only a few hours on the surface because of this extreme heat.
Mercury, the innermost planet, experiences the largest temperature range in the solar system. Without a substantial atmosphere, its sunlit side can soar to about 800 °F (427 °C), while the night side plunges to as low as -290 °F (-179 °C). These extremes are a result of Mercury’s negligible atmospheric insulation.
Jupiter’s massive hydrogen‑helium envelope keeps its atmospheric temperature at roughly -234 °F (-151 °C). Though far from the Sun, its internal heat source keeps it warmer than the ice giants farther out.
Saturn’s atmosphere, dominated by hydrogen and helium, cools to about -288 °F (-182 °C) at its upper layers. Its iconic rings are composed of ice chunks and rocky material, reflecting the planet’s cold environment.
Neptune, 30 times farther from the Sun than Earth, reaches an average atmospheric temperature of about -214 °F (-137 °C). Its blue hue is largely due to methane in its atmosphere, and scientists suspect additional unknown gases may influence its appearance.
Uranus is the coldest planet in the solar system, with temperatures dropping to around -357 °F (-219 °C). Its methane, hydrogen, and helium atmosphere gives it a greenish tint, while the bulk of its mass consists of water, methane, and ammonia ices.
Earth’s seasonal variations bring some regions as cold as -126 °F (-80 °C), comparable to Mars’s winter lows of -125 °F (-79 °C). Both planets are too hostile for liquid water to persist long on their surfaces, though evidence suggests water once existed on Mars.
