What Is the Hottest Planet in Our Solar System?
You might think Mercury is the hottest planet because it's closest to the Sun — but you'd be wrong.
Quick Answer
Venus is the hottest planet in our solar system, with an average surface temperature of about 465°C (869°F). Despite being nearly twice as far from the Sun as Mercury, Venus's thick atmosphere creates an extreme greenhouse effect that traps heat.
Venus's extreme temperature is caused by a runaway greenhouse effect. The planet's atmosphere is about 96.5% carbon dioxide, and its thick cloud layers of sulfuric acid trap solar energy with devastating efficiency. While Mercury (the closest planet to the Sun) has almost no atmosphere and temperatures that swing wildly between -180°C at night and 430°C during the day, Venus maintains a consistently scorching 465°C across its entire surface — day and night, poles and equator.
The atmospheric pressure on Venus is equally extreme — about 92 times Earth's atmospheric pressure at sea level. Standing on Venus's surface would feel like being 900 meters underwater on Earth. This crushing pressure, combined with the extreme heat, makes Venus the most hostile planetary surface in our solar system. No spacecraft has survived more than about 2 hours on Venus's surface.
Venus is often called Earth's 'evil twin' because the two planets are remarkably similar in size, mass, and composition. Venus is only about 5% smaller than Earth and has 82% of Earth's mass. Scientists believe Venus may have once had liquid water oceans and a more Earth-like climate, but a runaway greenhouse effect billions of years ago boiled away all surface water and transformed it into the hellish world we see today.
The study of Venus is directly relevant to understanding climate change on Earth. Venus serves as a cautionary example of what happens when greenhouse gases spiral out of control. NASA and ESA have announced multiple new Venus missions (VERITAS, DAVINCI+, and EnVision) scheduled for the late 2020s and 2030s, aimed at understanding how a planet so similar to Earth became so radically different.
Key Fact
Venus is the hottest planet in our solar system at 465°C (869°F) — hot enough to melt lead — despite being nearly twice as far from the Sun as Mercury.
Why It Matters
Venus is a natural laboratory for understanding the greenhouse effect — the same process that is driving climate change on Earth, just taken to its extreme conclusion. By studying how Venus's atmosphere trapped heat so effectively, scientists can build better models for predicting Earth's climate future. Venus also challenges our assumptions about habitability: if Venus once had oceans, understanding what went wrong could help us identify which exoplanets might be habitable and which are 'Venus traps.' This makes Venus research directly relevant to the search for life beyond Earth.
Did You Know?
- •A day on Venus (one full rotation) takes 243 Earth days — longer than a Venusian year (225 Earth days). This means a day on Venus is longer than its year.
- •Venus rotates backwards compared to most planets. If you could see through its clouds, the Sun would appear to rise in the west and set in the east.
- •The Soviet Union's Venera program successfully landed multiple probes on Venus between 1970 and 1982 — the only spacecraft to ever land on Venus and transmit data back.
- •Venus is the brightest natural object in Earth's night sky after the Moon. Ancient civilizations called it the 'morning star' and 'evening star,' not realizing it was the same object.
- •In 2020, scientists controversially reported detecting phosphine gas in Venus's clouds — a potential biosignature that could indicate microbial life in the upper atmosphere.
How to Understand Why Venus Is the Hottest Planet
A step-by-step explanation of the runaway greenhouse effect on Venus.
- 1
Start with the atmosphere
Venus has an atmosphere 96.5% carbon dioxide — the most potent greenhouse gas — creating an extreme insulating layer.
- 2
Understand the greenhouse effect
Solar radiation enters but cannot escape, trapped by the thick CO₂ atmosphere, continuously heating the surface.
- 3
Compare with Mercury
Despite being closer to the sun, Mercury has no atmosphere to trap heat, so Venus at 462°C is far hotter than Mercury's 167°C average.
Key Dates
1610
Galileo makes the first telescopic observations of Venus.
1761
Mikhail Lomonosov discovers Venus has an atmosphere during a solar transit.
1970
Soviet Venera 7 becomes the first spacecraft to land on Venus.
1990
NASA's Magellan orbiter maps 98% of Venus's surface using radar.
2031+
NASA's VERITAS and DAVINCI+ missions planned to study Venus.
Related Facts
Frequently Asked Questions
Explore More
Explore more fascinating facts about planets, space, and the cosmos.
Explore SnapFacts