Which Planet Is the Hottest? The Surprising Answer

Venus is the hottest planet in the solar system, maintaining a surface temperature of about 867 degrees Fahrenheit (464 degrees Celsius), which is hot enough to melt lead, according to planetary data. Despite Mercury sitting closest to the sun at 36 million miles away, Venus—positioned 67 million miles out—reaches higher temperatures due to a thick atmospheric blanket of carbon dioxide that traps heat continuously, day and night.

The Greenhouse Trap and Atmospheric Pressure

Venus is wrapped in an atmosphere made almost entirely of carbon dioxide, creating surface pressure 92 times greater than Earth’s, roughly equivalent to a submarine 3,000 feet underwater. Sunlight enters the atmosphere easily, but the thick greenhouse layer prevents heat from escaping. Furthermore, Venus reflects about 70 percent of the sunlight that reaches it—more than any other planet in the solar system—yet the greenhouse effect overwhelms this high reflectivity by trapping enough of the remaining 30 percent to drive extreme heat.

A Day Longer Than Its Own Year

Venus rotates backward, with a 177-degree tilt that puts it nearly upside down. One full rotation takes 243 Earth days, which is slower than the 225 Earth days it takes the planet to complete one orbit around the sun. Despite this sluggish spin, one sunrise-to-sunrise solar day lasts about 117 Earth days. Scientists studying the backward spin point to a potential massive collision early in the planet’s history that could have flipped its rotation entirely.

Why Mercury Loses Despite Being Closest

Mercury holds only a trace of atmosphere because solar wind stripped most of it away billions of years ago. Exposed rock on Mercury can reach 800 degrees Fahrenheit in direct sunlight, then drop to around -290 degrees after sunset, creating a temperature swing of over 1,000 degrees in a single day. In contrast, Venus maintains a steady, unrelenting warmth around the clock with almost no temperature variation between its equator and poles.

What Extreme Conditions Mean for Spacecraft

Ten Soviet Venera landers reached the surface of Venus between 1961 and 1984, but none survived long against the crushing pressure, extreme heat, and sulfuric acid clouds that corrode metal over time. Venera 13 set a record among them by surviving 127 minutes and transmitting the first color photographs from the surface. NASA’s Magellan spacecraft later radar-mapped 98 percent of the surface from orbit in the early 1990s, providing the best look humanity has gotten at what’s actually down there.

Future Space Missions to Venus

Space agencies are returning to Venus to investigate how a planet similar in size to Earth became so drastically different. NASA has two new missions in development: DAVINCI, which will drop a probe straight through the atmosphere to sample gases during descent, and VERITAS, designed to map the surface in sharper detail than Magellan. Additionally, the European Space Agency is planning its EnVision orbiter for the coming decade.

Frequently Asked Questions

Why is Venus hotter than Mercury?

Venus traps heat using a dense carbon dioxide atmosphere that creates a powerful greenhouse effect, whereas Mercury has virtually no atmosphere to hold onto heat.

How long is a day on Venus?

One full rotation relative to the stars takes 243 Earth days, while a sunrise-to-sunrise solar day lasts about 117 Earth days.

Are there active missions planned for Venus?

Yes, NASA is developing the DAVINCI and VERITAS missions, and the European Space Agency is planning the EnVision orbiter.