Planet Mercury: Its Real Color and More Fun Facts

Planet Mercury is odd in so many ways; it’s hard to find aspects that aren’t strange. What color is Mercury, really? And does it have the hottest surface temperature? Here are 10 fun facts about the smallest planet in our solar system.

Quick Facts About Mercury

Mercury’s rotation period and solar day are different: It turns once on its axis in about 59 Earth days, but its motion around the Sun stretches the interval between sunrises to 176 Earth days.

10 Fun Facts About Planet Mercury

1. Mercury is closest to the Sun—but it isn’t the hottest planet. You’d think it would claim that title. Nope! The “hottest of them all” honor belongs to our neighbor Venus, thanks to its dense, heat-trapping atmosphere. Learn more about Venus, the planet of paradox.
2. Mercury is a planet of extremes. Daytime surface temperatures can reach approximately 800°F (430°C)—hot enough to melt lead! At night, temperatures can fall to about −290°F (−180°C). Mercury has an extremely thin exosphere rather than a substantial atmosphere to retain heat.
3. Its year is short, but its day is very long. Named for the swift Roman messenger god, Mercury takes only 88 Earth days to zip around the Sun. However, it takes about 59 Earth days to rotate once on its axis—and 176 Earth days for the Sun to return to the same place in the sky. Now that’s a very long workday!
4. Mercury has the most out-of-round orbit of the eight planets. And Jupiter, of all unlikely villains, can influence its long-term stability. Computer simulations suggest a small possibility that gravitational interactions could stretch Mercury’s orbit enough for a collision with Venus or the Sun within the next 5 billion years. That’s a possible outcome, not a prediction that disaster is inevitable.
5. Mercury goes through phases. Like the Moon, it can appear crescent-shaped, partly illuminated, or nearly full when viewed through a telescope. How much of its sunlit side faces us helps determine its apparent brightness.
6. Mercury is gray, not red. Its rocky, dusty surface generally looks dark gray to human eyes. The brilliant blue, orange, and yellow shades in some spacecraft images are enhanced colors that help scientists distinguish differences in surface materials. They aren’t the colors you’d see from a spacecraft window.
7. The smallest planet is only a little larger than our Moon. Mercury measures about 3,032 miles (4,880 kilometers) across. It may be small, but it is still one of the solar system’s eight planets.
8. Mercury’s battered surface preserves an ancient history. With no substantial atmosphere, rain, or flowing rivers to wear them away, many impact craters remain visible. But Mercury hasn’t always been quiet: It has ancient volcanic deposits, and small fault scarps suggest that the planet has continued contracting as its interior cools.
9. There’s ice on this scorching world. Mercury has almost no axial tilt. Deep inside some polar craters, the Sun never rises above the crater walls, leaving permanently shadowed places where water ice can survive. A surprising touch of winter on a world badly needing it!
10. Mercury really does have “weird terrain.” I’m not making that up. Scientists informally gave that name to a jumbled landscape on the opposite side of the planet from the enormous Caloris impact basin. One explanation involves impact-generated seismic waves converging there; another proposes that the ground collapsed as volatile materials escaped. Its origins remain a subject of research.

How to Find Mercury in the Night Sky

As Mercury appears so near the Sun in our sky, it’s often difficult to see. Look for it low in the west after sunset during an evening appearance, or low in the east before sunrise during a morning appearance.

The best opportunities often occur near greatest elongation, when Mercury appears farthest from the Sun in the sky. The dates change throughout the year, so there is no single month or fixed interval after sunset that always works.

Consult the Almanac’s Planet Rise and Set Calculator for your location. Choose an unobstructed horizon, and check whether Mercury is making a morning or evening appearance. For evening viewing, wait until the Sun has fully set before searching with binoculars or a telescope.