Facts About Mercury
Published September 16, 2026 · FactsSeeker
The smallest planet has a surprisingly long day and a short year.
Closest does not mean hottest
Mercury orbits nearest the Sun, but Venus has a hotter surface because of its dense atmosphere. [1]
A year lasts eighty-eight Earth days
Mercury completes an orbit quickly. Its orbital period is much shorter than Earth’s. [1]
Rotation and daylight are different
One spin takes about fifty-nine Earth days. A sunrise-to-sunrise solar day takes about one hundred seventy-six Earth days. [1]
There is no thick atmosphere
Mercury has a very thin exosphere. It cannot retain and distribute heat like Earth’s atmosphere. [1]
It has no moons
No natural satellites orbit Mercury, and the planet has no ring system. [1]
Polar craters can preserve ice
Some polar crater floors remain permanently shadowed. Water ice can survive in these cold traps. [1]
It is the smallest planet
Mercury is only a little larger than Earth’s Moon. Its diameter is roughly one-third of Earth’s. [1]
Its orbit is noticeably stretched
Mercury follows an elliptical path. Its distance from the Sun changes substantially during each short year. [1]
An oversized core lies inside
A large metallic core occupies much of Mercury’s interior. The rocky outer shell is comparatively thin. [1]
Impacts cover the landscape
Mercury’s surface records many asteroid and comet strikes. Large basins and countless smaller craters preserve that history. [1]
Its magnetic field is weak
Mercury has a global magnetic field, but it is much weaker than Earth’s. It still interacts with the solar wind. [1]
Its axis is almost upright
Mercury has very little axial tilt. As a result, it does not experience seasons in the same way Earth does. [1]
Sources & further reading
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Sources checked 2026-09-16. Our approach to facts · Suggest a correction