Mercury size and scale context

Mercury is the smallest planet in the Solar System and the closest one to the Sun. Because of its unusual spin-orbit rhythm, one Mercury solar day lasts 176 Earth days, which is longer than its 88-day year. Read its scale context, comparisons, and journey links on the canonical object page.

PlutoDwarf planet·2,380 km

MoonRocky moon·3,470 km

MercuryTerrestrial planet·4,879 km

MarsTerrestrial planet·6,779 km

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Between the smallest and the largest, perspective is everything.

About

Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.

Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.

Editorial

Solar System Planets From Electron to Atoms Stars To Scale Birth And Death Of Stars Black Holes To Scale

Views

Planets of the Solar System Stars of the Universe Black holes Subatomic scale

Open Scale of Space Browse all comparisons

Between the smallest and the largest, perspective is everything.

About

Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.

Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.

Editorial

Solar System Planets From Electron to Atoms Stars To Scale Birth And Death Of Stars Black Holes To Scale

Views

Planets of the Solar System Stars of the Universe Black holes Subatomic scale

Open Scale of Space Browse all comparisons

Moons

Moon

The Moon is Earth's natural satellite and our clearest visual anchor on planetary scale. It is still drifting away from Earth by about 3.8 centimeters each year, a slow tidal migration that has been reshaping the Earth-Moon system for billions of years.

Scale fact3,470 kmdiameter

Object class: Rocky moon
Mass: ~0.012 Earth masses
Host: Earth
Estimated age: ~4.5 billion years
Composition: Silicate rock

Planets

Mercury

Scale fact4,879 kmdiameter

Object class: Terrestrial planet
Mass: ~0.055 Earth masses
Host: Sun
Estimated age: ~4.5 billion years
Composition: Metal-rich silicate rock
Temperature: ~440 K mean surface

Planets

Mars

Mars is the fourth planet from the Sun and the Solar System’s best-studied cold desert world. Ancient river valleys, lake beds, and minerals formed in water show that it once had a much wetter surface environment, even though today it is dry, thin-aired, and intensely cold.

Scale fact6,779 kmdiameter

Object class: Terrestrial planet
Mass: ~0.107 Earth masses
Host: Sun
Estimated age: ~4.5 billion years
Composition: Silicate rock, iron-rich minerals, polar ice
Temperature: ~210 K mean surface