Planet · Terrestrial planet

Mercury

Type: Terrestrial planet
Diameter: 4,879 km
Distance from Sun: 57.9 M km
Surface gravity: 3.7 m/s²
Mean temp.: 167 °C
Moons: 0

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington · NASA media (public domain)

Overview

Scientific overview

Mercury is a terrestrial planet in orbit around The Sun, at a mean distance of 57.9 million km from the Sun.

Physical characteristics

Mass: 0.33 ×10²⁴ kg
Diameter: 4,879 km
Radius: 2,440 km
Density: 5.427 g/cm³
Surface gravity: 3.7 m/s²
Escape velocity: 4.3 km/s
Rotation period: 1,407.6 h
Mean temperature: 167 °C

Scale

Compared to Earth

Earth

Mercury

Mercury is 2.6× smaller than Earth

4,879 km across · Earth is 12,742 km

Orbit

Distance from Sun: 57.9 million km (0.387 AU)
Orbital period: 0.24 years
Perihelion: 46 million km
Aphelion: 69.8 million km
Eccentricity: 0.205
Orbital inclination: 7°
Axial tilt: 0.034°
Orbital velocity: 47.4 km/s

Gallery

Mercury in Bronze
2014
NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington · NASA media (public domain)
Source archive ↗

Observation

How this was captured

Source: NASA
Observation date: 2013-03-29

Exploration

Sources

The primary and reference sources this topic draws on.

NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.
NASA JPLJet Propulsion Laboratory / Solar System Dynamics
Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.

Quick facts

Type: Terrestrial planet
System: The Sun
Moons: 0

Provenance & sources

review 2026.1

Asteria Scientific Review Process · verification: sourced · accurate

High evidenceconfirmed
Mercury is the smallest planet and the closest to the Sun, with only a tenuous exosphere and the largest day-to-night temperature swing of any planet.
Source: NASA (NSSDCA) — NASA Planetary Fact Sheet · Public domain (US Government work)
- NASA Planetary Fact Sheet, Planetary Fact Sheet

Reviewed by the internal Asteria Scientific Review Process — not an external institutional review. See the evidence framework and authority dashboard.

Scientific citations

Real, source-backed references — primary papers first, then datasets and institutional sources. Formatted through the citation engine; nothing is fabricated.

DatasetApproximate Positions of the Planets

NASA Jet Propulsion Laboratory (Caltech)

Cite (APA / BibTeX)

NASA Jet Propulsion Laboratory (Caltech) (n.d.). Approximate Positions of the Planets. NASA Jet Propulsion Laboratory (Caltech). https://ssd.jpl.nasa.gov/planets/approx_pos.html

@misc{cite:jpl-approx-positions,
  title        = {Approximate Positions of the Planets},
  organization = {NASA Jet Propulsion Laboratory (Caltech)},
  year         = {n.d.},
  url          = {https://ssd.jpl.nasa.gov/planets/approx_pos.html},
  note         = {Public-domain Keplerian orbital elements and rates (Standish) — the method behind the computed planet positions, rise/set, and visibility.}
}

DatasetMercury Fact Sheet

NASA Goddard — NSSDCA

Cite (APA / BibTeX)

NASA Goddard — NSSDCA (n.d.). Mercury Fact Sheet. NASA Goddard — NSSDCA. https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html

@misc{cite:factsheet-planet-mercury,
  title        = {Mercury Fact Sheet},
  organization = {NASA Goddard — NSSDCA},
  year         = {n.d.},
  url          = {https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html},
  note         = {Physical and orbital parameters for Mercury.}
}

Institutional pageMercury — NASA Solar System Exploration

NASA

Cite (APA / BibTeX)

NASA (n.d.). Mercury — NASA Solar System Exploration. NASA. https://science.nasa.gov/

@misc{cite:nasa-planet-mercury,
  title        = {Mercury — NASA Solar System Exploration},
  organization = {NASA},
  year         = {n.d.},
  url          = {https://science.nasa.gov/},
  note         = {NASA overview of Mercury.}
}

Institutional pagePlanets — NASA Science

NASA

Cite (APA / BibTeX)

NASA (n.d.). Planets — NASA Science. NASA. https://science.nasa.gov/planets/

@misc{cite:nasa-planets,
  title        = {Planets — NASA Science},
  organization = {NASA},
  year         = {n.d.},
  url          = {https://science.nasa.gov/planets/},
  note         = {NASA overview of the planets: how the naked-eye planets appear and move through the sky.}
}

Quality & authority

Complete

Reviewed

Description: Complete
Source coverage: Complete
Relationship coverage: Complete
Review coverage: Complete
Citation coverage: Complete
Image coverage: Complete

Data from the NASA Planetary Fact Sheet & JPL (public domain). See source quality.

Mercury

Scientific overview

Physical characteristics

Compared to Earth

Orbit

Gallery

How this was captured

Exploration

MESSENGER

Mariner 10

Sources