Mercury (planet)

MercuryMercurioplanet MercuryDe GraftMercurianMercury's orbitplanet(Mercury)3:2 spin–orbit resonancea planet
Mercury is the smallest and innermost planet in the Solar System.wikipedia
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Solar System

outer Solar Systeminner Solar Systemouter planets
Mercury is the smallest and innermost planet in the Solar System. Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like Earth.
Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury.

Sun

solarSolThe Sun
Its orbit around the Sun takes only 87.97 days, the shortest of all the planets in the Solar System.
It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, and render Earth uninhabitable – but not for about five billion years.

Venus

Morning Starevening starplanet Venus
Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, and its apparent distance from the Sun as viewed from Earth never exceeds 28°.
Venus is by far the hottest planet in the Solar System, with a mean surface temperature of 735 K, even though Mercury is closer to the Sun.

Planet

planetsFormer classification of planetsplanemo
Mercury is the smallest and innermost planet in the Solar System.
In order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune.

MESSENGER

Mercury MessengerMErcury Surface, Space ENvironment, GEochemistry and RangingMESSENGER Mercury probe
Two spacecraft have visited Mercury: Mariner 10 flew by in 1974 and 1975; and MESSENGER, launched in 2004, orbited Mercury over 4,000 times in four years before exhausting its fuel and crashing into the planet's surface on April 30, 2015.
MESSENGER was a NASA robotic spacecraft that orbited the planet Mercury between 2011 and 2015, studying Mercury's chemical composition, geology, and magnetic field.

BepiColombo

Mercury Magnetospheric OrbiterBepiColumboMercury Planetary Orbiter
The BepiColombo spacecraft is planned to arrive at Mercury in 2025.
BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury.

Ganymede (moon)

GanymedeNicholson RegioAtmosphere of Ganymede
Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan.
It has a diameter of 5,268 km and is 8% larger than the planet Mercury, although only 45% as massive.

List of natural satellites

eighth-largest moonlargestList of moons
Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan.
Mercury, the smallest and innermost planet, has no moons, or at least none that can be detected to a diameter of 1.6 km.

Terrestrial planet

terrestrial planetsrockyrocky planet
Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like Earth.
Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars.

Titan (moon)

TitanSaturn's moon Titanatmosphere
Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan.
It is the second-largest moon in the Solar System after Jupiter's moon Ganymede, and is larger than the planet Mercury, but only 40% as massive.

List of Solar System objects by size

largest25th-largest bodyequatorial radius
Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan.

Planetary core

corecorescenter of the Earth
Although Earth's high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not as compressed.
In the Solar System, core size can range from about 20% (Moon) to 85% of a planet's radius (Mercury).

Geology of Mercury

geologyMercury's geologycrustal modification
Because knowledge of Mercury's geology had been based only on the 1975 Mariner 10 flyby and terrestrial observations, it is the least understood of the terrestrial planets.
This stems largely from Mercury's proximity to the Sun which makes reaching it with spacecraft technically challenging and Earth-based observations difficult.

Inferior and superior planets

superior planetinferior planetinferior planets
Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, and its apparent distance from the Sun as viewed from Earth never exceeds 28°.
In the reference frame of the Earth, in which the terms were originally used, the inferior planets are Mercury and Venus, while the superior planets are Mars, Jupiter, Saturn, Uranus and Neptune.

List of craters on Mercury

crater on MercuryCraters on Mercurycrater in Mercury
Craters on Mercury range in diameter from small bowl-shaped cavities to multi-ringed impact basins hundreds of kilometers across.
This is a list of named craters on Mercury, the innermost planet of the Solar System (for other features, see list of geological features on Mercury).

Mars

MartianCoordinatesplanet Mars
Mercury's surface is more heterogeneous than either Mars's or the Moon's, both of which contain significant stretches of similar geology, such as maria and plateaus.
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.

Orbital resonance

1:1 resonanceresonancemean-motion resonance
It is tidally locked with the Sun in a 3:2 spin-orbit resonance, meaning that relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun.
Numerical simulations have suggested that the eventual formation of a perihelion secular resonance between Mercury and Jupiter (g 1 = g 5 ) has the potential to greatly increase Mercury's eccentricity and possibly destabilize the inner Solar System several billion years from now.

Escarpment

scarpscarpsescarpments
Escarpments or rupēs are named for ships of scientific expeditions.
On other Solar System bodies such as Mercury, Mars, and the Moon, the Latin term rupes is used for an escarpment.

Crust (geology)

crustEarth's crustcrustal
Based on data from the Mariner 10 mission and Earth-based observation, Mercury's crust is estimated to be 35 km thick.
The crusts of Earth, Moon, Mercury, Venus, Mars, Io, and other planetary bodies formed via igneous processes, and were later modified by erosion, impact cratering, volcanism, and sedimentation.

Late Heavy Bombardment

heavy bombardmentintense early bombardmentEarliest evidence for life
Mercury was heavily bombarded by comets and asteroids during and shortly following its formation 4.6 billion years ago, as well as during a possibly separate subsequent episode called the Late Heavy Bombardment that ended 3.8 billion years ago.
During this interval, a disproportionately large number of asteroids are theorized to have collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars.

Planetary phase

phasesphasefull phase
The planet telescopically displays the complete range of phases, similar to Venus and the Moon, as it moves in its inner orbit relative to Earth, which recurs over its synodic period of approximately 116 days.
The two inferior planets, Mercury and Venus, which have orbits that are smaller than the Earth's, exhibit the full range of phases as does the Moon, when seen through a telescope.

Caloris Planitia

Caloris BasinCalorisCaloris impact
During this time Mercury was volcanically active; basins such as the Caloris Basin were filled by magma, producing smooth plains similar to the maria found on the Moon.
Caloris Planitia is a plain within a large impact basin on Mercury, informally named Caloris, about 1,550 km in diameter.

Impact crater

cratercratersimpact basin
The impact that created the Caloris Basin was so powerful that it caused lava eruptions and left a concentric ring over 2 km tall surrounding the impact crater.
Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids.

Moon

lunarthe MoonLuna
Mercury's surface is more heterogeneous than either Mars's or the Moon's, both of which contain significant stretches of similar geology, such as maria and plateaus. Mercury's surface appears heavily cratered and is similar in appearance to the Moon's, indicating that it has been geologically inactive for billions of years. Like the Moon, the surface of Mercury has likely incurred the effects of space weathering processes, including Solar wind and micrometeorite impacts.
Elements that have been detected include sodium and potassium, produced by sputtering (also found in the atmospheres of Mercury and Io); helium-4 and neon from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle.

Space weathering

space-weathereddarkenslighter, disturbed soil
Like the Moon, the surface of Mercury has likely incurred the effects of space weathering processes, including Solar wind and micrometeorite impacts.
The environment at Mercury also differs substantially from the Moon.