# Mercury (planet) <!-- SOLSIM:BEGIN g31 — Solar System explorer state (hand-built on wt-core, specs/solar/); do not hand-edit inside --> **Microsim — three.js (Wikitube framework):** *Mercury in the Solar System explorer* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/solar/Solar_System.html?obj=Mercury&embed=1" data-title="Mercury in the Solar System explorer"></div> *The Solar System explorer locked on this article's state (`?obj=Mercury`); every object and population of the [[PORTAL_Solar_System|Solar System portal]] has its own state in the same scene.* <!-- SOLSIM:END --> *Try: set the speed to 1 month/s and watch Mercury finish a lap in about three seconds, visibly quickening as it swings through the near side of its orbit; switch the scale to true and compare how far its oval path sits off-centre from the Sun with the nearly round orbits of Venus and Earth; press o to hide the orbits and follow the planet alone against the Sun.* **Mercury** is the innermost and smallest of the eight planets, a dense, airless, heavily cratered [[Terrestrial_planet|rocky world]] with a mean radius of 2,439.7 km that circles the [[Sun]] once every 87.969 days.[^nasa-fs] Its metallic core reaches about 83% of the way from the centre to the surface (derived), and three competing hypotheses try to explain how the planet came to be so rich in metal.[^hauck2013][^benz1988] The planet turns on its axis three times for every two trips around the Sun, a resonance discovered by radar in 1965, so that its day from sunrise to sunrise lasts about 176 Earth days.[^pettengill1965][^colombo1965][^nasa-fs] It has no moons, only a vanishingly thin exosphere, and a weak global magnetic field; its surface swings between roughly 100 K and 700 K, yet permanently shadowed craters at its poles hold water ice.[^prockter2005][^chang2012] Because its orbit lies well inside [[Earth]]'s, Mercury never strays far from the Sun in the sky and is seen only low in twilight. It has been followed since Babylonian times, was first shown to orbit the Sun by the phases it displays in a telescope, and has been visited by three spacecraft: Mariner 10, MESSENGER and BepiColombo.[^strom2003][^jpl2008] The body of this article covers the planet's name, its interior, surface, exosphere and magnetic field, the geometry of its orbit and spin including the relativistic advance of its perihelion, its observation from Earth, and the history of its study. The explorer at the top of this page is locked on Mercury: it traces the most eccentric planetary [[Orbit|orbit]] in the [[PORTAL_Solar_System|Solar System]], which carries the planet between 46.0 and 69.8 million km from the Sun, with positions computed from JPL orbital elements.[^jpl-t1][^nasa-fs] ## Nomenclature Mercury appears alternately in the evening sky after sunset and in the morning sky before sunrise, and early observers treated the two appearances as separate objects. Greek astronomers had recognised by about 350 BC that the morning and evening "stars" were one body.[^dunne1978] The Romans gave the planet the name of Mercury, their fleet-footed messenger of the gods, whom they identified with the Greek Hermes; the choice suits a planet that moves against the background stars faster than any other.[^dunne1978][^antoniadi1974] Greek writers also called it Stilbon, "the glittering one",[^cicero] and Hermes, the name modern Greek still uses.[^greeknames] Not every ancient writer followed the Hermes association: Pliny the Elder records that some linked the planet with Apollo.[^smith-planetae] The astronomical symbol ☿ is drawn from the caduceus, the herald's staff of Hermes, with a cross added at its foot in the 16th century.[^duncan1946][^jones1999] Other cultures chose names that describe the same behaviour of a fast, shy planet that never leaves the Sun's neighbourhood; they are covered under [Ancient astronomers](#ancient-astronomers) below. ## Physical characteristics Mercury is one of the four [[Terrestrial_planet|terrestrial planets]], built of rock and metal like [[Earth]], [[Venus]] and [[Mars]]. It is the smallest planet: its volumetric mean radius is 2,439.7 km and its mass 3.301 × 10²³ kg, 5.5% of Earth's.[^nasa-fs] Its surface gravity is 3.70 m/s², a little over a third of Earth's, and its escape velocity is 4.3 km/s.[^nasa-fs] By mass the planet is roughly 70% metal and 30% silicate.[^strom2003] ### Internal structure Mercury's mean [[Density|density]] is 5,429 kg/m³, only about 1.5% below Earth's 5,513 kg/m³ (derived from the fact-sheet values).[^nasa-fs] The comparison understates how metal-rich it is. Earth's interior is squeezed by its own weight, whereas the much smaller Mercury is hardly compressed at all; with that effect removed, the uncompressed density is estimated at 5.3 g/cm³ for Mercury against 4.4 g/cm³ for Earth.[^usgs2003] A high density without compression can only come from a large core of [[Iron|iron]].[^lyttleton1969] Radio tracking of MESSENGER and Earth-based radar measurements of the planet's spin fix its moment of inertia factor at 0.346, which models turn into a core radius of about 2,020 km.[^margot2012][^hauck2013] With a planetary radius of 2,440 km, that core fills about 57% of Mercury's volume (derived); Earth's core fills about 17%. Above the core lies a silicate mantle and [[Crust_(geology)|crust]] about 420 km thick in total.[^hauck2013] Estimates of the crust alone depend on method: gravity-to-topography ratios suggest about 35 km, while an isostatic model gives a thinner crust of about 26 km.[^padovan2015][^sori2018] The core itself is layered. Radar observations of small oscillations in the planet's spin showed in 2007 that at least part of it is molten, and later analyses of MESSENGER data point to a solid inner core beneath the liquid layer.[^nrao2007][^agu2023] The core probably contains [[Nickel|nickel]], silicon and perhaps [[Sulfur|sulfur]] and carbon alongside iron.[^nittler2018] Why the core is so large is still debated. In the giant-impact hypothesis, a proto-Mercury about 2.25 times its present mass, with an ordinary chondritic mix of metal and rock, was struck by a body about a sixth of its mass that blasted away most of the mantle.[^benz1988] In a second scenario, the young Sun heated the inner nebula to perhaps 2,500–3,500 K, hot enough to vaporise surface rock that the solar wind then swept away.[^cameron1985] A third proposes that gas drag in the nebula sorted grains by density before they were accreted, so that the planet collected metal preferentially.[^weidenschilling1978] MESSENGER found more potassium and sulfur at the surface than the first two models allow, since those volatile elements would have been driven off by extreme heating; the result is taken to favour the third hypothesis, pending further analysis and the BepiColombo measurements.[^sappenfield2011][^cartwright2011] ### Surface geology At first sight Mercury resembles the [[Moon]]: heavily cratered terrain, broad smooth plains and bright ray systems, a pattern that indicates large-scale geological activity ended billions of years ago.[^morris2008] Its crust is low in iron but rich in sulfur, the product of more strongly reducing conditions during formation than on the other terrestrial planets. Iron-poor pyroxene and olivine, sodium-rich plagioclase and sulfide minerals dominate the surface, and the darkest regions contain carbon, probably as graphite.[^nittler2019] The features carry names under the IAU system: craters honour deceased artists, musicians and writers, escarpments are named after ships of scientific expeditions, and valleys after abandoned ancient settlements.[^usgs-categories] The largest impact structure, Caloris Planitia, is about 1,550 km across, roughly a third of the planet's diameter (derived).[^shiga2008] It is ringed by mountains about 2 km high and floored by plains broken by ridges and fractures; opposite it, on the far side of the planet, lies hilly, jumbled ground that may have been shattered by seismic waves from the impact converging at the antipode.[^spudis2001][^schultz1975] In all, 46 impact basins have been identified.[^fassett2012] Mercurian craters throw their ejecta over a smaller area than lunar craters of the same size, a consequence of Mercury's stronger surface gravity.[^spudis2001] Two plains units are recognised: gently rolling intercrater plains, the oldest visible surfaces, and younger smooth plains that fill depressions and are thought, from their shapes and settings, to be volcanic floods.[^spudis2001][^wagner2001] The planet has also shrunk. As the interior cooled, the crust was pushed together into lobate scarps, thrust-fault cliffs that cut across craters and plains. The largest are about 1,000 km long and up to 3 km high.[^choi2016] Mapping these features suggests that Mercury's radius has decreased by about 1–7 km, and most motion on the major thrust systems ended about 3.6–3.7 billion years ago.[^watters2016][^giacomini2020] Very small scarps, tens of metres high and apparently younger than 50 million years, indicate that contraction continues.[^watters2016] Volcanism left its own record: 51 pyroclastic deposits from explosive eruptions have been catalogued, 90% of them inside impact craters, and a compound volcano of at least nine overlapping vents lies within the Caloris rim.[^goudge2014][^rothery2014] ### Surface conditions and exosphere With no atmosphere to spread heat, surface temperatures range from about 100 K to 700 K.[^prockter2005] The subsolar point reaches about 700 K when Mercury is at perihelion and only about 550 K at aphelion, and the nightside averages about 110 K.[^lewis2004][^vasavada1999] Sunlight at the surface ranges from 4.59 to 10.61 times the solar constant, a factor of 2.3 that follows directly from the ratio of the squares of the aphelion and perihelion distances (derived).[^lewis2004][^nasa-fs] The poles never exceed about 180 K, and the floors of deep polar craters, never touched by direct sunlight, stay below about 102 K.[^vasavada1999][^ingersoll1992] Those cold traps hold ice. Radar mapping with Goldstone and the Very Large Array in the early 1990s found highly reflective patches at the poles, and MESSENGER imaging later confirmed water ice in north polar craters.[^slade1992][^chang2012] The deposits are estimated at 10¹⁴–10¹⁵ kg and may be delivered by comets or outgassed from the interior.[^rawlins1995] What passes for an atmosphere is a surface-bounded exosphere with a pressure below about 0.005 picobar (5 × 10⁻¹⁵ bar).[^nasa-fs] Its atoms, including [[Hydrogen|hydrogen]], [[Helium|helium]], [[Oxygen|oxygen]], [[Sodium|sodium]], [[Potassium|potassium]], [[Calcium|calcium]] and [[Magnesium|magnesium]], are continually lost and resupplied: from the [[Solar_wind|solar wind]], from [[Radioactive_decay|radioactive decay]] in the crust, and from rock vaporised by micrometeorite impacts.[^milillo2005][^killen2007] MESSENGER detected magnesium in 2008, and water-group ions in the planet's space environment.[^mcclintock2009][^zurbuchen2008] NASA regards the surface as unsuitable for Earth-like life.[^nasa-indepth] ### Magnetic field and magnetosphere Mariner 10 found in 1974 that Mercury has a global, dipolar magnetic field, about 1.1% as strong as Earth's, a surprise for a small planet that rotates once every 59 days.[^ness1978][^seeds2004] The dipole is closely aligned with the spin axis, and the field's strength and shape have been stable between Mariner 10 and MESSENGER.[^messenger2008] The likeliest source is a dynamo in the liquid outer core, kept partly molten by tidal heating in the eccentric orbit.[^christensen2006][^spohn2001] The field is strong enough to hold off the [[Solar_wind|solar wind]] and form a small magnetosphere, small enough that it would fit inside Earth, which traps solar-wind plasma and contributes to space weathering of the surface.[^beatty1999][^messenger2008] During its second flyby, on 6 October 2008, MESSENGER crossed twisted bundles of magnetic flux up to 800 km wide that connect the planet's field to interplanetary space. Through these flux transfer events the solar wind reaches the surface, and magnetic reconnection runs about ten times faster than at Earth.[^steigerwald2009] ## Orbit, rotation, and longitude Mercury's orbit has an eccentricity of 0.2056, the largest of any planet: its distance from the Sun ranges from 46.0 million km at perihelion to 69.8 million km at aphelion, around a semi-major axis of 57.9 million km (0.387 [[Astronomical_unit|AU]]).[^nasa-fs] By [[Kepler's_laws_of_planetary_motion|Kepler's second law]] its speed changes accordingly, from 58.97 km/s at perihelion to 38.86 km/s at aphelion.[^nasa-fs] The orbit is also inclined by 7.0° to the [[Ecliptic|ecliptic]], the most of any planet, so a transit across the Sun's disc happens only when Mercury passes between Earth and the Sun near a crossing of the ecliptic, in May or November, on average about once every seven years.[^nasa-fs][^espenak2005] The Sun raises a tidal bulge on Mercury about 17 times stronger than the Moon raises on Earth.[^vanhoolst2003] The axis is almost perpendicular to the orbit, tilted by only about 0.03°, which is why the floors of polar craters can stay dark permanently.[^margot2007][^nasa-fs] Averaged over time, Mercury is the planet closest to Earth, and to each of the other planets, because it never moves far from the Sun.[^stockman2019] The explorer draws the orbit from JPL elements, so its off-centre shape and the planet's changing speed around it are real.[^jpl-t1] The planet's disc, however, is scaled for visibility in log mode, and the spin and the surface features are not modelled. ### Longitude convention The prime meridian of Mercury is tied to the sunlight, not to a landmark. Zero longitude runs through one of the two points on the equator that face the Sun at perihelion and so become the hottest on the planet. When Mariner 10 flew past, that meridian was in darkness, so a small crater named Hun Kal was chosen as the reference and its centre defines the 20° W meridian.[^davies1975] Under the 1970 IAU convention, longitudes on Mercury increase westward, placing the hot equatorial points at 0° W and 180° W and the coolest at 90° W and 270° W.[^usgs-wgccre] The MESSENGER team used east-positive longitudes instead.[^archinal2010] ### Spin-orbit resonance Mercury rotates once every 58.65 days, exactly two-thirds of its 87.969-day orbital period, so it spins three times for every two orbits.[^nasa-fs] The two motions combine to give a solar day of about 176 Earth days, two Mercurian years: a point on the equator has about 88 days of daylight followed by 88 days of night.[^nasa-fs][^planetary-compare] The resonance is stable because the orbit is eccentric. The Sun's tidal torque is strongest at perihelion, and there it acts on a slight permanent asymmetry in Mercury's mass distribution, holding the planet's long axis roughly towards the Sun at each close pass; in a circular orbit only a 1:1 lock would be stable.[^colombo1966] Around perihelion the planet's orbital angular speed briefly exceeds its spin rate, so an observer on the surface would see the Sun stop, move backwards for a few days, then resume its normal course.[^strom2003] At certain longitudes the Sun can rise, sink back, and rise again. The eccentricity of Mercury's orbit is not constant: planetary perturbations drive it chaotically between nearly zero and more than 0.45 over millions of years.[^correia2009][^correia2004] Tidal modelling indicates that Mercury was captured into the 3:2 state very early, within about 10–20 million years of its formation.[^noyelles2014] Long integrations give roughly a 1% chance that a resonance with [[Jupiter]] will raise the eccentricity enough to destabilise the orbit over the next five billion years.[^laskar2008][^laskar2009] ### Advance of perihelion The long axis of Mercury's orbit slowly turns around the Sun. In 1859 Urbain Le Verrier showed that the known planets could not account for all of this precession under [[Newton's_law_of_universal_gravitation|Newtonian gravity]], and suggested an unseen planet or ring of bodies inside Mercury's orbit; the hypothetical planet, Vulcan, was never found.[^leverrier1859][^baum1997] Measured relative to Earth, the observed advance is about 5,600 arcseconds per century, while Newtonian perturbations from the other planets, together with the Sun's slight oblateness, predict about 5,557; the excess is about 43 arcseconds per century (derived).[^clemence1947] [[General_relativity|General relativity]], which treats gravitation as the curvature of spacetime, predicts an extra advance of 42.98 arcseconds per century for Mercury and accounts for the excess.[^gilvarry1953][^brown-mathpages] That is about 0.10 arcsecond per orbit (derived), so the relativistic term alone would take about three million years to turn the orbit through a full circle (derived). The same effect is far smaller for the other planets: 8.62 arcseconds per century for Venus and 3.84 for Earth.[^gilvarry1953][^brown-mathpages] ## Observation Mercury's brightness varies more than any other planet's. Its apparent magnitude ranges from about −2.48 near superior conjunction, when a full disc faces Earth, to +7.25 near inferior conjunction, too faint for the unaided eye; it is brightest when full, because the larger lit area and the opposition surge more than make up for its greater distance.[^mallama2018][^espenak1996] It never appears more than 17.9°–27.8° from the Sun, the range set by where in its eccentric orbit greatest elongation falls.[^walker-fourmilab] In practice, it is seen only briefly in morning or evening twilight.[^menzel1964] Successive inferior conjunctions come about 116 days apart on average, the synodic period.[^nasa-fs] Like [[Venus]] and the [[Moon]], Mercury shows phases in a telescope, though surface detail is faint from the ground. The Hubble Space Telescope cannot observe it at all, because its safety rules forbid pointing so close to the Sun.[^baumgardner2000] Observers in the Southern Hemisphere are favoured: the best morning and evening elongations there fall in seasons when the ecliptic stands steeply to the horizon, so the planet can rise or set hours apart from the Sun.[^rasc2007] Telescopes can also find it in daylight near greatest elongation, provided the Sun is carefully blocked.[^curtis1972] Mercury is also visible during total solar eclipses.[^tezel2003] The explorer shows this geometry from outside: at any year on the slider, Mercury's position relative to Earth and the Sun is the configuration that sets whether it is near elongation or lost in the glare. ## Observation history ### Ancient astronomers The oldest known records of Mercury are in the MUL.APIN tablets, compiled from observations probably made around the 14th century BC; they call the planet "the jumping planet".[^schaefer2007][^hunger1989] Babylonian astronomers of the first millennium BC named it after Nabu, messenger of their gods.[^messenger-cultures] Ptolemy considered whether planets might cross the face of the Sun and concluded that such transits were either too small to see or too rare.[^goldstein1996] In China the planet was the "Hour Star", tied to water in the Five Phases, and several East Asian languages still call it the "water star".[^kelley2004] Hindu tradition named it Budha, the god of Wednesday, a day also linked in Germanic tradition with Woden.[^pujari2006][^bakich2000] In the 11th century al-Zarqālī described Mercury's geocentric deferent as oval, and in the 15th century Nilakantha Somayaji of the Kerala school built a model in which Mercury orbits the Sun.[^samso1994][^ramasubramanian1994] ### Ground-based telescopic research Thomas Harriot and Galileo first turned telescopes on Mercury in 1610; Simon Marius reported its phases in 1612, and Giovanni Zupi's observations of phases in 1639 showed that it orbits the Sun.[^gaab2018][^strom2003] Pierre Gassendi watched a transit of Mercury predicted by [[Johannes_Kepler|Johannes Kepler]] in 1631, the first telescopic observation of a planetary transit.[^strom2003] On 28 May 1737 John Bevis observed Venus pass in front of Mercury, the only such occultation ever recorded.[^sinnott1986] Visual mapping went astray. In the 1880s Giovanni Schiaparelli concluded that Mercury rotates once per 88-day orbit, and Eugène Antoniadi's 1934 maps kept that assumption.[^holden1890][^beatty1999] Radar settled the matter. Soviet scientists led by Vladimir Kotelnikov first bounced a signal off Mercury in 1962, and in 1965 Gordon Pettengill and Rolf Dyce used the Arecibo telescope to measure a rotation period of about 59 days.[^butrica1996][^pettengill1965] Giuseppe Colombo then noted that this is two-thirds of the orbital period and proposed the 3:2 resonance.[^colombo1965] The old maps were not wrong so much as incomplete: at each favourable apparition the same face was turned to Earth.[^colombo-shapiro1965] Later, lucky imaging from Mount Wilson in 2000 resolved regions Mariner 10 had missed, and Arecibo radar mapped most of the planet at 5 km resolution.[^dantowitz2000][^harmon2007] ### Research with space probes Getting to Mercury is expensive in energy. A spacecraft from Earth falls about 92 million km closer to the Sun (derived from the two semi-major axes) and must match an orbital speed of 47.4 km/s against Earth's 29.8 km/s.[^nasa-fs] The [[Potential_energy|potential energy]] released as it falls turns into [[Kinetic_energy|kinetic energy]] that must be shed, and with no atmosphere for aerobraking, only rockets and planetary gravity assists can do it; a Mercury orbit takes more propellant than leaving the Solar System.[^jpl2008][^zacny2015] Mariner 10, launched by [[NASA]], was the first spacecraft to use a gravity assist from one planet, Venus, to reach another, and made three flybys of Mercury in 1974–1975, the closest at 327 km.[^dunne1978][^davies1978] Its geometry kept showing the same lit hemisphere, so less than 45% of the surface was mapped; the spacecraft ran out of fuel on 24 March 1975.[^malik2004][^dunne1978] MESSENGER launched on 3 August 2004, flew past Earth once and Venus twice, made three Mercury flybys in 2008–2009 and entered orbit on 18 March 2011.[^spaceref2005][^jhuapl2008][^messenger2009] Its instruments mapped the planet globally, confirmed the polar ice and measured the surface composition; the mission ended on 30 April 2015 when the spacecraft, out of propellant, struck the surface.[^chang2015] BepiColombo, a joint mission of the European and Japanese space agencies, was launched on 20 October 2018.[^esa2016] It carries two orbiters, one to map the planet and one to study its magnetosphere, and completed its sixth and last Mercury flyby on 9 January 2025 before its scheduled arrival in orbit in 2026.[^esa2007][^bbc2025] ## See also - [[Terrestrial_planet]] - [[Venus]] · [[Earth]] · [[Mars]] - [[General_relativity]] - [[Kepler's_laws_of_planetary_motion]] - [[Formation_and_evolution_of_the_Solar_System]] - [[PORTAL_Solar_System|Solar System portal]] ## Notes Derived numbers are computed from the cited values: the core reaches 2,020 / 2,440 ≈ 0.83 of the planet's radius and fills (0.83)³ ≈ 0.57 of its volume; the distance a spacecraft falls from Earth's orbit to Mercury's is 149.6 − 57.9 ≈ 92 million km; the sunlight ratio between perihelion and aphelion is (69.818 / 46.000)² ≈ 2.30; the excess advance is 5,600″ − 5,557″ ≈ 43″ per century; the relativistic advance per orbit is 42.98″ × (87.969 / 36,525) ≈ 0.10″; and a full relativistic turn takes 1,296,000″ / 42.98″ per century ≈ 30,000 centuries, about three million years. ## References [^nasa-fs]: Williams, D. R. "Mercury Fact Sheet". NASA NSSDCA, last updated 11 January 2024. https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html (fetched 2026-09-18). [^jpl-t1]: JPL Solar System Dynamics. "Approximate Positions of the Planets", Table 1. https://ssd.jpl.nasa.gov/planets/approx_pos.html [^hauck2013]: Hauck, S. A.; Margot, J.-L.; Solomon, S. C.; Phillips, R. J.; et al. (2013). "The curious case of Mercury's internal structure". *Journal of Geophysical Research: Planets* 118: 1204–1220. https://doi.org/10.1002/jgre.20091 [^benz1988]: Benz, W.; Slattery, W. L.; Cameron, A. G. W. (1988). "Collisional stripping of Mercury's mantle". *Icarus* 74: 516–528. https://doi.org/10.1016/0019-1035(88)90118-2 [^pettengill1965]: Pettengill, G. H.; Dyce, R. B. (1965). "A radar determination of the rotation of the planet Mercury". *Nature* 206: 1240. https://doi.org/10.1038/2061240a0 [^colombo1965]: Colombo, G. (1965). "Rotational period of the planet Mercury". *Nature* 208: 575. https://doi.org/10.1038/208575a0 [^prockter2005]: Prockter, L. (2005). "Ice in the Solar System". *Johns Hopkins APL Technical Digest* 26. https://www.jhuapl.edu/content/techdigest/pdf/V26-N02/26-02-Prockter.pdf [^chang2012]: Chang, K. (29 November 2012). "On closest planet to the Sun, NASA finds lots of ice". *The New York Times*, p. A3. https://www.nytimes.com/2012/11/30/science/space/mercury-home-to-ice-messenger-spacecraft-findings-suggest.html [^strom2003]: Strom, R. G.; Sprague, A. L. (2003). *Exploring Mercury: The Iron Planet*. Springer. ISBN 978-1-85233-731-5. https://archive.org/details/exploringmercury00stro [^dunne1978]: Dunne, J. A.; Burgess, E. (1978). *The Voyage of Mariner 10: Mission to Venus and Mercury* (NASA SP-424). NASA History Office. https://history.nasa.gov/SP-424/ [^antoniadi1974]: Antoniadi, E. M. (1974). *The Planet Mercury*. Keith Reid Ltd, pp. 9–11. ISBN 978-0-904094-02-2. [^greeknames]: "Greek names of the planets" (25 April 2010). *Greek Names*. http://www.greek-names.info/greek-names-of-the-planets/ [^smith-planetae]: "Planetae". In *Dictionary of Greek and Roman Antiquities*, pp. 922–923. [^duncan1946]: Duncan, J. C. (1946). *Astronomy: A Textbook*. Harper & Brothers, p. 125. [^jones1999]: Jones, A. (1999). *Astronomical Papyri from Oxyrhynchus*. American Philosophical Society, pp. 62–63. ISBN 978-0-87169-233-7. https://books.google.com/books?id=8MokzymQ43IC&pg=PA62 [^usgs2003]: US Geological Survey (8 May 2003). "Mercury". https://astrogeology.usgs.gov/Projects/BrowseTheGeologicSolarSystem/MercuryBack.html [^lyttleton1969]: Lyttleton, R. A. (1969). "On the internal structures of Mercury and Venus". *Astrophysics and Space Science* 5: 18–35. https://doi.org/10.1007/BF00653933 [^margot2012]: Margot, J.-L.; Peale, S. J.; Solomon, S. C.; Hauck, S. A.; et al. (2012). "Mercury's moment of inertia from spin and gravity data". *Journal of Geophysical Research: Planets* 117. https://doi.org/10.1029/2012JE004161 [^padovan2015]: Padovan, S.; Wieczorek, M. A.; Margot, J.-L.; Tosi, N.; Solomon, S. C. (2015). "Thickness of the crust of Mercury from geoid-to-topography ratios". *Geophysical Research Letters* 42: 1029–1038. https://doi.org/10.1002/2014GL062487 [^sori2018]: Sori, M. M. (2018). "A thin, dense crust for Mercury". *Earth and Planetary Science Letters* 489: 92–99. https://doi.org/10.1016/j.epsl.2018.02.033 [^nrao2007]: Finley, D. (3 May 2007). "Mercury's core molten, radar study shows". National Radio Astronomy Observatory. http://www.nrao.edu/pr/2007/mercury/ [^agu2023]: Genova, A. (17 April 2023). "Scientists find evidence Mercury has a solid inner core". *AGU Newsroom*. https://news.agu.org/press-release/scientists-find-evidence-mercury-has-a-solid-inner-core/ [^nittler2018]: Nittler, L. R.; Chabot, N. L.; Grove, T. L.; Peplowski, P. N. (2018). "The chemical composition of Mercury". In Solomon, S. C.; Nittler, L. R.; Anderson, B. J. (eds.), *Mercury: The View after MESSENGER*. Cambridge University Press, pp. 30–51. https://doi.org/10.1017/9781316650684.003 [^cameron1985]: Cameron, A. G. W. (1985). "The partial volatilization of Mercury". *Icarus* 64: 285–294. https://doi.org/10.1016/0019-1035(85)90091-0 [^weidenschilling1978]: Weidenschilling, S. J. (1978). "Iron/silicate fractionation and the origin of Mercury". *Icarus* 35: 99–111. https://doi.org/10.1016/0019-1035(78)90064-7 [^sappenfield2011]: Sappenfield, M. (29 September 2011). "Messenger's message from Mercury: time to rewrite the textbooks". *The Christian Science Monitor*. https://www.csmonitor.com/Science/2011/0929/Messenger-s-message-from-Mercury-Time-to-rewrite-the-textbooks [^cartwright2011]: Cartwright, J. (30 September 2011). 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"6.2 Anomalous precession". *Reflections on Relativity* (MathPages). https://www.mathpages.com/rr/s6-02/6-02.htm ## External links - NASA Science: Mercury. https://science.nasa.gov/mercury/ - NASA NSSDCA Mercury Fact Sheet. https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html - USGS/IAU Gazetteer of Planetary Nomenclature: Mercury. https://planetarynames.wr.usgs.gov/ - MESSENGER mission (JHUAPL). https://messenger.jhuapl.edu/ - ESA BepiColombo. https://www.esa.int/Science_Exploration/Space_Science/BepiColombo ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Mercury_(planet)) : [Wikitube](https://en.wikitube.io/wiki/Mercury_(planet)) · pinned revision [1374069585](https://en.wikipedia.org/w/index.php?oldid=1374069585) · 2026-09-18 ## Previous hub tags Hubs: `Life_Physics`. 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