Andy's Wiki
Solar System Scratchpad

[Boiler Plate]
Solar System Planets

The innermost, fastest, and smallest solar system planet, known to the ancients as two different planets. It is composed mostly of a large iron core. It rotates three times for every two orbits around the Sun. Its daytime side is one of the hottest places in the solar system, while its night side is one of the coldest. One of the only rocky bodies known to have its own magnetic sphere. Has a minimal atmosphere and no moon. Visited by the Mariner 9 spacecraft three times and is currently orbited by Messenger. Several other international missions are planned.

Mercury Places in the News[]

Impact Craters:

  • Caloris Basin - The largest impact basin on Mercury and one of largest in Solar System. Discovered by Mariner 10, which only imaged half of it. First image of Mercury sent by Messenger was centered on this basin. As opposed to lunar basins, which are filled with dark material, Caloris is filled with light plains, which has not been explained yet. MESSENGER found titanium oxide in a region northwest of here.
  • Rembrandt Basin - The second largest impact basin on Mercury discovered by MESSENGER during its second flyby. Formed 3.9 BYA (young for a large basin). Lava only flowed in the central region, unlike most similar basins. A unique formation of spoked ridges also appears in the basin. The largest fault on the planet runs through this basin. The only basin with its original impact floor exposed which have not been obliterated by subsequent vulcanism.
  • Rachmaninoff Basin - A large double-rimmed impact basin on Mercury, 180 miles in diameter. One of the youngest seen. First seen in its entirety during Messenger's third flyby. Its floor has been resurfaced with the most recent volcanism detected on the planet so far and the youngest volcanic surface, probably under 2 billion years old. These plains differ in color than the surrounding area. A volcanic vent was discovered to the north of the crater. The impact may have risen the temperature of the mantle area to the melting point, which spurred the vulcanism. Fourth crater found (after Caloris, Rembrandt, and Raditladi) to have extensive tectonic features, which are of unknown origin.


  • Degas Crater - Crater on Mercury initially observed by Mariner 10. As it cooled, cracks formed across it.
  • Debussy Crater - A large crater on Mercury whose rays extend across much of the southern hemisphere. It was first discovered by radar observations from the Goldstein observatory and initially dubbed Feature A. It was first photoed by Messenger during a flyby and subsequently given a name. It was the dominant feature in the first photo from the Messenger probe from orbit.
  • Matabei Crater - A crater on Mercury with rare dark rays. It was visible in Messenger's first photos sent from orbit.
  • Hokusai Crater - Large, young, and bright-rayed crater on Mercury. Initially detected with radar at the Goldstone Observatory, it was dubbed Feature B and originally thought to be a volcano.


  • Northern Volcanic Plains - Volcanic plains covering the northern polar regions of Mercury. About the size of the continental United States. Massive volcanic eruptions are thought to have blanketed the area about 3.7 billion years ago, burying craters under several kilometers of lava.

Mercury Features[]

Interior Layers[]

  • Mercury/Core - Iron core of Mercury. Much larger proportionally than other planets (about 60% of its mass), making Mercury an Iron planet. Originally thought to have cooled early on, doubts occurred when Mariner 9 showed it had a magnetic field. Proven to be molten in 2007. Significant amount of a lighter element, such as sulfur, must be present in order to prevent its cooling. The magnetic field strength is about 1% that of Earth, so it must not have completely solidified. It has strong north-south assymetry, causing a lop-sided magnetic field.
  • Mercury/Mantle - The mantle is about 500-700 km thick, consisting of Silicates surrounding Mercury's core and beneath its crust. It is thought that it does not rise and fall in convective patterns like on Earth and other larger planets, so it may not have cooled as quickly, enabling volcanism to persist over halfway through its lifespan.
  • Mercury/Crust - Crust of Mercury. Lacks weathering from liquids or an atmosphere and covered, maintains ancient craters, and covered in grey regolith like the Moon. Formed more like Mars than the moon in that heavy vulcanism was involved. Better shielded from Solar radiation than the Moon due to Magnetosphere. Comprised of three terrains, smooth plains, intermediate terrain, and low-reflective material. Thought to have contracted as the planet shrunk, forming rifts and tectonics, which could also represent a process of plate forming that never got going.

Surface Terrain[]

  • Mercury/Smooth Plains - Key component of Mercury's terrain, covering about 40% of its surface, located between later craters and evenly distributed around the planet. Likely volcanic in origin, it is the oldest surface known on the planet, predating the heavily cratered terrain. Appears to have covered up some older craters and younger than the Caloris Basin. Unlike volcanic plains of the Moon, it is the same base color as the older inter-crater plains. Characterised by rupes which criss-cross the plains, perhaps due to planetary compression.
  • Mercury/Intermediate Terrain - Heavily cratered plains on Mercury. The same albedo as the smooth plains.
  • Mercury/Low Reflectance Material - Areas of Mercury dominated by Low Reflective Material (LRM). Thought to have been dug out of interior, as it has been ejected in the forms of rays of several craters.

Surface Forces[]

  • Mercury/Volcanoes - Responsible for much of the smooth terrain on Mercury, the largest constituent of its surface. Evidence for volcanism confirmed during Messengers first two flybys. Evidence for earlier volcanism dating to half the age of the solar system was found during Mercury's third flyby. Now dormant, it once involved sulfurous compounds.
  • Mercury/Tectonics - Forces on Mercury thought to have subsided in the past. Perhaps due to crustal compression, it caused rifts to appear throughout Mercury's smooth plains regions.

Surface Features[]

  • Mercury/Craters - Craters caused by impacts on Mercury. These can be cut through by scarps (possibly compressed in the process) or covered over by volcanic ejecta. Some have long bright rays, while others have long dark rays. The transitional diameter of craters (10-12 km) between simple (bowl-shaped) and complex craters (central peaks and ridges) is twice that of Mars, despite the fact that surface gravity at both planets are roughly the same. The fact that the average impact speed is 2-3 times greater than that of Mars may be a contributing factor.
  • Mercury/Eternal Shadow Craters - Craters near Mercury's poles that are deep enough so that sunlight never penetrates them. Possibly contain water ice which has remained there over geological time periods. Messenger's altimeter has revealed that they are deep enough to harbor frozen water.
  • Mercury/Lobate Scarps - High cliffs on Mercury. Areas where one block of the planet's crust has been thrust over another, in what appears to be planet-wide contraction. When they cut through craters, the craters are halved or squeezed horizontally.
  • Mercury/Pits - Rimless irregular pits that cluster around to form patchy deposits on some crater floors. These may be evidence of a recent volatile emission, such as a sulfur compound.

Dynamic Features[]

  • Mercury/Hot Pole - The side of Mercury that the Sun is directly pointing at. Messenger must be careful not to look directly at it to avoid frying its instruments.

External Environment[]

  • Mercury/Atmosphere - Thin surface bound exosphere of Mercury, sometimes referred to as its atmosphere. Its main constituents are Hydrogen and Helium (believed to originate from solar winds) and atomic Oxygen (believed to originate from the surface). Sodium and to a lesser degree Potassium are found near the poles. Calcium is centered around the equator. Magnesium was first detected by Cassini during a flyby. Originally speculated about when it was thought to be tidally locked, found to be mostly absent by Mariner 9. Molocules are constantly escaping to space, forming a tail away from the Sun due to heat, so must be replenished somehow.
    • Mercury/Tail - A tail of atoms escaping from Mercury's gravity due to irradiation by the Sun. Its composition and intensity varies by season. Comprised mostly of Sodium, but Calcium has also been detected. Its length was much diminished during Messenger's third flyby as Mercury was traveling at a different speed along its orbit than it was during the first two flybys. Earthbased observations show that the tail extends more than a thousand planetary radii.
  • Mercury/Magnetic Field - Magnetic field of Mercury, the only other known internally generated magnetic field of any terrestrial planet other than Earths. Its strength is 1% that of Earth and weaker than that of Ganymede. Generated by a partially molten core in the region where the core and the mantle meet. Its magnetic equator is significantly north of the physical equator (20% of radius), so that its strength is stronger in the northern hemisphere than the southern one. The only other planet that has this characteristic is Saturn, which is off only by less than 1%. The southern polar magnetic cap, where field lines are open to the interplanetary medium are much larger than those in the north. One theory is that it is beginning to flip.
    • Mercury/Magnetosphere - Protective sphere around Mercury due to its magnetic field about the size of the Earth. It varies considerably depending on where Mercury is on its orbit and solar activity. This variance leads to variable protection of molecules in its exosphere and causes them to vary. Stronger on the northern hemisphere than the southern one, allowing more solar wind to strike the South pole than the north one. Its boundary is the Magnetopause. It is rather leaky, much so than the Earth on stormy days, magnetic tornadoes offer paths for solar wind to directly impact the surface.
    • Mercury/Magnetic Tornadoes - Spiraling magnetic field lines within Mercury's magnetosphere. "Flux Transfer Events" are those originating from the Magnetopause, while Plasmoids are those originating from within the Magnetotail. They allow solar wind particles direct access to its surface, where they collide with the surface and kick up material, which replenishes Mercury's atmosphere. Mercury's distance from the sun can only account for 30% of these events, some undetermined property is responsible for the rest.
      • Mercury/Flux Transfer Events - Magnetic tornadoes originating in Mercury's magnetopause and terminating at its surface. These are magnetic field lines that coil and penetrate the magnetosphere, allowing a path for particles from the sun to follow to strike Mercury's surface. These "storms" are much more powerful than those at Earth. Mercury's atmosphere may be replenished from the Sun via these storms.
      • Mercury/Plasmoids - Magnetic Tornadoes that originate from within Mercury's Magnetotail.
    • Mercury/Magnetic Substorms - Magnetic substorms, consisting of a build up of magnetic energy Mercury's Magnetic tail. First seen during Messenger's third flyby. The intensity are ten times that of the ones found at Earth. The duration was about two to three minutes, about fifty times as rapid as those on Earth.
    • Mercury/Magnetopause - Outermost layer of Mercury's magnetic field. Kelvin-Helmholtz waves were detected during Messenger's first flyby.
    • Mercury/Magnetotail - Magnetic region of Mercury streaming away from the Sun on the daytime. Length varies depending on how far Mercury is from the sun, from 10 Mercury radius to 100. Plasmoid Magnetic Tornadoes can originate from here. Powerful magnetic substorms were also observed in this region.
    • Mercury/Energetic Particle Events - Energetic particle bursts first detected by the Mariner 10 probe, but not detected by Messenger during its flybys. Messenger found that these are electrons instead of ions, at occur at modest latitudes and occurred regularly through each of its orbits. One possible explanation is that they are caused by a double layer in the magnetic field or by the rapidly changing magnetic field structure.



  • Mercury/Iron - One of the main constituents of Mercury's molten core. Likely bonded with a lighter element, such as Sulfur, in order to stay molten. Not completely molten in the core. Suspected to exist in trace amounts in the atmosphere, but has not been detected yet.
  • Mercury/Sulfur - Likely contained in Mercury's core and bound to its Iron in order to prevent it from solidifying. Ten times as much Sulfur was detected on the surface than on Earth or the Moon. It is thought to be a component in explosive vulcanism.
  • Mercury/Magnesium - Element thought to exist on the surface of Mercury. It was detected in much higher abundancies by Messenger during a flyby than expected (similar to that of Calcium). It is evenly distributed over the globe, for some reason, unlike Calcium (near the equator), which is a puzzle. Also differently distributed than Sodium.
  • Mercury/Calcium - Element found in Mercury's atmosphere in equatorial regions, and in higher concentrations near sunrise than sunset, which oddly persisted during all three Messenger flybys while most of the rest of the environment was ever-changing. It is a mystery why Sodium and Magnesium are distributed differently. Also detected in Mercury's tail. Emissions from ionized Calcium were observed near the equatorial plane in the exosphere by Messenger during its third flyby.
  • Mercury/Sodium - Element found in Mercury's atmosphere in polar regions. Its distribution is different than that for Calcium and Magnesium. It's also main constituent in Mercury's tail, which was much diminished in length during Messenger's third flyby due its its different speed than during the first two.
  • Mercury/Aluminum - Surface element on Mercury, less abundant compared to Silicon than the Earth, in favor of more Potassium. It is suspected of existing in Mercury's atmosphere.
  • Mercury/Silicon - Surface element on Mercury. It is suspected of existing in Mercury's atmosphere.
  • Mercury/Hydrogen - Most abundant element in Mercury's exosphere and one of first detected by Mariner 10. Thought to originate from solar winds. Some exit via channels in the magnetic fields.
  • Mercury/Potassium - Surface element on Mercury, ten times or more abundant than that of Earth or the Moon. Second most abundant element in Mercury's exosphere and one of first detected by Mariner 10, thought to originate from the surface.
  • Mercury/Helium - One of first elements detected in Mercury's atmosphere by Mariner 10. Thought to originate from solar winds. Some exit via channels in the magnetic fields.


  • Mercury/Water - Water ice is thought to be frozen in Mercury's eternal shadow craters like the Moon. Smooth areas detected by Earth-based radar are an early evidence. Messenger found that the shadow craters are sufficiently deep to trap water ice there.

Geological History[]

  • 3.9 BYA - Rembrandt Basin, one of the younger basins in the solar system, is created.
  • 3.7 BYA - Massive eruptions in the Northern Volcanic Plains bury craters under several kilometers of lava.
  • Under 2 BYA - Rachmaninoff Basin, one of the youngest impact basins is created, which softens up the underlying mantle, sparking volcanism in the region.

Mercury Webpages[]

Mercury in the News[]

Earth Observations in the News[]

Mercury Has Molton Core (May 2007)[]

See Mercury/Core, Mercury/Magnetic Field, Mercury/Iron, Mercury/Sulfur

Dark Halos Discovered (Mar 2008)[]

MESSENGER in the News[]

First Flyby of Mercury (Jan 2008)[]

2nd Flyby of Mercury (Oct 2008)[]

2nd Flyby of Mercury Science Results (May 2009)[]

Magnesium Detected in Mercury's Atmosphere[]
See Mercury/Atmosphere, Mercury/Tail, Mercury/Magnesium, Mercury/Calcium, Mercury/Sodium, Mercury/Iron, Mercury/Aluminum, Mercury/Silicon
Mercury Surface Characterized[]
See Mercury/Crust, Mercury/Regolith, Mercury/Volcanoes, Mercury/Smooth Plains, Mercury/Intermediate Terrain, Mercury/Low Reflectance Material, Mercury/Tectonics
Magnetic Tornadoes Discovered (May 2009)[]
See Mercury/Magnetic Tornadoes, Mercury/Plasmoids, Mercury/Flux Transfer Events, Mercury/Atmosphere, Mercury/Magnetosphere, Mercury/Magnetopause, Mercury/Magnetotail, Sun/Interplanetary Magnetic Field, Sun/Solar Wind, Venus/Atmosphere, Earth/Atmosphere, Mars/Atmosphere
Remarkable Formations in Rembrandt Basin[]
See Rembrandt Basin

Third Flyby of Mercury (Sep 2009)[]

Year of the Solar System (Feb 2011)[]

See also Comet 103P/Hartley 2, Sun, Comet 9P/Tempel 1, Mercury, Vesta, Ceres, Jupiter, Moon

Third Flyby Science Results (Jul 2010)[]

Spacecraft entered safety mode before all observations could be completed.
Ion Emissions and Unusual Distribution in Exosphere Detected[]
See Mercury/Exosphere, Mercury/Ion Emissions, Mercury/Tail, Mercury/Sodium, Mercury/Calcium, Mercury/Magnesium
New Information on Magnetic Substorms[]
See Mercury/Magnetic Substorms, Mercury/Magnetotail, Earth/Substorms
Evidence of Younger Volcanic Activity[]
See Mercury/Volcanoes, Rachmaninoff Basin, Mercury/Mantle

Photo of Most Planets From Near Mercury (Feb 2011)[]

See Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Looking Ahead to Orbital Insertion (Feb 2011)[]

See Caloris Basin

Lunar and Planetary Conference Briefing Approaching (Feb 2011)[]

Getting Ready to Enter Mercury Orbit (Mar 2011)[]

About to Enter Mercury Orbit (Mar 2011)[]

Enters Mercury Orbit (Mar 2011)[]

Normal Operations Confirmed (Mar 2011)[]

First Image From Orbit (Mar 2011)[]

See Debussy Crater, Matabei Crater, Hokusai Crater
First Image From Orbit Photoessay[]
See also Venus, Mars, Jupiter, Saturn, Uranus, Neptune

100 Orbits Made (May 2011)[]

Mercury Orbit Science Results (Jun 2011)[]

Science Highlights

Clusters of Pits Resolved on Crater Floor Bottoms[]
See Mercury/Pits
Surface Elements Characterized[]
Significant amounts of volatiles, sulfur and potassium, found on surface, in contrast with the Moon or Earth. This supports ground based claims sulfide minerals are present and may have contributed to past volcanism. Rules out solar wind blast away Mercury's outer layer theory.
See Mercury/Crust, Mercury/Sulfur, Mercury/Potassium, Mercury/Volcanoes, Mercury/Aluminum, Mercury/Potassium
Northern Volcanic Plains Characterised[]
Northern hemisphere is low-profile. Overall topographic deviation seen to date exceed 9 km. Huge low-lying volcanic plains exist at the north polar regions, about the size of the continental United States.
See Northern Volcanic Plains
Craters Near Poles Deep Enough to Harbor Frozen Water[]
Craters at northern poles appear to be deep enough to support trapped water ice theory.
See Mercury/Eternal Shadow Craters, Mercury/Water
Magnetic Field Characterized[]
Confirmed bursts of energetic particles in Mercury's magnetosphere are a continuing product of the interaction of Mercury's magnetic field with the solar wind. Magnetic field stronger in North than South, indicating something odd about its core. This leaves the south polar regions more exposed to solar particles.
See Mercury/Magnetic Field, Mercury/Magnetosphere, Mercury/Core
Energetic Particle Events Due to Electrons[]

Messenger's Cost Saving Measures and Example (Jun 2011)[]

See Europa, Moon for GRAIL, Titan for Titan Mare Explorer

Transition Diameter of Craters is Twice that of Mars (Jul 2011)[]

see Mercury/Craters, Mars/Craters

Messenger Marks 7th Anniversity of Launch (Aug 2011)[]

BepiColombo in the News[]

Launch Summer 2014, ESA
Composed of three parts Mercury Transfer Module, Mercury Planetary Orbiter (MPO, ESA), Mercury Magnetosphere Orbiter (MMO, JAXA), and the canceled Mercury Surface Element (MSE)

Large Space Simulator Upgraded for BepiColombo (Jan 2011)[]

Mercury Magnetosphere Orbiter in the News[]

JAXA, Launched with BepiColombo

Japan to launch Mirror Protected Spacecraft (Jul 2010)[]

Mercury Studies in the News[]

Mercury Naturally Smaller than Earth and Venus (Jan 2008)[]

Mercury Factoids[]