Moons - Definitions

Full list of definitions for the FutureLearn course Moons.

  • Created by: zelahl32
  • Created on: 15-11-16 15:40
A disc of gas and dust around a young planet within which moons may grow.
Accretionary disc
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Small particles of dust-rich glassy breccias formed when micrometeorites strike the lunar regolith.
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The percentage of incident light reflected by an object.
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Having an irregular, non-repeating structure at the atomic level.
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A class of rock-forming hydrous aluminosilicate mineral with characteristic double-chain structure.
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A material that has properties that are different in one direction from another.
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An example of a plagioclase feldspar.
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The point at which an orbiting is furthest from the object it orbits.
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The point at which the Moon or any other Earth satellite is furthest from Earth.
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A rocky or metallic body smaller than a planet. Most are found in the ______ Belt between Mars and Jupiter.
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The circular belt of asteroids that orbit the Sun between Mars and Jupiter.
Asteroid Belt
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The mean distance between the Sun and the Earth ( about 1.5x10^8 km).
Astronomical unit
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Lava that is rich in pyroxene, olivine and plagioclase feldspars.
Basaltic lava
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The exposed crust when any soil or regolith has been removed.
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Two objects orbiting a common centre of mass.
Binary system
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A rock-forming hydrous aluminosilicate mineral with characteristic sheet structure and strong cleavage.
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The splitting of light into two rays by anisotropic materials, which causes characteristic colour schemes when observed in thin sections between crossed polarisers.
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Coarse grained clastic rock.
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A circular depression more than 1km across resulting from a volcanic eruption. Excavation may be mainly by explosive ejection or by collapse into the space left inside after magma has been erupted.
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Rich in carbon.
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Descriptor term to denote a distinctive area of broken-looking terrain.
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The formation of organic matter using chemical energy.
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Thin strands of clouds, named after the Latin word '___' for a ringlet or curling strand of hair.
Cirrus clouds
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A rock formed from fragments of pre-existing rocks.
Clastic rock
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Coming together of fragmented material, for example under its own gravity.
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An icy/carbonaceous body from the outer Solar System typically kilometres or tens of kilometres in size, which occasionally visits the inner regions at great speed.
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Circular objects having a common centre but different radii.
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The tendency of heated fluid to expand, become less dense and rise buoyantly through surrounding cooler liquid.
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Term used to describe a class of terrain seen on Uranus' moon Miranda.
Corona (1)
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Part of the solar atmosphere, less dense and warmer than lower levels of the atmosphere; visible without instrumentation only during total eclipse.
Corona (2)
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Magma generated from icy material, as opposed to silicate magma produced by the melting of rock.
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Volcano that erupts liquid or vapour e.g. water or methane, instead of molten rock.
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Having a regular repeating structure at the atomic level.
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Process by which glass becomes crystalline.
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Sorting of material by gravity according to density.
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An area covered by dunes.
Dune field
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Coarse-grained igneous rock consisting largely of olivine.
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Long narrow tube of lava that cuts through earlier structures, often vertically.
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The plane at which the Earth orbits the Sun.
Ecliptic plane
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C2H6 - under terrestrial conditions, a colourless, odourless gas closely related to methane.
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A moon in orbit around an exoplanet.
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A planet in orbit around a star other than the Sun.
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Faulting resulting from extension of the ground surface, in contrast to compressional faulting such as thrusts.
Extensional faulting
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One of Saturn's rings. They were named in order of their detection, so the spatial order is D,C,B,A,F,G and E-ring, going outwards.
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A break in the crust of a planet through which volcanic material may emerge.
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A process occurring in a cooling liquid where the crystallisation of one phase changes the composition of the remaining liquid, which in turn changes the composition of later-forming crystals.
Fractional crystallisation
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A rock easily crumbled or reduced to dust in the hand.
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Device for detecting tiny vibrations of the ground.
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The shape of the Moon between half and full moon.
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A down-dropped trough of terrain bounded by faults.
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When a spacecraft uses the gravity of a planet to alter its path and speed.
Gravitational slingshot manoeuvre
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Using the gravity of a planet or moon to change the trajectory of a spacecraft.
Gravity-assist manoeuvre
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Compounds with metal-halogen composition such as sodium chloride (common salt).
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A compound consisting exclusively of hydrogen and carbon.
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The molecular grouping (OH) that is characteristic of alcohols.
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Speeds in the range of several to several tens of km/s.
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Electromagnetic radiation of longer wavelength than visible but not as long as microwaves.
Infrared radiation
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Space beyond the Sun's influence.
Interstellar space
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To remove at least one electron from an atom.
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Two atoms having the same atomic number but different mass numbers.
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Measuring the age of a sample by the ratio of the amount of decay product to the surviving amount of its parent isotope.
Isotopic dating
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The apparent oscillations of a moon as seen from its parent body, if the moon rotates once per orbit but its orbit is not exactly circular.
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A linear fissure that is the source of an eruption, as opposed to a circular (pipe-like) vent.
Linear vent
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Rock types classified by their origin, formation and mineral composition.
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A simple antenna on a spacecraft that does not need to be steered, but which is much less sensitive than a parabolic antenna.
Low-gain antenna
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Molten rock, usually containing dissolved gas, in the interior of a planet or moon.
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On planets and larger moons, the region between core and crust.
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Latin for sea, applied to relatively smooth and dark areas on the Moon, now known to have been flooded with lava. Also used to refer to the large methane lakes on Titan.
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A small rocky or metallic body flying through space.
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CH4 - under terrestrial conditions, a colourless, odourless gas but sometimes liquid on the surface of Titan. Can form an ice in the outermost regions of the Solar System.
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Tiny meteorites, sometimes defined as less than 2mm in diameter.
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Term used to describe a micrometeorite when still in space i.e. before impact onto a moon or planet.
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Shapes of objects. When writing of terrain features such as craters this means their three-dimensional shapes, taking into account their outline and their topography.
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10^-9 m
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Describes electromagnetic radiation that is of wavelength just longer than visible.
Near-infrared wavelength
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The solid state of nitrogen found on some of the extremely cold moons in the outer Solar System.
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Splitting of heavy nuclei into fragments with release of energy.
Nuclear fission
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The core of an atom consisting of protons and neutrons.
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Mineral containing silicon, iron and magnesium.
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When two moons have their orbital periods in an integer ratio e.g. 2:1 or 3:2.
Orbital resonance
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Pressure is higher than outside. In a geological context refers to the fluid or gas inside fractures or voids of a rock.
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Dish-like antenna on a space probe used to transmit and receive signals. To communicate to Earth it must be pointed towards the Earth, so it has to be steerable.
Parabolic antenna
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A small probe designed to be dropped from a spacecraft so that it impacts into a moon's surface, from where it can gather data.
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The point at which an orbiting body is closest to the object it orbits.
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The point at which the Moon or any other Earth satellite is closest to Earth.
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Production by plants of organic compounds using carbon dioxide and fuelled by solar energy.
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A series of silicate minerals found in many igneous rocks.
Plagioclase feldspars
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A small asteroidal body formed early in Solar System history.
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The creation and subsequent movement of distinct plates in the crust of a planet.
Plate tectonics
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Breccias containing many different types of rock or mineral fragment.
Polymict breccias
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The body whose gravity keeps a satellite in its orbit.
Primary body
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Term describing an orbit of an object round the Sun, or a moon around a planet, in which the orbital motion is in the same direction as the rotation of the Sun or the planet.
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A disc of gas and dust around a star from which planets may form.
Protoplanetary disc
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Adjectives referring to fragments (as opposed to lava flows) produced by an eruption.
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Mineral containing silicon, iron, calcium and magnesium.
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Production of an image from radar data.
Radar imaging
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The disintegration of unstable nuclei.
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The mixture of impact-generated fragmental material that develops on the surface of any airless planet or moon.
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Describes an object's spin that is in the opposite direction to its orbital motion.
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A moon whose orbit is close to one of a planet's rings and whose repeated gravitational influence helps to maintain the shape of the ring.
Shepherd moon
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A type of volcano that has been built almost entirely by low viscosity lava flows erupted from near its summit.
Shield volcano
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Any rock containing silicate minerals, which are based around silicon oxide.
Silicate rock
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Instrument for measuring the wavelengths of spectral lines.
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The study of the composition of something from analysis of the light emitted or reflected.
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Electromagnetic signature of an element or compound.
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The study of sequences of rock strata and their relationships in time and space.
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The acceleration experienced by an object when dropped near the surface of a planet or moon.
Surface gravity
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Equalisation of the rotation period of a body (its' day) with its orbital period (a 'year').
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The boundary between the sunlit and unilluminated hemispheres of a planet or moon.
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The tendency of an object to heat up, because of internal friction, when pulled out of shape by tidal forces.
Tidal heating
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The lie of the land
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The size of a crater formed by an impact measured before it has been widened by outwards slumping of its walls.
Transient crater size
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Electromagnetic radiation of shorter wavelength than visible but not as short as X-rays.
Ultraviolet radiation
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Said of a body in which gravity has not sorted material according to density.
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Tendency of fluids to resist flow as a result of internal friction.
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Hypothetical asteroids orbiting the Sun inside Mercury's orbit.
Vulcanoid asteroids
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The state of water when it is below 0 degrees Celsius
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An instrument measuring fluorescene caused when elements are bombarded by high-energy X-rats, used to determine elemental composition of rocks.
X-ray fluorescence spectrometer
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Other cards in this set

Card 2


Small particles of dust-rich glassy breccias formed when micrometeorites strike the lunar regolith.



Card 3


The percentage of incident light reflected by an object.


Preview of the front of card 3

Card 4


Having an irregular, non-repeating structure at the atomic level.


Preview of the front of card 4

Card 5


A class of rock-forming hydrous aluminosilicate mineral with characteristic double-chain structure.


Preview of the front of card 5
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