Acid: In chemistry, a substance that may have a sour taste, makes blue litmus paper turn red, and can react with a base to make salt.
Ammeter: A device used to measure electrical current, which is measured in amperes (A, or amps).
Anorthosite: The predominant rock of the lunar highlands.
Apogee: A point in a satellite's orbit where it is furthest from the Earth.
Arc: A line in the sky from horizon to horizon which extends 180 degrees.
Astronomy: The scientific study of the universe, including the solar sytem, stars and galaxies.
Atmosphere: An envelope of mixed gases that surround a celestial body such as a planet, moon, or star. An atmosphere is held to the body by the body's gravity.
Atmospheric Pressure: A force over a given area that is caused by the weight of an atmosphere.
Axis: An imaginary line through the centre of a planet or satellite around which it rotates.
Base: A substance that may have a bitter taste, feels soapy, and neutralizes acids.
Blood pressure: The pressure of blood on the walls of blood vessels.
Breccia: A rock made from mineral fragments cemented together by the heat of meteoroid impact.
Chromatography: A method of separating a mixture of compounds by the use of a porous material.
Composition: The chemical makeup of an object.
Compound: A substance made by combining two or more parts or elements; water is a chemical compound made from hydrogen and oxygen.
Coordinate System: A system used to identify locations on a graph or grid. Latitude and longitude are an example of a coordinate system.
Core: The central region of a planet or moon frequently made of different material than the surrounding regions (mantle and crust). Earth and the Moon are thought to have cores of iron and nickel.
Condensation: A change of state from gas to liquid.
Crater: A basin resulting from the collision of an object with a planetary surface.
Dehydrated: The state a substance is in when moisture has been removed from it; too much heat can dehydrate the body.
Density: The mass of a substance for a given volume.
Diameter: The distance across a circle through its centre. Also, the distance through a sphere, measured through the centre of the sphere.
Diastolic: A measurement of the amount of pressure on the walls of blood vessels when the heart is at rest.
Diffraction: The bending of light as it passes through a small slit or opening. When we study the diffraction of sunlight, we see a rainbow of colours.
Ellipse: A conic section; the curve of intersection of a circular cone and a plane cutting completely through the cone.
Equatorial orbit: An orbit around the plane of the equator.
Evaporation: A change of state from liquid to gas.
Fog: A cloud at ground level.
Force: That which can change the momentum of a body. Numerically, the rate at which the body's momentum changes.
Geosynchronous orbit: An equatorial, circular orbit approximately 36,000 km above the centre of the Earth in the plane of the equator.
Gravity: The natural force of attraction that exists between all bodies in the universe.
Latitude: The angular distance north or south from the Earth's equator measured in degrees on the meridian of a point: equator being 0 degrees and the poles 90 degrees North and 90 degrees South.
Lava: Molten rock that erupts to Earth's surface through a volcano or a fissure.
Longitude: The angular distance east or west, between the meridian of a particular place on Earth and that of the Prime Meridian (located in Greenwich, England) expressed in degrees or time.
Lunar: Relating to the Moon
Maria: Low areas on the Moon that appear dark and smooth. Maria are formed by ancient lava flows.
Mass: The amount of material present in an object. In an Earth environment this quantity is often directly compared to weight. Mass is an intrinsic property of the object.
Meteorite: A solid fragment of some planetary body that has passed through the Earth's atmosphere and landed intact on its surface.
Meteoroid: A small, solid body moving through space in orbit around the Sun.
Motion: Movement of an object in relation to its surroundings.
NASA: National Aeronautics and Space Administration, a United States federal agency.
Orbit: The path of an object around another object, e.g., planets moving around the Sun.
Parallel: Two lines running side by side at an equal distance apart. Railroad tracks run parallel to each other.
Particulates: Solid particles suspended in a gas or liquid.
Payload: The cargo (scientific instruments, satellites, spacecraft, etc.) carried by a rocket.
Perigee: The place in the orbit of an earth satellite where it is closest to the center of the Earth.
pH: A scale from 1 - 10 that specifies how acidic or alkaline a substance is.
Pigment: The colouring of a particular object or substance.
Planet: Any of nine solid, nonluminous bodies revolving about the Sun.
Planetary Geology: The study of the processes and history associated with the solid, rocky objects of the solar system.
Polar axis: The axis of rotation of the Earth; also, an axis in the mounting of a telescope that is parallel to the Earth's axis.
Prism: A piece of transparent material that separates the colours of sunlight into a rainbow or spectrum.
Probe: A spacecraft, with no humans aboard, designed to study conditions on or near a planet.
Propulsion: The act of moving an object and maintaining its motion.
Pulse Rate: The number of times a heart beats per minute in a person's body.
Radiation: A mode of energy transport whereby energy is transmitted through a vacuum; also, the transmitted energy itself, either electromagnetic or corpuscular.
Reaction: A movement in the opposite direction from the imposition of an action.
Regolith: A powdery soil layer on the Moon's surface caused by bombardment by meteoroids.
Respiration rate: The number of breaths a person makes per minute.
Revolution: The motion of one body around another.
Rocket: A device propelled by ejection of matter, especially by the high velocity ejection of the gaseous combustion products produced by internal ignition of solid or liquid fuels.
Satellite revolution: The time from one perigee (the point of an elliptical orbit path where a satellite is closest to the Earth) to the next.
Satellite: A body that revolves about a larger one; for example, a moon of a planet.
Solar Activity: Phenomena of the solar atmosphere associated with sunspots, plagues, and related phenomena.
Solar system: The system of the Sun and the planets, their satellites, the minor planets, comets, meteoroids, and other objects revolving around the Sun.
Space debris: Debris from satellites and space vehicles, as well as natural objects like meteorites and planetary particles that travel through the Solar System.
Space shuttle: A partially reusable space transportation system that can carry people and cargo; built to replace launch vehicles that could only be used once.
Space station: An orbiting space laboratory on which people could live and work for several years or more.
Spacecraft: Vehicle capable of travelling in outer space and in earth orbit.
Spectroscope: A device used for separating light into component colours for analysis.
Sphygmomanometer: A device used in conjunction with a stethoscope to measure a person's blood pressure.
Star: A self-luminous sphere of gas.
Sun: The star about which the Earth and other planets revolve.
Sunspot: A temporary cool region in the solar photosphere that appears dark by contrast against the surrounding hotter photosphere.
Tectonics: The process that forms planetary features such as continents, mountains, and faults.
Trajectory: The path of a projectile or other moving body through space.
Transceiver: A radio that uses many of the same components for transmitting and receiving signals.
Universe: The totality of all matter and radiation and the space occupied by same.
Velocity: A vector that denotes both the speed and direction a body is moving.
Viscosity: Having a relatively high resistance to flow.
Volcano: An opening in the Earth's crust where molten lava, gases and ash are ejected.
Weight: The force with which the Earth's (or any celestial body's) gravity pulls down on something.