atmosphere The envelope of gases surrounding Earth or another planet.

basin (in geology) A low-lying area, often below sea level. It collects water, which then deposits fine silt and other sediment on its bottom. Because it collects these materials, it’s sometimes referred to as a catchment or a drainage basin.

carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.

cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall.

climate The weather conditions that typically exist in one area, in general, or over a long period.

climate change Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

colleague Someone who works with another; a co-worker or team member.

computer program A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.

density The measure of how condensed some object is, found by dividing its mass by its volume.

ecology A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

ecosystem A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra.

environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).

forest An area of land covered mostly with trees and other woody plants.

greenhouse gas A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.

lidar (short for light detection and ranging) A tool to measure the shape and contour of the ground from the air. It bounces a laser pulse off a target and then measures the time (and distance) each pulse traveled. Those measurements reveal the relative heights of features on the ground struck by the laser pulses.

matter Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."

NASA Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

physical (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).

planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, the object must be big enough to have pulled neighboring objects into the planet itself or to have slung them around the planet and off into outer space.

quadrillion A very big unit of measure equal to 1,000 trillion. It would be written with a 1 followed by 15 zeros.

remote sensing Collecting data about an object or area from a distance, such as by using satellite cameras to take images of Earth.

satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.

terrestrial Having to do with planet Earth, especially its land. Terra is Latin for Earth.

tropics The region near Earth’s equator. Temperatures here are generally warm to hot, year-round.