A
- Aerosol
- Tiny bits of dust, smoke, salt or pollution floating in the air. They can block sunlight and help clouds form.
- Asteroid
- A rocky object that orbits the Sun, much smaller than a planet. Most are in a belt between Mars and Jupiter.
B
- Biodiversity
- The variety of all living things in a place: plants, animals, fungi and tiny microbes.
- Biomass
- The total amount of living material, like the wood and leaves in a forest. Measuring it shows how much carbon plants store.
C
- Carbon dioxide (CO₂)
- A gas that people and animals breathe out and that burning fuel releases. Plants take it in, and too much of it in the air warms the planet.
- Coronal mass ejection (CME)
- A huge cloud of charged gas thrown out from the Sun. If it hits Earth it can cause auroras and disturb satellites and power grids.
D
- Deorbit
- To bring a satellite or piece of space junk down out of orbit on purpose, usually so it burns up in the atmosphere.
E
- Ecosystem
- A community of living things and the place they live, like a reef or a forest, all depending on each other.
G
- Greenhouse gas
- A gas, like carbon dioxide or methane, that traps heat in the air around Earth, the way a greenhouse keeps plants warm.
I
- Infrared
- A kind of light our eyes can't see that we feel as heat. Special cameras use it to see warm objects and gases.
K
- Kelp
- Large brown seaweed that grows in cool ocean water and forms underwater forests full of sea life.
L
- Lagrange point
- A spot in space where the pull of the Sun and Earth balance, so a spacecraft can stay in place with little fuel. L1 sits between Earth and the Sun.
M
- Magnetosphere
- Earth's invisible magnetic shield. It steers most of the Sun's charged particles away from our planet.
- Mangrove
- A tree that grows in salty water along tropical coasts. Its tangled roots protect shores from waves and shelter young fish.
- Methane
- A greenhouse gas that traps much more heat than carbon dioxide over a few decades. It leaks from oil and gas sites, landfills and farms.
- Microplastics
- Pieces of plastic smaller than 5 millimeters, about the size of a grain of rice or smaller. They come from bigger plastic breaking apart.
O
- Orbit
- The curved path an object takes as it travels around a planet, moon or star, like a satellite circling Earth.
- Ozone
- A gas high in the sky that blocks harmful ultraviolet rays from the Sun. Near the ground, ozone is a pollutant.
P
- Phytoplankton
- Tiny plant-like living things that drift in water and use sunlight to make food. They make much of the oxygen we breathe and feed ocean life.
R
- Radar
- A tool that sends out radio waves and listens for the echoes. From space it can see the ground through clouds, day or night.
- Reentry
- When a spacecraft or piece of space junk falls back into Earth's air. The friction makes it very hot, so most small objects burn up.
S
- Salt marsh
- A coastal wetland of grasses that floods with salty tide water. It soaks up storm surges and stores carbon in its mud.
- Satellite altimetry
- Measuring the height of the sea or land from space by timing how long a radar or laser pulse takes to bounce back.
- Seagrass
- Flowering plants that grow underwater in shallow seas, forming meadows that shelter animals and store carbon.
- Solar wind
- A steady stream of charged particles flowing out from the Sun in every direction.
- Synthetic aperture radar (SAR)
- A radar on a moving satellite that combines many echoes into one sharp picture, as if it had a giant antenna.
T
- Telescope
- An instrument that collects light (or other energy) to see faraway things more clearly.