Glossary

417 words used in the labs.

Find a term from the labs, understand the process behind it, and see how it appears in the landscape. Each entry connects an explanation with a real observation and a model you can explore.

Term

Terrestrial planet

Also written: Rocky planet

A planet with a predominantly rocky composition and a solid surface, such as Mercury, Venus, Earth or Mars. The category describes composition rather than habitability. These planets differ greatly in atmosphere, temperature and geological activity.

What to look for

Apollo 17's Blue Marble, 7 December 1972. Earth's axial tilt changes the angle and duration of sunlight over the year.

Related labs

Solar system →

The fully sunlit Earth showing Africa, Arabia, Antarctica and swirling clouds in the Apollo 17 photograph.

Explore further with USGS water glossary · USGS volcano glossary · NPS glacial geology · NASA Earth facts. Photograph acknowledgements are collected on the Image credits page.