Seismic and Gravitational Studies

What is the evidence? Measurements of how seismic wave velocities vary with depth beneath a planetary surface; measurement and mapping of a planetary body’s gravitational field

What does it tell us? Seismic waves provide information about motion within the crust (earthquakes, moonquakes, marsquakes); the internal structure of a planet, asteroid, or Moon, including the presence and properties of a core. Gravitational field maps provide information about features of surfaces, such as mountains, craters, and thickness of the crust.

Key limitations: Access—while there is an extensive network of seismometers on Earth, placing them on other planetary bodies is challenging (currently on Moon and Mars); orbital limits—gravitational field sensors require remote sensing by orbiting spacecraft

Example: Marsquakes

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Aboard NASA’s Mars InSight lander is a seismometer that measures vibrations from marsquakes and meteorite impacts. Watch the video to learn more about InSight’s Seismic Experiment for Interior Structure (SEIS) instrument and what scientists hope to learn from the data it gathers.