NASA successfully launched the InSight mission to Mars this week. This is a great overview of what scientists will be learning about Martian geology.
Previous missions to Mars have investigated the surface history of the Red Planet by examining features like canyons, volcanoes, rocks and soil, but no one has attempted to investigate the planet's earliest evolution - its building blocks - which can only be found by looking far below the surface.
Because Mars has been less geologically active than the Earth (for example, it does not have plate tectonics), it actually retains a more complete record of its history in its own basic planetary building blocks: its core, mantle and crust.
By studying the size, thickness, density and overall structure of the Red Planet's core, mantle and crust, as well as the rate at which heat escapes from the planet's interior, the InSight mission will provide glimpses into the evolutionary processes of all of the rocky planets in the inner solar system.
In terms of fundamental processes that shape planetary formation, Mars is a veritable "Goldilocks" planet, because it is big enough to have undergone the earliest internal heating and differentiation (separation of the crust, mantle and core) processes that shaped the terrestrial planets (Earth, Venus, Mercury, Moon), but small enough to have retained the signature of those processes over the next four billion years. Within its own structural signature, Mars may contain the most in-depth and accurate record in the solar system of these processes.
The InSight mission will follow the legacy of NASA's Mars Phoenix mission and send a lander to Mars, which will delve deeper into the surface than any other spacecraft - to investigate the planet's structure and composition as well as its tectonic activity as it relates to all terrestrial planets, including Earth.