An image from NASA/JPL-Caltech depicting a capsule starting to slow down in the Martian atmosphere. All we see is the outer structure, which seems mostly to be made of metal. But inside…
The rover (Curiosity) and descent stage of the spacecraft are inside the aeroshell consisting of the backshell and heat shield. This friction with the atmosphere before the opening of the spacecraft’s parachute will accomplish more than nine-tenths of the deceleration of the entry, descent and landing phase.
I found the image on Wikimedia Commons, but you can read more about in the NASA mission pages multimedia library.