The Red Planet

Thanks to the Mars Global Surveyor and its Laser Altimeter we now know the vertical profile of the planet, to a precision rivaling that for Earth.

With a clever blend of radio science and remote sensing we can even look below the surface to see the thickness of the Martian crust.

And on that surface in 1997, "Sojourner" the first rover on Mars became a mechanical geologist, rolling up to a series of rocks and sniffing out their chemistry.