The terrae are very rough and heavily cratered. Craters are still abundant on the maria, but there are far fewer than on the terrae. Mercury Mercury looks much like the Moon. There are some smooth areas that may be lava plains, but it's hard to tell. Mars Mars has a greater diversity of surface features than Mercury or the Moon.
Impact craters are still abundant, but volcanoes and lava plains are more evident.
There are also huge scars formed by crustal extension and erosion. Tree-like channel networks resemble drainage networks, suggesting water was once at or near the surface. There are some impact craters, but far fewer than the Moon, Mercury, or even Mars. Vast dark portions of the radar images indicate smooth plains, likely lava. Distinct lava flows are visible, as are many volcanoes.