Final answer:
Observing Venus from Earth is challenging due to thick clouds that hide its surface, necessitating the use of radar mapping to study its geology.
Step-by-step explanation:
It is difficult to learn about Venus from Earth-based observations alone due to its impenetrable cloud cover which reflects about 70% of the sunlight, hiding its surface features. To study Venus's surface, scientists utilize radar mapping to penetrate the clouds, revealing a geologically diverse planet with features such as the large continent Aphrodite.
For comparison, Mars offers more visible features such as dark markings and polar caps, but it is only 11% of Earth's mass, while Venus is nearly identical in size and mass to Earth. Venus's surface, unlike Earth, does not undergo significant erosion and deposition, allowing geological features to remain remarkably preserved. This difference highlights the diverse planetary evolution of Venus, Earth, and Mars.