Iwa

Iwa was a planet in a single-star system. It was the location of a kind of penal colony which punished people for their potential crimes. It was also the site of the first contact between the Doctor and Humans. It was the location where Susan obtained the name "Susan", and the Doctor was first called "the Doctor".

Topography
Iwa had a barren surface, more rock than vegetation. In fact, when the Doctor's TARDIS landed on the planet, its chameleon circuit chose to turn the vehicle's exterior into a boulder, out of deference to the craggy landscape.

Meteorology
Rain was relatively uncommon on the planet, and when it came, it did so extraordinarily briefly. As a result, the air remained fairly saturated and humid. The sky itself was blue, indicating similar chemical composition and light refraction to Earth.