The impeller made out of cast material in many cases may be called rotor, also. It is cheaper to cast the radial impeller right in the support it is fitted on, which is put in motion by the gearbox from an electric motor, combustion engine or by steam driven turbine.
Earth remains the only known planet to host life, due to a unique combination of factors. However, continued monitoring of alien worlds might one day change that, by finding other planets that share these attributes or by discovering other ways that life has found to blossom in the universe.
Mars is a planet that shows climate change on a large scale. Although its atmosphere used to be thick enough for water to run on the surface, today that water is either scarce or non-existent. The atmosphere today is also too thin to easily support life as we know it, although life may have existed in the ancient past.