Exploration (The Universe) National Aeronautics & Space Administration (NASA) Nine Planets Selology (The Moon) Saturnology (Saturn) Space Research Institute (IKI) (Webpage in Russian) Wikipedia Mercury: Mercury (Wikipedia) Mercury (Nine Planets) Mariner 10 (Wikipedia) Messenger (Johns Hopkins Univ. APL) Messenger (Wikipedia) Venus: Venus (Wikipedia) Venus (Nine Planets) Venus Express (ESA) Venus Express