The Lunar Farside: A Science And Exploration Imperative
Neither humans nor robots have ever landed on the Moon’s farside. This is surprising given that the Moon is the closest planetary body to Earth and the farside has a land area nearly 4 times larger than that of the United States. Yet, after 60 years of scientific exploration beyond Earth, the farside remains untouched. The lunar farside presents a unique opportunity for science and exploration. It contains the oldest impact crater in the inner solar system – the South Pole Aitken (SPA) Basin. A human-assisted sample return mission to the SPA basin, a priority of the Planetary Science Decadal Survey, will provide a unique test of the lunar cataclysm hypothesis which posits that the Moon and Earth were severely bombarded by asteroids and comets ~4 billion years ago. A major rearrangement of planet distances relative to the Sun and the first single-cell life on Earth both occurred at about this same time. Connecting these pieces using the SPA basin is a scientific imperative. Equally important, the farside is a unique preserve for low frequency radio astronomy and cosmology. The farside is free of Earth-based radio-frequency interference (RFI) and ionospheric effects. An array of radio telescopes will allow us to matchlessly probe the first generation of stars and galaxies using the redshifted hyperfine 21-cm line of neutral hydrogen, to image radio emission from coronal mass ejections for the first time, and to study space weather in extrasolar planetary systems to investigate suitability for life. In this talk, we will discuss locations on the farside that are best suited for these science goals. For example, radio arrays must be far enough from the limb and/or deep within craters to reduce diffraction effects from RFI by factors of ~80 dB. We will discuss regions such as the Schrödinger impact basin and the Tsiolkovsky crater as candidate landing sites to accommodate science and exploration goals.