Never visible from Earth, the "dark side" of the Moon is less mysterious in this GIF below.
Captured by NASA’s Earth Polychromatic Imaging Camera (EPIC) in July, the furthest side of the Moon is in full view as it crosses in front of the Earth.
— NASA (@NASA) August 5, 2015
The Moon is tidally locked to our planet, meaning the same face of the Moon is always positioned towards Earth and hence we never see the far, or "dark," side.
Beginning regular observations this September, EPIC, a four-megapixel camera and telescope, is mounted onto the Deep Space Climate Observatory (DSCOVR) satellite, orbiting 1.5 million kilometers (1 million miles) away from Earth.
In a partnership between NASA, the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Air Force, this distant location between the Earth and the Sun allows the satellite to optimally monitor real-time solar wind changes for accurate space weather alerts and forecasts.
Even more mysteriously, the fate of this space probe is unknown. After taking 29 images of the Moon, which covered 70% of its far side, the space probe possibly burned up in the Earth’s atmosphere in 1960, but it may also have survived in orbit until 1962 or even later.