Dark Side of the Moon

Craters_at_the_Moon_s_south_poleBoth the far side and near side of the Moon receive sunlight during a month. Still, Pink Floyd fans may be cheered to know that there are parts of the Moon that never see the Sun. There is a dark side of the Moon. The Moon’s axis has a tilt of 1.5º which causes the bottoms of some craters to be in permanent shadow.

This picture was assembled from images taken during summertime in the Moon’s southern hemisphere by the Advanced Moon Imaging Experiment on ESA’s SMART-1 spacecraft and shows a crater-riddled region around the lunar south pole. It is made up of around 40 individual images taken between December 2005 and March 2006, and covers an area of about 500 x 150 km.

Image Credit: ESA

A View From Mars

earth-from-mars-hiresA telescope in orbit around Mars took this view of Earth and its Moon, showing continent-size detail on the planet. The image combines two separate exposures taken in November, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. The images were taken to calibrate HiRISE  using the known value of reflectance for the Earth-facing side of the Moon. The exposures used to make this composite image were processed separately to optimize detail visible on both Earth and the Moon. The Moon is much darker than Earth and would barely be visible if shown at the same brightness scale as Earth.

The combined view retains the correct positions and sizes of the two bodies relative to each other. The distance between Earth and the Moon is about 30 times the diameter of Earth. Earth and the moon appear closer than they actually are in this image because the observation was planned for a time at which the Moon was almost directly behind Earth as seen from Mars so that the Earth-facing side of the Moon would be visible.

The reddish feature near the middle of the face of Earth is Australia. Mars was about 205 million km from Earth when the images were taken, so nude sunbathers are not visible in this image.

Image Credit: NASA

The Earth Seen From Space

One of the most famous images of Earth was taken by Voyager 1 when it was 6 billion km from home. The Earth is a single pixel in that picture called The Pale Blue Dot. Voyager 1 was just about 12,000,000 km above Mt. Everest when it took this picture of the Earth and the Moon on 18 September, 1977. The Moon is on the far side of the Earth in this picture which shows East Asia, the Western Pacific, and part of the Arctic. Mt. Everest in hidden from view on the night side of the Earth.

Image Credit: NASA

You Are Here

earthmoon_cassini_960This is the Earth-Moon system as seen by the Cassini spacecraft orbiting Saturn in the outer Solar System. Earth is the larger of the two spots near the center; the Moon is to its lower left. This raw, unprocessed image shows several streaks that are not stars. They are cosmic rays that struck the digital camera while it was taking the picture.

Image Credit: NASA


This video takes us around the Moon and shows how it is illuminated not only by the brilliant light of the Sun but also by light reflected from the Earth. The trip starts on the side facing away from Earth where part of the surface is brightly illuminated by the Sun but the rest is totally dark. Moving around the Moon, the Earth rises, and its reflected bluish light illuminates the Moon’s surface. This dull glow is the earthshine. (You can clearly see it from Earth when the Moon appears as a crescent in the evening or morning sky.) When the Sun emerges from behind the Moon, the brilliant crescent is seen, but the earthshine is still faintly visible.

Video Credit: ESO