Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 April 10
The featured image shows the permanently shadowed
region at the Moon's South Pole. The picture is a composite
of many lunar images taken from many illumination angles 
revealing which parts are never in direct sunlight.
Please see the explanation for more detailed information.

Shadows at the Moon's South Pole
Image Credit: NASA, Arizona State U., Lunar Reconnaissance Orbiter

Explanation: Was this image of the Moon's surface taken with a microscope? No -- it's a multi-temporal illumination map made with a wide-angle camera. To create it, the Lunar Reconnaissance Orbiter spacecraft collected 1,700 images over a period of 6 lunar days (6 Earth months), repeatedly covering an area centred on the Moon's south pole from different angles. The resulting images were stacked to produce the featured map -- representing the percentage of time each spot on the surface was illuminated by the Sun. Remaining convincingly in shadow, the floor of the 19-kilometre diameter Shackleton crater is seen near the map's centre. The lunar south pole itself is at about 9 o'clock on the crater's rim. Crater floors near the lunar south and north poles can remain in permanent shadow, while mountain tops can remain in nearly continuous sunlight. Useful for future outposts, the shadowed crater floors could offer reservoirs of water-ice, while the sunlit mountain tops offer good locations to collect solar power.

Tomorrow's picture: ISS Sunspot


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