Last Week’s Lunar Eclipse Seen … From Another Planet

Contributed by
Oct 13, 2014
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Last week’s lunar eclipse was seen by a lot of people—millions, most likely. Certainly a huge number of photos and video were taken of the event as it unfolded over the course of a few hours.

… but none quite like this: The eclipse was observed by the MESSENGER space probe, all the way from Mercury! Normally MESSENGER looks straight down on the tiny world, mapping the terrain that slides underneath it. But engineers saw an opportunity for something neat, so they pointed the camera toward Earth and took 31 images, each two minutes apart, to capture the dance of light:

It’s not often something makes me laugh in delight, but that grainy, lumpy video did. You can see the Earth on the left, all of five pixels wide in the original images (the entire video has been expanded by a factor of two), and the Moon on the right, just barely bigger than a single pixel. The motion of the Moon is too small to detect, but as it passes into Earth’s shadow it dims considerably, disappearing.

Even then, the brightness of the Moon has been multiplied by 25 to make the change more obvious. On Oct. 8, during the eclipse, Mercury was nearly between the Earth and Sun, so to MESSENGER, the Earth and Moon were close to full. But the Earth is bigger and more reflective than the Moon, and would look 50 or so times brighter. I’m not surprised they had to enhance the Moon’s brightness.

MESSENGER was 107 million kilometers (66 million miles) from Earth when it took these images. I think that may be a world universal record for the most distant (terrestrial) lunar eclipse ever seen.

Tip o’ the umbra to Emily Lakdawalla.