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Surreal Lunar Orbit Footage From Doomed GRAIL Mission

The views expressed are those of the author and are not necessarily those of Scientific American.

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On December 17th 2012 two small spacecraft called Ebb and Flow punched into the lunar surface at over 3,700 miles an hour.

This ended the year long mission of NASA’s Gravity Recovery and Interior Laboratory (GRAIL). The twin spacecraft spent most of this time orbiting the Moon’s surface at a scarily low altitude of about 31 miles, sweeping in tandem above the dusty terrain never more than 140 miles apart from each other.

Gravity map of the Moon (Credit: NASA/JPL-Caltech/MIT/GSFC)

Microwave telemetry between the spacecraft, the Earth, and the application of basic geometry let GRAIL monitor the distance between Ebb and Flow to a precision of about a tenth of a micron – half the width of a human hair.

As with any planet or satellite the Moon’s gravitational field is not perfectly symmetrical. Variations in the density and height of material produce tiny variations in the gravitational acceleration felt by other objects. By sensing Ebb and Flow’s varying movement in orbit a detailed map of the lunar gravity field was constructed. With a knowledge of the topographic features on the surface this can be turned into the equivalent of a medical tomographic reconstruction of the lunar interior – and it’s lumps and bumps.

The data is amazing, but GRAIL had one last gift to give. In the days leading up to their crash on the lunar surface the spacecraft returned imagery from their ever lowering orbits.

This is the quite surreal and beautiful timelapse footage taken by Ebb as it skimmed across part of the northern terrain of the Moon’s far side at an altitude of only 6 miles on December 14th 2012. Enjoy.

Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His books include Gravity's Engines (2012) and The Copernicus Complex (2014) (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Whail1 1:24 pm 01/11/2013

    I believe a human hair is quite a bit more than 2 microns.

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  2. 2. alan borky 1:41 pm 01/11/2013

    Caleb almost shockingly at times what we see resembles a close up tracking shot of sea foam along a stretch of beach on a very clear night lit by a full moon. Presumably the almost melted white chocolate smoothness of the surface is an artefact of the level of focus used and the intensity of the brightness control? Or is this part of the moon really that smooth [even if only from very fine dust]?

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  3. 3. jtdwyer 2:09 pm 01/11/2013

    Wow! What a wonderful video. I kept looking for, but never found, the obelisk (ref. “2001: A Space Odyssey).

    I do think it’d have been cuter if the satellites had been named Ebb & Flo…

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  4. 4. Fanandala 2:30 pm 01/11/2013

    I measured between 20 and 60 microns.
    I think it is confusing and stupid to mix the imperial measure of miles with the metric measure of microns. Since this is a scientific publication, could they not stick to SI units. Its about time that even the US enters the 21st century.

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  5. 5. Caleb A. Scharf in reply to Caleb A. Scharf 2:34 pm 01/11/2013

    alan borky: nice visual analogy. I think there is a lot of image saturation here. Smoothness is in part an illusion – at 6 miles up and this camera resolution things tend to look pretty smoothed out, even if they’re fields of boulders a few meters across, we’re really just seeing the larger scale topography.

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  6. 6. Caleb A. Scharf in reply to Caleb A. Scharf 2:35 pm 01/11/2013

    Re hair width/units. Mea culpa. Agreed that the use of units is inconsistent.

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  7. 7. ferncanyon 4:10 pm 01/11/2013

    Didn’t they get any pictures right up until impact? It would be interesting to see it heading towards the mountain.

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  8. 8. PeterT 6:15 pm 01/11/2013

    Please SA – Why doesn’t your e-mail button work??

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  9. 9. didoxdido 6:57 am 01/22/2013

    This is a rework of the GRAIL’s moon shots along with gravity maps created from the data acquired, enjoy it ;)

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