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Emily LakdawallaApril 16, 2018

Moon Monday: Deimos

There are not very many good pictures of Deimos. Here's a new Viking composite that I just put together. What a weird little world, shaped like a lost baby molar, with its flat or even concave south pole.

Deimos from Viking 2 Orbiter

NASA / JPL / Emily Lakdawalla

Deimos from Viking 2 Orbiter
Deimos is poorly explored. This is one of few color portraits, taken by Viking 2 on August 10, 1977. This is a highly processed image: the reseaux have been painted out; channels warped to align each other (because of apparent rotation of Deimos from one image to the next); and a blue channel has been synthesized from red- and clear-filter data.

The outer and smaller of Mars' two moons is really, really tiny, only 15 kilometers across at its widest point. (That makes it similar in size to the asetroid Gaspra, Pluto's moon Kerberos, and smaller than any of the lumpy moons of Saturn for which we have good photos from Cassini except the even smaller Methone.) It orbits close to Mars, only about 20,000 kilometers above the surface, but it's still far from any of the orbiters that we have mapping Mars from their low circular orbits. So the best pictures that we have of Deimos are still the ones from Mariner 9 and the Viking orbiters. (Viking has more detail, but Mariner 9 got the far side.)

It was pretty easy for me to find the data for this one because, several years ago, I made myself a cheat sheet: a summary of all the Viking orbiter images of Deimos. This is it; this is the data set. There may be a few other images but they're all tiny. You can see the original images for the composite above in the third row on the left. Now that I have this summary, I can grab a set of images and have fun processing without going back into the Planetary Data System. Any of you could, too -- have at them!

Every Viking Orbiter image of Mars' moon Deimos

NASA / JPL / Emily Lakdawalla

Every Viking Orbiter image of Mars' moon Deimos
Mars' outer and smaller moon Deimos appears in 111 Viking Orbiter images gathered between August 16, 1976, and October 18, 1978. Targeting Deimos was a challenge, and it was often cut off at the edge of the frame.

I posted some processing notes on Twitter:

Because I have this composite (posted here: ) it's easy for me to grab sets to try to make new color composites. The color pic I posted is made of a clear, a red, and a green-filter image.

— Emily Lakdawalla (@elakdawalla) April 16, 2018

There are still some color fringes, especially at the edge of the moon on the left side, because they don't all align perfectly. To be completely honest, I just got out the paintbrush and painted that orange streak black. Sometimes there's no option.

— Emily Lakdawalla (@elakdawalla) April 16, 2018

And then I subjectively adjust the levels of the red, green, and blue channels to give Deimos the reddish color of the very space-weathered body that it is. So this is an art project, not a scientific representation, but one that's meant to be representational.

— Emily Lakdawalla (@elakdawalla) April 16, 2018

Read more: pretty pictures, data art (was amateur image processing), NASA Mars missions before 1996, Deimos

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
Read more articles by Emily Lakdawalla

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