Emily LakdawallaFeb 08, 2019

Looking Back at MU69

Hamburger Patty-Shaped World

The New Horizons team released this stunning crescent view of 2014 MU69 today. I love crescent views so much. They mean so much.  You have to be farther from the Sun than a place in order to get a crescent view. New Horizons did it; it's beyond this distant solar system world, as it's beyond so many others.

MU69's crescent
MU69's crescent New Horizons took the images for this crescent view of 2014 MU69 from a position 8,862 kilometers beyond it. To see such a thinly lit crescent so far from the Sun required long exposures, and the original images were blurred. Team members stacked 10 exposures and processed the result to remove the motion blur and present this sharp view. NASA / JHUAPL / SwRI

This photo was from an observation that shows MU69 moving against background stars. That observation has revealed something remarkable and confusing and amazing: MU69's shape isn't that of a snowman, it's flat, like two hamburger patties smushed together. (Yes, "smush" is a technical term.) Who ordered this?? Nobody, that's who.

Shape model for 2014 MU69
Shape model for 2014 MU69 The two lobes of 2014 MU69 are roughly circular in cross-section, so the simplest assumption was that they were spherical. Following New Horizons' flyby, it became clear that they are very non-spherical. The larger lobe is extremely flat, like a hamburger, and the smaller lobe is also squashed. The blue dotted lines indicate the uncertainty in the shape estimate; it could be less flat than the figure depicts, but still very flat. NASA / JHUAPL / SwRI

This is just bonkers, and is going to be, I think, the major scientific accomplishment of the MU69 flyby. Geophysicists did not predict this. Back to the drawing board! Isn't that fun?

You can read more about the discovery and observations at the New Horizons website, but I want to take the rest of this post to enjoy other weird-shaped space crescents.

New Horizons has taken a couple of other good ones. Here's a crescent Nix. Not many pixels, but a funky looking crescent!

Crescent Nix
Crescent Nix This is a stack of 16 images taken by New Horizons about 3 hours after closest approach. Nix's outline is very faint but clear. The resolution of this image, which has been enlarged by a factor of 3 from the original, is 310 meters per pixel, and the phase angle is 158 degrees. NASA / JHUAPL / SwRI / Emily Lakdawalla

Or how about this crescent Io? Io has a hat. (It's actually not a hat, it's a fiery fountain of lava. Do not touch Io's hat.)

Io's crescent
Io's crescent New Horizons captured this photo of Io with its Long Range Reconnaissance Imager (LORRI) as it sped away from the Jupiter system on March 3, 2007 at 06:11 UTC. NASA / JHUAPL / SwRI

Here's a cool crescent Ceres from Dawn. I love how the extreme lighting really shows that Ceres is on the edge of being a lumpy, not round, world.

Skinny crescent Ceres
Skinny crescent Ceres Dawn took this photo of Ceres from the dwarf planet's night side on April 29, 2015. It has a phase angle of 155.6 degrees. NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

Let's contrast that with a photo of Enceladus. Enceladus is half the diameter of Ceres and so much smoother! I love the specular (mirror-like) reflection off the edge at upper right. Smooth as ice. Smooth and ice.

Enceladus’ crescent in natural color (17 January 2005)
Enceladus’ crescent in natural color (17 January 2005) Cassini captured the images for this portrait of Enceladus on 17 January 2005, through red, green, and blue filters. NASA / JPL-Caltech / SSI

Let's see, where else can we go? How about some lumpy worlds. Here's a crescent Phobos.

Crescent Phobos from Mars Express, 25 May 2007
Crescent Phobos from Mars Express, 25 May 2007 Mars Express captured this view of a crescent Phobos on May 25, 2007. The view is looking down on the northern hemisphere, with the equator toward the top. A bright splash of material on the upper right limb is the west rim of the giant crater Stickney. ESA/DLR/FU Berlin (G. Neukum) / Emily Lakdawalla

How about crescent Hyperion?

High-Resolution Mosaic of a Crescent Hyperion, 25 August 2011
High-Resolution Mosaic of a Crescent Hyperion, 25 August 2011 As Cassini approached Hyperion for a close encounter on 25 August 2011, it snapped a three-image mosaic of the sponge-like moon at a crescent phase. The mosaic did not quite cover the entire visible crescent, so a wide-angle image (with a resolution 10 times lower than the other images) was used to fill in a small area on the "nose." NASA / JPL-Caltech / SSI / mosaic by Emily Lakdawalla

Here's a crescent Lutetia (this is one of two asteroids Rosetta visited on the way to Churyumov-Gerasimenko).

Lutetia's crescent, in color
Lutetia's crescent, in color A parting view of Lutetia as Rosetta sped away on July 7, 2010. ESA / MPS / UPD / LAM / IAA / RSSD / INTA / UPM / DASP / IDA / Daniel Machacek

Speaking of Rosetta, here's comet 67P. Comets have a slightly different way of doing the crescent thing.

Backlit comet
Backlit comet Single frame enhanced NavCam image taken on 27 March 2016, when Rosetta was 329 km from the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale is 28 m/pixel and the image measures 28.7 km across. ESA / Rosetta / Navcam

Especially when we smack them really hard, intentionally.

Deep Impact "lookback" image of Tempel 1
Deep Impact "lookback" image of Tempel 1 This "lookback" image was captured by Deep Impact's high-resolution imager as it receded from its flyby of comet Tempel 1 on 4 July 2005. The bright spot is not an incandescent flare; it represents dust in the ejecta curtain spraying out from the comet, which is backlit by the Sun. NASA/JPL-Caltech/UMD

I hope you've enjoyed all these lookback views! There are a lot more in our image library!

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