Astronomy Picture of the Day - Saturn's Iapetus: Painted Moon

NASA ^ | 5 Jul, 2026 | Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

[MtnClimber]

Explanation: What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as snow. To help better understand this unusually tinted moon, in 2007 NASA directed the robotic Cassini spacecraft then orbiting Saturn to swoop within 2,000 kilometers. Pictured here, from about 75,000 kilometers out, is the hemisphere of Iapetus that is always trailing. A large impact crater seen in the south spans 500 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. A leading hypothesis is that the dark material is mostly a form of carbon-rich soil leftover from when relatively warm but dirty ice sublimates. An initial coating of this dark material may have been effectively painted on by the accretion of meteor-liberated debris from other moons.

---

TOPICS: Astronomy; Astronomy Picture of the Day; Science
KEYWORDS: apod; nasa

[MtnClimber]

To be added or removed from the Astronomy Picture of the Day ping list please send me a request via "Private Reply" (Mail).

For more detail go to the link and click on the image for a high definition image. You can then move the magnifying glass cursor then click to zoom in and click again to zoom out. When zoomed in you can scan by moving the side bars on the bottom and right side of the image.

[MtnClimber]

[MtnClimber]

Pinging the APOD list

🪐 🌟 🌌 🍔

[MtnClimber]

It looks like it is saying “Ouch, you gave me a black eye just because I took a bite of your cheeseburger”.

[Red Badger]

[Ronaldus Magnus III]

There are many images of the moon Iapetus without the darker materials. Those images look very much like the Empire’s Death Star.

[ComputerGuy]

A moldy orange is the first thing I thought of.

[Carry_Okie]

So where is the 1:4:9 monolith?

Clarke’s book puts it on “Japetus,” while the movie has it hanging in space.

[Red Badger]

There’s more than one monolith. They are guardians of primitive but sentient life forms................

[BenLurkin]

bttt

[jmacusa]

That thing kinda looks like Jupiter's moon Io.

[Carry_Okie]

There’s more than one monolith. They are guardians of primitive but sentient life forms................

The book had one on the moon, one on Japetus, and I recall dimly that there was yet a third on another world to which Dave Bowman had been transported. They were a portal of sorts bypassing limits of linear space-time.

[No name given]

Wow.

[blueunicorn6]

It looks like the top of a mushroom.

Many cheeseburgers have delicious sliced mushrooms on them.

[null and void]

Was the dark side facing the sun during a solar micronova event?

[MtnClimber]

I think you are right.

[Red Badger]

There was one on Europa where some primitive life form was evolving. That’s why we were supposed to stay away from Europa, but the did not listen.............

[SkyDancer]

Looks like some big whatever hit it ....

[Carry_Okie]

There was one on Europa where some primitive life form was evolving.

Don't remember that in Clarke's version of 2001. It was over 50 years ago I read that book. Never read Childhood's End.

[Red Badger]

It was in the second sequel, 2061: Odyssey Three....