Astronomy Picture of the Day - Phobos: Doomed Moon of Mars

NASA ^ | 25 Jan, 2026 | Image Credit: NASA, LPL (U. Arizona), MRO, HiRISE

[MtnClimber]

Explanation: This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These Martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of our Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the robotic Mars Reconnaissance Orbiter, which can image objects as small as 10 meters. But Phobos orbits so close to Mars - about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon - that gravitational tidal forces are dragging it down. In perhaps 50 million years, Phobos is expected to disintegrate into a ring of debris.

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

[MtnClimber]

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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

🪐 🌟 🌌 🍔

[Steely Tom]

In Arthur C. Clarke's story The Sands of Mars, nuclear engineering is used to ignite Phobos, thereby turning it into a tiny sun. The light generated thereby is used to facilitate the rapid spread and growth of a genetically-engineered plant that extracts oxygen from the martian surface cover; in that way, Mars's atmosphere is regenerated, to make the planet habitable by humans.

An engineer who explains the process says, of the ignition of Phobos, "we used a simple meson-resonance reaction."

[Gasshog]

So in 50 million years Mars will have a ring and One Moon

[No name given]

Wow.

[kawhill]

“Explanation: This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic.” Thank you, that is a reason I hang out here a bit.

[Doctor Congo]

When I was young I did some calculations for Phobos. I do not remember how I did it but the results were:

- If you were standing on Phobos you would see Mars taking up one third of the sky from horizon to horizon.

- You could not throw a football off the moon but you could hit a golf ball all the way to Mars.

- I forget how high you could jump but it was high. That would be scary.

[dljordan]

“That’s no moon”

[chickenlips]

Sure looks a lot like James Carville. Probably smarter too.

[telescope115]

The Martian Chronicles sci-fi by Ray Bradbury, made into a mini-series for 1980 with Rock Hudson. Mission to Mars, movie with Gary Sinise, 2000, and The Martian, 2015, starring Matt Damon.

All good. Any others?

[Steely Tom]

- You could not throw a football off the moon but you could hit a golf ball all the way to Mars.

- I forget how high you could jump but it was high. That would be scary.

Nice calculations! That sounds like college-level work. If you did it in high school, very impressive!

You want low gravity? Check this out:

The OSIRIS-REx spacecraft collected a bit of asteroid Bennu by means of a jet of pressurized nitrogen. It shot a few grams of N₂ into Bennu to stir up some particles for collection.

That blast of N₂, lasting a couple seconds, displaced enough of Bennu's surface to leave a crater 26 feet in diameter.

Bennu is about 500 meters across. It's gravitational field is so weak that it's not really a solid mass; it's more like a clump of rocks and dust that are just hanging together as they travel through space.