AI Insight
Stickney Crater is the largest impact crater on Phobos, Mars' moon, measuring over 9 kilometers across—nearly half the diameter of Phobos itself. The impact that created this crater was so powerful it nearly destroyed the small moon. Enhanced-color images from the Mars Reconnaissance Orbiter's HiRISE camera reveal surface features including material slides down crater walls, freshly exposed bluish surfaces near the rim, and mysterious grooves across the surface that may relate to tidal stresses or the original impact.
Why it matters
Understanding Stickney Crater provides insights into impact physics on small celestial bodies and the structural integrity of asteroid-like moons. The mysterious grooves and tidal stress patterns on Phobos help scientists understand the dynamics of moons in close orbit around their parent planets, which is relevant for future missions and our understanding of solar system formation.
Understand the Science
APOD
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
Stickney Crater
Explanation: Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet’s moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth’s gravity, streaks suggest loose material slid down inside the crater walls over time. Light bluish regions near the crater’s rim could indicate a relatively freshly exposed surface. The origin of the curious grooves along the surface is mysterious but may be related to tidal stresses experienced by close-orbiting Phobos or the crater-forming impact itself.
Tomorrow’s picture: farside
| Date: | October 9, 2026 |
|---|---|
| Credit: | HiRISE, MRO, LPL (U. Arizona), NASA |
| Authors & editors: | Jerry Bonnell, Cecilia Chirenti, Robert Nemiroff, Keighley Rockcliffe |
| A service of: |
ASD at NASA / GSFC, NASA Science Activation & Michigan Tech. U. |
Source: APOD: 2026 October 9 – Stickney Crater