Stickney (crater)

Stickney is the largest impact crater on Phobos, the inner satellite of Mars. This impressive crater measures about 9 kilometers (5.6 miles) in diameter, covering a large part of the moon's surface. Craters like Stickney form when objects from space crash into a planet's surface or its moons, creating deep pits and changing the landscape. Studying Stickney helps scientists learn more about the history of impacts in our solar system and the geological processes of small celestial bodies.

Naming

The Stickney crater is named after Chloe Angeline Hall Stickney, the wife of the astronomer who discovered Phobos. Her support was very important to her husband’s work. The crater received its name in 1973 after images from the Mariner 9 spacecraft were studied by a group led by Carl Sagan.

Formation

There are two ideas about when the Stickney crater formed, depending on when Phobos started orbiting Mars. If Phobos has been orbiting for 4.3 billion years, then Stickney formed 4.2 billion years ago. If Phobos has only been orbiting for 3.5 billion years, then Stickney formed 2.6 billion years ago. The impact that created Stickney sent out a lot of material, called ejecta, which escaped Phobos's gravity and went into orbit around Mars. This material stayed there for up to 1000 years before either falling back to Phobos or creating smaller craters on the moon. Most of the smaller craters on Phobos were made by these secondary impacts.

Main article: ejecta

Physical features

Stickney is the largest crater on Phobos, a moon of Mars, and it is about 9 kilometers (5.6 miles) wide. Grooves and chains of smaller craters appear to spread out from Stickney. One idea is that these grooves were formed by the powerful impact that created Stickney, which may have almost broken Phobos apart. Other ideas include that the grooves were made by material thrown up from impacts on Mars, by the pull of Mars's gravity, or even by boulders rolling on Phobos's surface.

The crash that made Stickney was so strong that it could have destroyed Phobos, but the moon's porous, sponge-like structure helped it survive. Inside Stickney's walls, there are patterns caused by material sliding down into the crater. The southwest edge of Stickney has a bluish color, likely due to a thin layer of rock from Stickney and a smaller crater named Limtoc.