Stickney (crater)
The crater Stickney dominates the surface of Phobos, the inner satellite orbiting Mars. It spans 9 kilometers in diameter and occupies a substantial portion of that small moon's landscape. This massive scar bears the name of Chloe Angeline Hall Stickney, a mathematician who supported her husband Asaph Hall. He credited her assistance as critical to his discovery of the moon itself. The International Astronomical Union officially assigned this name in 1973. Committee chair Carl Sagan led the nomenclature group that made the decision. They based their choice on images captured by the Mariner 9 spacecraft.
Scientists propose two distinct ages for the impact depending on when Phobos began its journey around Mars. If the moon has orbited for 4.3 billion years, then Stickney formed 4.2 billion years ago. Alternatively, if Phobos only started orbiting 3.5 billion years ago, the collision happened 2.6 billion years ago. The impact ejected large amounts of debris into space. Some material escaped Phobos gravity entirely and entered orbit around Mars. This debris remained in Martian orbit for no more than 1000 years before crashing back down. Much of it struck Phobos again to create secondary craters. Most craters smaller than 600 meters across resulted from these secondary impacts.
Debris from the original collision traveled briefly through space before returning to the surface. A significant portion of this ejecta crashed back onto Phobos itself. These returning fragments created numerous smaller craters scattered across the moon. The majority of features under 600 meters in diameter stem from these secondary events. Scientists observe that the distribution of these small craters maps the path of the initial explosion. The process demonstrates how a single massive event can generate thousands of smaller scars over time. This pattern helps researchers understand the history of bombardment on the inner satellite.
Grooves radiate outward from Stickney like lines drawn by a compass. One theory suggests these marks formed from stress caused by the impact. If true, the blow nearly destroyed Phobos during its formation. Other explanations exist regarding their origin. Some researchers believe material ejected from impacts on Mars created the patterns. Others argue tidal forces exerted by the Red Planet shaped the grooves. A third group proposes boulders rolling along the surface after the collision made the lines. The debate continues as scientists examine the physical evidence left behind.
A study published in 2016 by Syal and colleagues examined why Phobos survived such a violent collision. They found high porosity within the moon allowed it to absorb the energy without shattering. Without this porous structure, the object would have been destroyed. Models suggest the area beneath Stickney might be denser than the rest of the moon. However, theories about the interior vary significantly among experts. The research highlights how internal composition determines survival against catastrophic events.
Landslides created lineated textures inside the crater walls where materials fell downward. These slopes show clear signs of past movement and collapse. Spectral analysis reveals a unique blue layer on the southwestern edge of the feature. This coloration likely represents a relatively thin layer of rock exposed by the impact. Scientists theorize the hue resulted from a mix of material originating from Stickney itself. Some of the coloring also came from the smaller interior crater named Limtoc. The combination of these sources produced the distinct visual signature seen today.
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Common questions
What is the diameter of Stickney crater on Phobos?
Stickney crater spans 9 kilometers in diameter. It occupies a substantial portion of the small moon's landscape.
Who was Chloe Angeline Hall Stickney and why does the crater bear her name?
Chloe Angeline Hall Stickney was a mathematician who supported her husband Asaph Hall. He credited her assistance as critical to his discovery of the moon itself, leading the International Astronomical Union to officially assign this name in 1973.
When did Stickney crater form on Phobos according to scientific theories?
Scientists propose two distinct ages for the impact depending on when Phobos began its journey around Mars. If the moon has orbited for 4.3 billion years, then Stickney formed 4.2 billion years ago, but if it started orbiting 3.5 billion years ago, the collision happened 2.6 billion years ago.
How many craters smaller than 600 meters across resulted from secondary impacts after the Stickney collision?
Most craters smaller than 600 meters across resulted from these secondary impacts. Debris ejected from the original collision traveled briefly through space before returning to the surface to create numerous smaller craters scattered across the moon.
What caused the grooves that radiate outward from Stickney like lines drawn by a compass?
One theory suggests these marks formed from stress caused by the impact. Other explanations exist regarding their origin including material ejected from impacts on Mars creating patterns or tidal forces exerted by the Red Planet shaping the grooves.
Why did Phobos survive the violent collision that created Stickney crater in 2016 research?
A study published in 2016 by Syal and colleagues found high porosity within the moon allowed it to absorb the energy without shattering. Without this porous structure, the object would have been destroyed.