Overview

Stickney is the dominant impact basin on Phobos, the larger and closer of Mars's two small moons. The crater measures roughly 9 km across, a size that occupies a substantial portion of Phobos's surface and gives the moon its distinctive, pockmarked appearance. Its approximate center is near 1°N, 49°W; precise coordinates are often cited in mission data and maps for navigation and study (coordinates).

Physical characteristics

Stickney's rim, steep walls and interior show a variety of features typical of large impacts on small, low-gravity bodies. The basin's floor contains boulder fields, regions of fine regolith, and chains of grooves and troughs that extend across nearby terrain. Because Stickney is so large relative to Phobos, the impact disturbed much of the moon's crust and regolith, producing patterns of fractures and ejecta that are visible in spacecraft imagery.

Formation and geological effects

The crater formed when a relatively large impactor struck Phobos at high speed, excavating material and sending debris across the surface. Scientists debate the precise mechanics that produced the long, linear grooves on Phobos; many analyses propose that some grooves radiate from or are associated with the Stickney impact, either as chains of secondary craters from ejecta or as stress fractures produced by the collision. The event likely altered Phobos's structural integrity and redistributed surface material on a global scale.

Scientific importance and exploration

Stickney is a key target for understanding impact processes on very small bodies and for planning missions to Phobos. Its size relative to the moon makes it instructive for models of crater formation in low gravity and for studies of regolith transport, slope processes and space weathering. Observations from orbiters and proposed lander missions focus on Stickney to sample diverse materials and to assess hazards and engineering constraints for surface operations near steep rims and boulder-strewn interiors. For context on Phobos and missions, see resources about the moon (Phobos), its role as a natural satellite of Mars, and listings of prominent surface features (largest crater).

Naming and historical notes

The crater is named after Chloe Angeline Stickney Hall, the wife of Asaph Hall, who discovered Phobos and Deimos in 1877. The name honors her connection to the discovery and appears in astronomical nomenclature used by planetary scientists and mapping authorities. As one of the most conspicuous landmarks on Phobos, Stickney has been photographed and analyzed by multiple Mars missions that have returned imagery and measurements used in scientific papers and mission planning.

Notable facts

  • With a diameter comparable to the moon's own dimensions, Stickney is unusually large relative to its host body.
  • Groove systems near Stickney are among the most studied features on Phobos because they may record the moon's mechanical response to a major impact.
  • Stickney's rim and ejecta fields make it both a scientific opportunity and a potential hazard for future landed missions seeking samples or geological context.