Hargraves (crater)
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Nili Fossae
Greater Isidis region
 Viking Orbiter 1 image with Hargraves as the largest crater at center-right | |
| Planet | Mars |
|---|---|
| Region | Syrtis Major quadrangle Nili Fossae Greater Isidis region |
| Coordinates | 20°44′N 75°44′E / 20.74°N 75.74°E |
| Quadrangle | Syrtis Major |
| Diameter | 60.28 km[1] 69 km[2] |
Hargraves is a Hesperian-age complex double-layered ejecta impact crater on Mars. It was emplaced near the crustal dichotomy in the vicinity of the Nili Fossae, the Syrtis Major volcanic plains, and the Isidis impact basin, and is situated within the Syrtis Major quadrangle. Hargraves has been the target of focused study because its ejecta apron is particularly well-preserved for a Martian crater of its size. It has been analogized to similar double-layered ejecta blankets on Earth, including that of the Ries impact structure, which was where the conceptual model for how such craters formed was first advanced.
The presence of Hargraves ejecta in a trough of the Nili Fossae to its west, contributed to a consideration of the Nili Fossae as a possible candidate landing site for NASA's Perseverance rover. The presence of certain minerals (phyllosilicates, serpentine, and magnesite) detected remotely in Hargraves ejecta imply aqueous alteration either at the time of the Hargraves impact or by virtue of a hydrothermal system active after impact.
Hargraves lies near the crustal dichotomy of Mars in the vicinity of the Syrtis Major volcanic province. It is located between the two largest fossae (graben) of the Nili Fossae,[2] which are troughs to the northeast of Isidis Planitia that are concentric to the impact site that likely excavated it. The crater lies over 100 km to the northwest of Jezero Crater, the landing site of NASA's Perseverance rover, which arrived on Mars in February 2021.[3]
During the landing site selection process for Perseverance, a site in the Nili Fossae graben due west of Hargraves Crater was evaluated as a finalist in part because of the likelihood that blocks exhumed from depth by Hargraves were thought to be present in the vicinity of the landing ellipse. Clay-bearing materials, carbonate minerals (magnesite), and serpentine were also associated with the Hargraves ejecta apron, implying either syn- or post-impact non-acidic aqueous alteration, the latter case possibly involving hydrothermal activity.[4][5] Early assessments of regions of interest scrutinized Hargraves Crater itself as a possibly valuable science target in the Nili Fossae region.[6] Final downselection of the rover landing sites eventually favored nearby Jezero crater over the Nili Fossae candidate.[4]
Hargraves Crater is named after the South African and American geoscientist Robert B. Hargraves, by the IAU in 2006, following his death in 2003.[1] Hargraves studied impact structures on Earth and lunar samples returned by the Apollo program. He was also a participant in the Viking program to Mars.[7]