Stickney Crater
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Stickney is the largest
crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...
on Phobos, which is a satellite of Mars. It is in diameter, taking up a substantial proportion of the moon's surface.


Naming

The crater is named after mathematician Chloe Angeline Stickney Hall, the wife of Phobos's discoverer
Asaph Hall Asaph Hall III (October 15, 1829 – November 22, 1907) was an American astronomer who is best known for having discovered the two moons of Mars, Deimos and Phobos, in 1877. He determined the orbits of satellites of other planets and of doubl ...
, whose support was credited by her husband as critical for his discovery of the moon. The crater was named in 1973, based on ''
Mariner 9 Mariner 9 (Mariner Mars '71 / Mariner-I) was a robotic spacecraft that contributed greatly to the exploration of Mars and was part of the NASA Mariner program. Mariner 9 was launched toward Mars on May 30, 1971, from Spaceport Florida Launch Comp ...
'' images, by an
IAU The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
nomenclature committee chaired by
Carl Sagan Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist and science communicator. His best known scientific contribution is his research on the possibility of extraterrestrial life, including e ...
..


Formation

There are two models for the age of Stickney, based on the differing possible dates at which Phobos began to orbit around Mars. If Phobos has been orbiting for 4.3 Ga (billion years) then Stickney formed 4.2 Ga ago, but if Phobos has only been orbiting for 3.5 Ga then it formed 2.6 Ga ago. The impact created a large amount of
ejecta Ejecta (; ) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic rock, pyroclastic materials (tephra) that came out of a explosive eruption, volcanic explosion and magma eruption v ...
which escaped Phobos's gravity and entered into orbit around Mars for a period not exceeding 1000 years (some crashed back onto Phobos, and creating secondary impact craters). The majority of craters on Phobos that are smaller than 600 meters in diameter were caused by these secondary impacts.


Physical features

Grooves and
crater chain A crater chain is a line of Impact crater, craters along the surface of an astronomical body. The descriptor term for crater chains is catena , plural catenae (Latin for "chain"), as specified by the International Astronomical Union's rules on ...
s appear to radiate from Stickney. One theory suggests that they were formed as a result of stresses from the impact that created the crater; if true, this suggests that the impact nearly destroyed Phobos itself. There are however numerous other theories as to how they were made, such as that they were formed by material ejected from impacts on Mars, that they were created by
tidal forces The tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field, causing bodies to be pulled unevenly and as a result are being stretched towards the attraction. It is the d ...
exerted by Mars, or even that they were created by boulders rolling along Phobos's surface following the Stickney impact. Regardless of the causes of these grooves, the impact of the object which created Stickney was large enough to have potentially destroyed Phobos; a 2016 study by Syal et al. found that the high
porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
of the moon was critical in preventing it from being destroyed during the collision. It is possible that the area underneath Stickney is much denser and less porous than the rest of Phobos, though models of the moon's interior vary on this. Stickney has a noticeable lineated texture on its interior walls, caused by landslides from materials falling into the crater. There is a noticeable blue spectral coloration on the south-western edge of the crater, which is theorized to be a relatively thin layer of rock. Said coloration was likely caused by a combination of material from Stickney itself and from the smaller, interior crater Limtoc.


See also

*
Moons of Mars The two natural satellite, moons of Mars (planet), Mars are Phobos (moon), Phobos and Deimos (moon), Deimos. They are irregular in shape. Both were discovered by American astronomer Asaph Hall in August 1877 and are named after the Greek mytholo ...
*
Deimos (moon) Deimos (; astronomical naming conventions#Natural satellites, systematic designation: Mars II) is the smaller and outer of the two moons of Mars, natural satellites of Mars, the other being Phobos (moon), Phobos. Deimos has a mean radius of an ...


References


External links


Flight around Phobos
(animated movie)
Stickney in High Resolution

Stickney at APOD
2018 May 5
Creation of Stickney Crater on Phobos (VIDEO)
simulation which shows how Stickney crater was created, and how it affected Phobos, The
Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...
{{DEFAULTSORT:Stickney (Crater) Impact craters on Mars's moons Phobos (moon)