Odysseus is the largest

crater Crater may refer to: Landforms *Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet *Explosion crater, a hole formed in the ground produced by an explosion near or below the surfac ...

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

Tethys. It is 445 km across, more than 2/5 of the moon's diameter, and is one of the largest craters in the Solar System. It is situated in the western part of the leading hemisphere of the moon—the latitude and longitude of its center are 32.8°N and 128.9°W, respectively. It is named after the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

hero

Odysseus Odysseus ( ; grc-gre, Ὀδυσσεύς, Ὀδυσεύς, OdysseúsOdyseús, ), also known by the Latin variant Ulysses ( , ; lat, UlyssesUlixes), is a legendary Greek king of Ithaca and the hero of Homer's epic poem the ''Odyssey''. Odysse ...

from Homer's the ''

Iliad The ''Iliad'' (; grc, Ἰλιάς, Iliás, ; "a poem about Ilium") is one of two major ancient Greek epic poems attributed to Homer. It is one of the oldest extant works of literature still widely read by modern audiences. As with the ''Odysse ...

'' and the ''

Odyssey The ''Odyssey'' (; grc, Ὀδύσσεια, Odýsseia, ) is one of two major Ancient Greek literature, ancient Greek Epic poetry, epic poems attributed to Homer. It is one of the oldest extant works of literature still widely read by moder ...

''. Odysseus was discovered by the ''

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...

'' spacecraft on 1 September 1981 during its flyby of Saturn.

Geology

Tethys high resolution color map and topography PIA13701

The Odysseus crater is now quite flat for its size of approximately 450 km or more precisely, its floor conforms to Tethys' spherical shape. This is most likely due to the viscous relaxation of the Tethyan icy crust over geologic time. The floor lies approximately 3 km below the mean radius, while its exterior rim is about 5 km above the mean radius—the relief of 6–9 km is not very high for such a large crater. Inside the crater the rim is composed of arcuate scarps and extends for about 100 km until the floor is reached. There are several graben radiating away from Odysseus, which are 10–20 km wide and hundreds of kilometers long. They are likely to be cracks in the crust created by the impact. The most prominent among them is called ''Ogygia Chasma''. The crater must have originally been deep, with a high mountainous rim and towering central peak. Over time the crater floor has relaxed to the spherical shape of the Tethyan surface, and the crater's rim and central peak have collapsed (similar relaxation is apparent on Jupiter's moons

Callisto Callisto most commonly refers to: *Callisto (mythology), a nymph *Callisto (moon), a moon of Jupiter Callisto may also refer to: Art and entertainment *''Callisto series'', a sequence of novels by Lin Carter *''Callisto'', a novel by Torsten Kro ...

and Ganymede). This indicates that at the time of the Odysseus impact, Tethys must have been sufficiently warm and malleable to allow the topography to collapse; its interior may have even been

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

. If Tethys had been colder and more brittle at the time of impact, the moon might have been shattered, and even if it survived the impact, the topography of the crater would have retained its shape, similarly to the crater Herschel on Mimas. The central complex of Odysseus (''Scheria Montes'') features a central pit-like depression, which is 2–4 km deep. It is surrounded by massifs elevated by 2–3 km above the crater floor, which itself is about 3 km below the average radius.

Relation to Ithaca Chasma

The immense trench called

Ithaca Chasma Ithaca Chasma is a valley (graben) of Saturn's moon Tethys, named after the island of Ithaca, in Greece. It is up to wide, deep and long, running approximately three-quarters of the way around Tethys' circumference, making it one of the long ...

, which approximately follows a great circle with a pole near Odysseus' center, had been hypothesized to have formed as a result of the Odysseus impact. However, a study based on high resolution Cassini images indicated that this is unlikely—the crater counts inside Odysseus appear to be lower than in Ithaca Chasma, indicating that the latter is older than the former.

References

External links

* *

Astronomy Picture of the Day Astronomy Picture of the Day (APOD) is a website provided by NASA and Michigan Technological University (MTU). According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written ...

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9 September 2007
* {{Tethys Impact craters on Saturn's moons Surface features of Tethys (moon)