Odysseus (crater)
Encyclopedia
Odysseus is the largest crater
on Saturn
's moon
Tethys
. It is 445 km across, more than 2/5 of the moon's diameter, and is one of the larger craters in the Solar System. It is situated in the western part of 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
hero Odysseus
.
spacecraft on 1 September 1981 during its flyby of Saturn. It was named after the Greek
hero Odysseus
from Homer's Odyssey
and Iliad
.
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 Tethys's surface, and the crater's rim and central peak have collapsed (similar relaxation is apparent on Jupiter's moons Callisto
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
. 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, similar 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 6–9 km above the crater floor, which itself is about 3 km below the average radius.
, which approximately follows a great circle with a pole near Odyssues' center, had been hypothesized to have formed as a result of the Odysseus impact. However, a research 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.
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
on Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
's moon
Natural satellite
A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....
Tethys
Tethys (moon)
Tethys or Saturn III is a mid-sized moon of Saturn about across. It was discovered by G. D. Cassini in 1684 and is named after titan Tethys of Greek mythology. Tethys is pronounced |Odysseus]] is about 400 km in diameter, while the largest graben—Ithaca Chasma is about 100 km wide and...
. It is 445 km across, more than 2/5 of the moon's diameter, and is one of the larger craters in the Solar System. It is situated in the western part of 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 mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
hero Odysseus
Odysseus
Odysseus or Ulysses was a legendary Greek king of Ithaca and the hero of Homer's epic poem the Odyssey. Odysseus also plays a key role in Homer's Iliad and other works in the Epic Cycle....
.
Discovery
Odysseus was discovered by Voyager 2Voyager 2
The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...
spacecraft on 1 September 1981 during its flyby of Saturn. It was named after the Greek
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
hero Odysseus
Odysseus
Odysseus or Ulysses was a legendary Greek king of Ithaca and the hero of Homer's epic poem the Odyssey. Odysseus also plays a key role in Homer's Iliad and other works in the Epic Cycle....
from Homer's Odyssey
Odyssey
The Odyssey is one of two major ancient Greek epic poems attributed to Homer. It is, in part, a sequel to the Iliad, the other work ascribed to Homer. The poem is fundamental to the modern Western canon, and is the second—the Iliad being the first—extant work of Western literature...
and Iliad
Iliad
The Iliad is an epic poem in dactylic hexameters, traditionally attributed to Homer. Set during the Trojan War, the ten-year siege of the city of Troy by a coalition of Greek states, it tells of the battles and events during the weeks of a quarrel between King Agamemnon and the warrior Achilles...
.
Geology
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 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 Tethys's surface, and the crater's rim and central peak have collapsed (similar relaxation is apparent on Jupiter's moons Callisto
Callisto (moon)
Callisto named after the Greek mythological figure of Callisto) is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede. Callisto has about 99% the diameter of the...
and Ganymede
Ganymede (moon)
Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...
). 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
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
. 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, similar to the crater Herschel on Mimas
Mimas (moon)
Mimas is a moon of Saturn which was discovered in 1789 by William Herschel. It is named after Mimas, a son of Gaia in Greek mythology, and is also designated Saturn I....
.
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 6–9 km above the crater floor, which itself is about 3 km below the average radius.
Relation to Ithaca Chasma
The immense trench called Ithaca ChasmaIthaca Chasma
Ithaca Chasma is a valley on Saturn's moon Tethys, named after the island of Ithaca, in Greece. It is on average 100 km wide, 3 to 5 km deep and 2,000 km long, running approximately three-quarters of the way around Tethys' circumference, making it one of the longer valleys in the...
, which approximately follows a great circle with a pole near Odyssues' center, had been hypothesized to have formed as a result of the Odysseus impact. However, a research 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.
Gallery
External links
- Astronomy Picture of the DayAstronomy Picture of the DayAstronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...
for 9th September 2007