Ontario Lacus
Encyclopedia
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
composed of methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, ethane
Ethane
Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane that is an aliphatic hydrocarbon. At standard temperature and pressure, ethane is a colorless, odorless gas....
and propane
Propane
Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...
near the south pole of 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 Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
. Its character as a hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
lake was confirmed by observations from the Cassini spacecraft, published in the 31 July 2008 edition of Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
. Ontario Lacūs has a surface area of about 15000 square kilometres (5,791.5 sq mi), slightly smaller than its terrestrial namesake, Lake Ontario
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north and southwest by the Canadian province of Ontario, and on the south by the American state of New York. Ontario, Canada's most populous province, was named for the lake. In the Wyandot language, ontarío means...
in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
On January 12, 2010, Cassini took a more detailed radar-image
Imaging radar
Traditional radar sends directional pulses of electromagnetic energy and detects the presence, position and motion of an object by analyzing the portion of the energy reflected from the object back to the radar station. Imaging radar attempts to form a picture of the object as well, by mapping...
of Ontario Lacūs showing numerous remarkable features. The northern shoreline features low hill
Hill
A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit A hill is a landform that extends above the surrounding terrain. Hills...
s, probably about 1 kilometer (3,000 feet) in altitude, and flooded river valleys. A smooth, wave-sculpted shoreline, like that seen on the southeastern side of Lake Michigan
Lake Michigan
Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...
, can be seen at the northeastern part of the lake. Smooth lines parallel to the current shoreline could be formed by low wave
Wave
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...
s over time, which were likely driven by winds sweeping in from the west or southwest. The southeast shore features a round-headed bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
intruding into the shore.
The middle part of the western shoreline shows the first well-developed river delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
observed on Titan, showing that liquid hydrocarbons flowing down from a higher plain have switched channels
Stream channel
Stream channel is the physical confine of a stream consisting of a bed and stream banks.Stream channels exist in a variety of geometries. The stream channel development is controlled by both water and sediment movement. There is a difference between low gradient streams and high gradient streams...
on their way into the lake, forming at least two lobes. Examples of this kind of channel switching and wave-modified deltas can be found on Earth at the southern end of Lake Albert between Uganda
Uganda
Uganda , officially the Republic of Uganda, is a landlocked country in East Africa. Uganda is also known as the "Pearl of Africa". It is bordered on the east by Kenya, on the north by South Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by...
and the Democratic Republic of Congo in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and the remains of an ancient lake known as Megachad in the African country Chad
Chad
Chad , officially known as the Republic of Chad, is a landlocked country in Central Africa. It is bordered by Libya to the north, Sudan to the east, the Central African Republic to the south, Cameroon and Nigeria to the southwest, and Niger to the west...
.
By terrestrial standards, the lake appears to be extremely shallow. Radar measurements made in July 2009 and January 2010 indicate an average depth of 0.4 – 3.2 m, and a maximum depth of 2.9 – 7.4 m. This gives the lake an estimated volume of 7 to 50 km3, less than one thirtieth the volume of Earth's Lake Ontario. Any waves present on the lake are also far smaller than those that would be present on a sizable body of liquid water on Earth; their estimated maximum height is less than 1 mm. This could either indicate a complete lack of wind, or a viscous composition of the hydrocarbon fluid.