{{Short description|Rivers of liquid methane and ethane on Saturn's moon Titan}} {{Use dmy dates|date=November 2024}} {{Infobox river | image_caption = [[Synthetic aperture radar]] image from [[Cassini–Huygens|''Cassini'']] of Vid Flumina flowing into [[Ligeia Mare]] on [[Titan (moon)|Titan]] | name_etymology = From the [[Vimur River|Við or Vimur River]] from Norse Mythology | subdivision_type1 = Moon | subdivision_name1 = [[Titan (moon)|Titan]] | length = >400 km<ref name="AGUcanyons"/> | mouth = [[Ligeia Mare]] | discharge1_avg = 40 m<sup>3</sup>/s (2013, predicted)<ref name="Tokano2019">{{cite journal |last1=Tokano |first1=Tetsuya |last2=Lorenz |first2=Ralph D. |title=Modeling of Seasonal Lake Level Fluctuations of Titan's Seas/Lakes |date=February 2019 |journal=Journal of Geophysical Research: Planets |volume=124 |issue=2 |pages=617–635 |doi=10.1029/2018JE005898 |doi-access=free |bibcode=2019JGRE..124..617T }}</ref>{{rp|629}} | custom_label = Discoverer | custom_data = ''[[Cassini–Huygens|Cassini]]'' | map = {{Superimpose | base = PIA17655 crop Titan north polar seas and lakes.jpg | base_width = 250px | base_alt = Located south of [[Ligeia Mare]] on Saturn's moon Titan. | base_caption = Location of the mouth of Vid Flumina, near Titan's north pole | float = Red pog.svg | float_width = 10px | x = 169 | y = 160 }} }} [[File:PIA16197 Titan river.jpg|thumb|160px |[[Synthetic aperture radar]] image mosaic of Titan's north polar region]]
'''Vid Flumina''' is a [[Drainage system (geomorphology)|river system]] (termed ''[[Flumen (planetary geology)|Flumen]]'') of liquid [[methane]] and [[ethane]] on [[Saturn]]'s moon [[Titan (moon)|Titan]]. It is more than {{convert|400|km|mi|0|abbr=on}} long and flows into Titan's second largest hydrocarbon sea, [[Ligeia Mare]].<ref name="AGUcanyons"/> The surface of Titan is mostly water ice, so Vid Flumina is a river of methane and ethane flowing across and cutting canyons into ice as though it were bedrock. NASA scientists think that it likely has rapids, whirlpools and falls, just like rivers on Earth.
==Discovery and naming==
=== Earlier findings === In 2004, [[NASA]]'s probe, [[Cassini–Huygens|''Cassini'']] arrived at Saturn to study it and its moons. The scientists at NASA were expecting to find some evidence for liquid methane because of Titan's surface temperature and its methane-rich atmosphere. However, ''Cassini''{{'s}} early findings that were focused on Titan's equator revealed no traces of seas or rivers.<ref name="discovermagazine.com">{{Cite web |title=Cassini Finds a New Nile River on Titan |url=https://www.discovermagazine.com/the-sciences/cassini-finds-a-new-nile-river-on-titan |access-date=2022-10-25 |website=Discover Magazine |language=en}}</ref>
The early disappointment changed as the ''Cassini''{{'s}} orbit shifted and allowed the researchers at NASA to bounce radar off other regions of the moon. The radar signals were then routinely reflected off angled, rough features such as sand dunes and rocks and cliffs, but when the radar reached the polar regions of Titan, the regular signals ceased. These non-reflecting dark spots were actually reminiscent of the lakes, rivers and tributaries on Earth.<ref name="discovermagazine.com"/>
=== Discovery === In December 2012, [[Jani Radebaugh]], a scientist on ''Cassini''{{'s}} team along with an international team of colleagues, announced that they had discovered a liquid methane river of over 200 miles resembling the [[Nile]] from an image taken on 26 September 2012.<ref name="discovermagazine.com"/>
=== Naming === The river is named after a mythological river in [[Norse mythology]] that was part of the [[Élivágar]] system of extremely cold and poisonous rivers in [[Ginnungagap]]. The name was approved by the [[International Astronomical Union]] on 13 February 2013.<ref name="USGS">{{Cite web |title=Gazetteer of Planetary Nomenclature - Vid Flumina |url=https://planetarynames.wr.usgs.gov/Feature/15088 |access-date=2024-11-27 |website=wr.usgs.gov}}</ref>
==Geology== The river flows along a relatively straight course, suggesting that it follows one or more [[fault line]]s, similar to other large nearby rivers.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20121212.html|title=NASA - Cassini Spots Mini Nile River on Saturn Moon|publisher=|access-date=26 April 2016|archive-date=5 January 2022|archive-url=https://web.archive.org/web/20220105051050/http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20121212.html|url-status=dead}}</ref><ref>{{cite web|url=https://beyondearthlyskies.blogspot.com/2013/05/a-river-on-titan.html|title=Beyond Earthly Skies: A River on Titan|first=Koh Xuan|last=Yang|date=24 May 2013|publisher=}}</ref> The river slices through a rough and slanted terrain, which suggests operation of processes similar to tectonic movements on Earth.
Radar studies show that Vid Flumina and its tributaries flow through canyons about one km wide and 0.57 km deep, with slopes of about 40°. Flowing methane was detected in the channels. The elevation of the main channel was found to be within 1 m of that of [[Ligeia Mare]], while tributary channels have higher elevations. The canyons are thought to have formed by erosion stimulated either by uplift of the area or a decline in the level of Ligeia Mare.<ref name = "AGU-JPL2016">{{cite web | url = http://news.agu.org/press-release/methane-filled-canyons-line-titans-surface-study-finds/ | title = Methane-filled canyons line Titan's surface, study finds | date = 2016-08-10 | website = news.AGU.org | publisher = [[American Geophysical Union]] and [[Jet Propulsion Laboratory]] | access-date = 2016-08-11}}</ref><ref name="Poggiali2016">{{cite journal|last1=Poggiali|first1=V.|last2=Mastrogiuseppe|first2=M.|last3=Hayes|first3=A. G.|last4=Seu|first4=R.|last5=Birch|first5=S. P. D.|last6=Lorenz|first6=R.|last7=Grima|first7=C.|last8=Hofgartner|first8=J. D.|title=Liquid-filled canyons on Titan|journal=Geophysical Research Letters|date=2016-08-09|volume=43 |issue=15 |pages=7887–7894 |doi=10.1002/2016GL069679|bibcode=2016GeoRL..43.7887P|url=https://iris.uniroma1.it/bitstream/11573/932488/1/Poggiali_Liquid-filled_2016.pdf|hdl=11573/932488|s2cid=132445293 |hdl-access=free}}</ref>
==See also== *[[Elivagar Flumina]] *[[Saraswati Flumen]]
== References == <references>
<ref name="AGUcanyons">{{Cite web |title=Methane-filled canyons line Titan's surface, study finds |url=https://news.agu.org/press-release/methane-filled-canyons-line-titans-surface-study-finds/ |access-date=1 April 2024 |website=AGU |language=en}}</ref>
</references>
{{Titan}} [[Category:Rivers]] [[Category:Surface features of Titan (moon)]]