Cassini Spacecraft Finds Flooded Canyons on Titan
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| NASA's Cassini spacecraft pinged the surface of Titan with microwaves, finding that some channels are deep, steep-sided canyons filled with liquid hydrocarbons. One such feature is Vid Flumina, the branching network of narrow lines in the upper-left quadrant of the image. Credits: NASA/JPL-Caltech/ASI |
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| Titan's Ligeia Mare. Credit: NASA/JPL-Caltech/ASI |
NASA's Cassini spacecraft has found deep, steep-sided canyons on Saturn's moon Titan that are flooded with liquid hydrocarbons. The finding represents the first direct evidence of the presence of liquid-filled channels on Titan, as well as the first observation of canyons hundreds of meters deep.
A new paper in the journal Geophysical Research Letters describes how scientists analyzed Cassini data from a close pass the spacecraft made over Titan in May 2013. During the flyby, Cassini's radar instrument focused on channels that branch out from the large, northern sea Ligeia Mare.
The Cassini observations reveal that the channels -- in particular, a network of them named Vid Flumina -- are narrow canyons, generally less than a kilometer wide, with slopes steeper than 40 degrees. The canyons also are quite deep -- those measured 240 to 570 meters from top to bottom.
The branching channels appear dark in radar images, much like Titan's methane-rich seas. This suggested to scientists that the channels might also be filled with liquid, but a direct detection had not been made until now. Previously it wasn't clear if the dark material was liquid or merely saturated sediment -- which at Titan's frigid temperatures would be made of ice, not rock.
Cassini's radar is often used as an imager, providing a window to peer through the dense haze that surrounds Titan to reveal the surface below. But during this pass, the radar was used as an altimeter, sending pings of radio waves to the moon's surface to measure the height of features there. The researchers combined the altimetry data with previous radar images of the region to make their discovery.
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| The northern polar area of Titan and Vid Flumina drainage basin. (left) On top of the image, the Ligeia Mare; in the lower right the North Kraken Mare; the two seas are connected each other by a labyrinth of channels. On the left, near the North pole, the Punga Mare. Red arrows indicate the position of the two flumina significant for this work. credit: Geophysical Research Letters. |
Key to understanding the nature of the channels was the way Cassini's radar signal reflected off the bottoms of the features. The radar instrument observed a glint, indicating an extremely smooth surface like that observed from Titan's hydrocarbon seas. The timing of the radar echoes, as they bounced off the canyons' edges and floors, provided a direct measure of their depths.
The presence of such deep cuts in the landscape indicates that whatever process created them was active for a long time or eroded down much faster than other areas on Titan’s surface. The researchers' proposed scenarios include uplift of the terrain and changes in sea level, or perhaps both.
"It's likely that a combination of these forces contributed to the formation of the deep canyons, but at present it's not clear to what degree each was involved. What is clear is that any description of Titan's geological evolution needs to be able to explain how the canyons got there," said Valerio Poggiali of the University of Rome, a Cassini radar team associate and lead author of the study.
Earthly examples of both of these types of canyon-carving processes are found along the Colorado River in Arizona. An example of uplift powering erosion is the Grand Canyon, where the terrain's rising altitude caused the river to cut deeply downward into the landscape over the course of several million years. For canyon formation driven by variations in water level, look to Lake Powell. When the water level in the reservoir drops, it increases the river's rate of erosion.
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| Acquisition scenario and echoes received from Vid Flumina canyons. credit: Geophysical Research Letters. |
"Earth is warm and rocky, with rivers of water, while Titan is cold and icy, with rivers of methane. And yet it's remarkable that we find such similar features on both worlds," said Alex Hayes, a Cassini radar team associate at Cornell University, Ithaca, New York, and a co-author of the study.
While the altimeter data also showed that the liquid in some of the canyons around Ligeia Mare is at sea level -- the same altitude as the liquid in the sea itself -- in others it sits tens of meters higher in elevation. The researchers interpret the latter to be tributaries that drain into the main channels below.
Future work will extend the methods used in this study to all other channels Cassini's radar altimeter has observed on Titan. The researchers expect their continued work to produce a more comprehensive understanding of forces that have shaped the Saturnian moon's landscape.
Credits: NASA/JPL-Caltech/ASI, American Geophysical Union, Wikipedia
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La nave espacial Cassini encuentra cañones inundados en Titán
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| Hazy Orange Orb of Titan. Credit: NASA/JPL-Caltech/Space Science Institute |
La nave espacial de la NASA Cassini ha encontrado profundos y empinados cañones en la luna de Saturno Titán, estos están inundados con hidrocarbonos lÃquidos. Los hallazgos representan la primera evidencia de la presencia de canales rellenos con lÃquido en Titán, además de la primera observación de cañones cientos de metros de profundidad.
Un nuevo artÃculo en la revista Geophysical Research Letters describe como los cientÃficos analizaron la información de la Cassini de un acercamiento realizado en mayo de 2013. Durante el sobrevuelo, el radar de la Cassini se centró sobre lso canales que se abrÃan desde el gran mar del Norte Ligeia Mare.
Las observaciones de Cassini revelaron que los canales --en particular, un entramado de ellos llamado Vid Flumina – son estrechos cañones, por lo general menos de un kilómetro de anchura, con pendientes mayores a los 40 grados. Los cañones son bastantes profundos – los cuales median entre 240 a 570 metros de arriba abajo.
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| Titan's Nile-Like River Valley, the canyons of Vid Flumina. Credits: NASA/JPL-Caltech/ASI |
El radar de la Cassini es a menudo usado como realizador de imágenes, dotándonos de una ventana por donde mirar la densa bruma que envuelve a Titán para mostrarnos la superficie más abajo. Pero durante este pase el radar se usó como un altÃmetro, mandándonos señales de ondas de radio de la superficie de la luna para medir la altura de estos elementos del lugar. Los investigadores combinaron la información de la altimetrÃa con imágenes de radar anteriores de la región para realizar este descubrimiento.
La clave para entender la naturaleza de los canales fue en la manera en que Cassini reflejo la imagen del fondo de estos elementos. El instrumento del radar observo un destello, indicando una superficie extremadamente lisa como las observadas en los mares de hidrocarbonos de Titán. La coordinación del echo del radar, a la vez que este rebotaba desde los bordes de los cañones y su lecho, proporcionaron una medida directa de sus profundidades.
La presencia de dichos cortes profundos en el paisaje indica que procesos climatológicos fueron los causantes de estos y que estuvieron activos por un largo periodo o que hubo una erosión mucho más rápida que en otras áreas de la superficie de Titán. Los investigadores han propuesto modelos en que se incluye el alzamiento de la superficie del terreno y cambios en el nivel del mar, o quizás una combinación de ambas.
“Es posible que unas combinaciones de estas fuerzas hayan contribuido a la formación de estos profundos cañones, pero de momento no está claro en qué grado nivel están relacionas cada una de estas fuerzas. Lo que está claro es que cualquiera descripción de la evolución de la geologÃa de Titán requiere la explicación de cómo esos cañones están ahÃ,” dijo Valerio Poggiali de la Universidad de Roma, uno de los técnicos de radar de la Cassini y lÃder de la investigación.
Earthly examples of both of these types of canyon-carving processes are found along the Colorado River in Arizona. An example of uplift powering erosion is the Grand Canyon, where the terrain's rising altitude caused the river to cut deeply downward into the landscape over the course of several million years. For canyon formation driven by variations in water level, look to Lake Powell. When the water level in the reservoir drops, it increases the river's rate of erosion.
“La Tierra es cálida y rocosa, con rÃos, mientras que Titán es frio y helado, con rÃos de metano. Y aun asà es increÃble que encontremos elementos tan similares en ambos mundos,” dijo Alex Hayes, del equipo de radar de la Cassini en la Universidad de Cornell en Ithaca, New York, y coautor de la investigación.
Mientras tanto el altÃmetro también mostraba información de que el lÃquido de los cañones alrededor de la región Ligeia Mare está a nivel del mar – la misma altura del lÃquido en el propio mar – mientras que en otros sitios se asentaba a decena de metros por encima en elevación. Los investigadores han interpretado este último dato como que estos fueran tributarios que drenan en los canales principales mas abajo.
Un futuro trabajo ampliara los métodos usado en este estudio a todos los otros canales que el altÃmetro de la Cassini ha observado. Los investigadores esperan que la continuación de este trabajo produzca una mayor comprensión y entendimiento de las fuerzas que han formado el paisaje de la luna de Saturno.
Credits: NASA/JPL-Caltech/ASI, American Geophysical Union, Wikipedia
