From: Planetary Science Institute
Posted: Tuesday, December 4, 2012
Dec. 4, 2012, Tucson, Ariz. -- An international research team led by the Planetary Science Institute has found evidence that indicates that approximately 2 billion years ago enormous volumes of catastrophic floods discharges may have been captured by extensive systems of caverns on Mars, said PSI Research Scientist, J. Alexis Palmero Rodriguez.
Image: Close-up views of study region; context and locations shown in Figure 1. All scale bars correspond to 5 km. (a) Site 1. THEMIS VIS images V11629004 and V12852005 centered at 126°47' E., 20°35' N. (b) Zone of knickpoint (black arrow) retreat shown in panel a. CTX image P13_006196_1998 centered at 126°43' E., 20°33' N. (c) Elevation profiles located in panel b. (d) Site 2. Composite of THEMIS VIS images V02617006, V12877003 and V01868003 centered at 125°36' E., 21°34' N. (e) Zone of knickpoint retreat (black arrow) shown in panel d. CTX image P17_007765_2015 centered at 125°40' E., 21°44' N. (f ) Part of Hephaestus Fossae. CTX image B18_016560_2033 centered at 122°70' E., 22°00' N. (g) Zone north of site 2 where systems of linear depressions interconnect clusters of features interpreted as mud volcanoes. Part of CTX image B18_016705_2048 centered at 125°18' E., 25°00' N. (h) Zone where Hebrus Valles dissects a plain modified by mud volcanism. Part of CTX image P02_001805_1996 centered at 126°47'E., 19°28' N.
Rodriguez and the research team came to this conclusion after studying the terminal regions of the Hebrus Valles, an outflow channel that extends approximately 250 kilometers downstream from two zones of surface collapse.
The Martian outflow channels comprise some of the largest known channels in the solar system. Although it has been proposed their discharge history may have once led to the formation of oceans, the ultimate fate and nature of the fluid discharges has remained a mystery for more than 40 years, and their excavation has been attributed to surface erosion by glaciers, debris flows, catastrophic floodwaters, and perhaps even lava flows, Rodriguez said.
The PSI-led team's work documents the geomorphology of Hebrus Valles, a Martian terrain that is unique in that it preserves pristine landforms located at the terminal reaches of a Martian outflow channel. These generally appear highly resurfaced, or buried, at other locations in the planet. Rodriguez and his co-authors propose in an article titled "Infiltration of Martian overflow channel floodwaters into lowland cavernous systems" published in Geophysical Research Letters that large volumes of catastrophic floodwaters, which participated in the excavation of Hebrus Valles, may have encountered their ultimate fate in vast cavernous systems.
They hypothesize that evacuated subsurface space during mud volcanism was an important process in cavern development. Mud volcanism can expel vast volumes of subsurface volatiles and sediments to the surface. But because evacuation of subsurface materials generally occurs within unconsolidated sediments resulting caverns are transient and mechanically highly unstable.
However, the investigated Martian caverns appear to have developed within permafrost, which at -65 degrees Celsius (-85 degree Fahrenheit) - a typical mean annual surface temperature for the investigated latitudes - has a mechanical strength similar to that of limestone. Limestone rocks host most of the terrestrial cavern systems.
Possible cavern have been recently identified on Mars and their existence has caught much scientific and public attention because of their potential as exobiological habitats. However, their age and dimensions remain uncertain. The discovery of vast caverns that existed in ancient periods of Mars shows that these habitats may have in fact existed during billions of years of the planet's history, Rodriguez said.
PSI Senior Scientist Mary Bourke and Research Scientist Daniel C. Berman are co-authors on the paper.
This research was funded by a grant to PSI from the NASA Mars Data Analysis Program.
J. Alexis Palmero Rodriguez
Mark V. Sykes
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Celebrating its 40th anniversary, the Planetary Science Institute is a private, nonprofit 501(c)(3) corporation dedicated to solar system exploration. It is headquartered in Tucson, Arizona, where it was founded in 1972.
PSI scientists are involved in numerous NASA and international missions, the study of Mars and other planets, the Moon, asteroids, comets, interplanetary dust, impact physics, the origin of the solar system, extra-solar planet formation, dynamics, the rise of life, and other areas of research. They conduct fieldwork in North America, Australia and Africa. They also are actively involved in science education and public outreach through school programs, children's books, popular science books and art.
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