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December 05, 2012

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Did huge caverns swallow up the Martian water?

Dec. 5, 2012
Courtesy of the Planetary Science Institute
and World Science staff

Im­mense cav­ern net­works may have swal­lowed up much of the wa­ter that once coursed over the Red Plan­et, sci­en­tists say.

Re­search­ers stud­ied the He­brus Valles, a chan­nel in the sur­face of Mars pre­sumed to have been carved out by wa­ter or oth­er flu­id. In par­tic­u­lar they ex­am­ined the ter­mi­nal re­gions, where the chan­nel forma­t­ions seem to pe­ter out. A ques­tion was just where the liq­uid might have gone af­ter get­ting there.

An out­flow chan­nel shown in the up­per pan­el ter­mi­nates in the re­gion marked off as "B," and en­larged in the low­er pan­el. Sci­en­tists say that's where a net­work of pits and troughs may point to un­der­ground cav­erns that ab­sorbed an­cient wa­ter on Mars. (Cour­te­sy PSI)

The sci­en­tists, led by the Tuc­son, Ariz.-based Plan­etary Sci­ence In­sti­tute, re­marked that sat­el­lite images seem to show a net­work of pits and troughs in the ar­ea.

“The ul­ti­mate fate and na­ture of the flu­id dis­charges has re­mained a mys­tery for more than 40 years,” said the re­search­ers in a state­ment re­leased this week. The find­ings are to ap­pear in the re­search jour­nal Geo­phys­i­cal Re­search Let­ters. The overall ev­i­dence sug­gests that “enor­mous vol­umes of catas­troph­ic” flood dis­charges could have filled cav­erns some two bil­lion years ago, the sci­en­tists added.

He­brus Valles is de­scribed as un­ique in that it pre­serves pris­tine land­forms at the ends of an out­flow chan­nel. Si­m­i­lar land­forms seem to be highly resur­faced or bur­ied in oth­er places on the Red Plan­et.

Sci­en­tists have turned up many lines of ev­i­dence point­ing to an­cient, and pos­sibly still ex­ist­ing, liq­uid wa­ter on Mars. Even vast an­cient oceans have been pro­posed. But where that wa­ter might have gone is a mys­tery that could bear on the ques­tion of wheth­er life might have in­hab­it­ed Mars, or even still does in some form.

The Plan­etary Sci­ence In­sti­tute group spec­u­lates mud vol­can­ism may have formed many Mar­tian cav­erns by ex­pel­ling gobs of un­der­ground ma­te­ri­als to the sur­face. Cav­erns formed this way tend to be un­sta­ble and collapse-prone, but not al­ways. Any cav­erns in the area of in­vest­i­ga­tion are likely to have de­vel­oped with­in per­ma­nently fro­zen ground, which would have held up over time, the sci­en­tists said.

Pos­si­ble cav­erns have been iden­ti­fied before on Mars, causing a stir thanks to their po­ten­tial as life habi­tats, noted the au­thors of the re­port, re­search sci­ent­ist J. Alex­is Palmero Ro­driguez of the Plan­etary Sci­ence In­sti­tute and col­leagues. The age and sizes of any cav­erns re­main un­cer­tain, but they may well have ex­isted over bil­lions of years, they added.

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Immense cavern networks may have swallowed up much of the water that once coursed over the Red Planet, scientists say. Researchers studied the Hebrus Valles, a channel in the surface of Mars presumed to have been carved out by water or other fluid. In particular they examined the terminal regions, where the channel formations seem to peter out. A question was just where the liquid might have gone after getting there. The scientists, led by theTucson, Ariz.-based Planetary Science Institute, remarked that satellite photos seem to show a network of pits and troughs in the area. “The ultimate fate and nature of the fluid discharges has remained a mystery for more than 40 years,” said the researchers in a statement released this week. The findings are to appear in the research journal Geophysical Research Letters. The overall evidence suggests that “enormous volumes of catastrophic” flood discharges could have filled caverns some two billion years ago, the scientists added. Hebrus Valles is described as unique in that it preserves pristine landforms located at the ends of an outflow channel. Similar landforms seem to be highly resurfaced or buried in other places on the Red Planet. Scientists have turned up many lines of evidence pointing to ancient, and possibly still existing, liquid water running on Mars. Even vast ancient oceans have been proposed. But where that water might have gone is a mystery that could bear on the question of whether life might have inhabited Mars, or even still does in some form. The Planetary Science Institute group speculates mud volcanism may have formed many Martian caverns by expelling gobs of underground materials to the surface. Caverns formed this way tend to be unstable and collapse-prone, but not always. The investigated Martian caverns seem to have developed within permanently frozen ground, which would have held up over time, the scientists said. Possible caverns have been identified on Mars, catching widespread attention because of their potential as habitats, the investigators noted. The age and sizes of any caverns remain uncertain, but they may well have existed over billions of years, members of the group said. The authors of the report are research scientist J. Alexis Palmero Rodriguez of the Planetary Science Institute and colleagues.