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Co2 Flows Could Carve Mars Gullies

Springtime flow channels actively cutting through the snowpack in the gullies. At this point in the spring thaw, defrosting has removed the snowpack from the flat plateau and pit floor, but CO2 snow still fills the alcoves at the head of the gullies. In a number of the gullies, continuous dark threads show that an active flow has cut through or overlaid the snowpack. The very dark "threads" are not a feature of shading, but are instead due to a distinct albedo difference. Not all gullies are active in these images. Some remain unmarked, showing that the dark threads are not merely a topographic effect. We interpret that a thin stream of debris has flowed down the central channel of many of the gullies. The width of the active channel is a few pixels, at most. All images were acquired on the ascending leg of the orbit at around 01:40 local time with the "midnight" sun over the south pole.

Image details: M0903898 November 15, 1999, Ls = 244.8, image width 2.84 km, resolution 5.52 m/pixel; M0905128 November 20, 1999, Ls = 248.0, image width 2.83 km, resolution 5.52 m/pixel; M0906352 November 28, 1999, Ls = 252.6, image width 2.84 km, resolution 2.76 m/pixel (displayed at reduced scale). b: Line drawing of features interpreted from (a). In M0903898 an area of diffuse avalanching "A" contrasts to focused dark threads "T" in channel cores. In M0905128 several fine threads are seen, contrasting to the broader diffuse albedo feature in a fully defrosted channel "D." In M0906352, numerous threads are visible with an anastomosing geometry. Data courtesy of NASA/JPL/Malin Space Science Systems.

  • View Original Images via Catalogue Numbers
  • Melbourne - Jan 06, 2003
    An Australian geologist has identified what could be the first ever active flow of fluids through gullies on Mars.

    University of Melbourne geologist, Dr Nick Hoffman, identified recent gully and channel development near the polar regions of Mars from images taken by the Mars Global Surveyor spacecraft. But contrary to the majority of scientific opinion which suggests that such features were carved by liquid water, Hoffman says the flow is most likely frozen carbon dioxide.

    NASA is desperate to find signs of liquid water on Mars so they have a target for the next generation of Mars landers and rovers to go and search for life, but their search could prove fruitless if Hoffman's analysis of the images is correct.

    In the latest edition of the journal Astrobiology, Hoffman presents evidence for the flow events on Mars and demonstrates that there are substances other than water that can flow on Mars and that water is probably the least likely substance to do this. Hoffman says the channels he identified from the Surveyor images are more likely being carved by avalanches of carbon dioxide and associated debris.

    "The consequences of this for life on Mars are shattering. If similar mechanisms are responsible for all the recent gullies on Mars then the near surface life NASA is so desperately searching for may not exist," says Hoffman.

    "Without liquid water there cannot be life and despite recent reports of more and more ice on the Red Planet, NASA has yet to find liquid water," he says.

    Many NASA scientists are doubtful about Hoffman's observations, but at a meeting of the American Geophysical Union held last month, Hoffman says they struggled to find arguments against the evidence he presented.

    The Mars Gullies were discovered in 2001. Hoffman's analysis of the recent images shows that a patch of gullies near the South Pole shows signs of annual flow activity each Martian Spring.

    "In itself the observation of active flows is a dramatic discovery since no movement has yet been seen on Mars, except for some dry dust avalanches. The gullies are thought to be the most promising candidates for liquid water flows on modern Mars and many NASA researchers are suggesting ways in which they might be formed by liquid water, but nobody has yet seen the gullies in action," says Hoffman.

    Hoffman suggests NASA researchers missed these most exciting events happening in the gullies as they have been focussed on looking for liquid water in late summer.

    "In the Martian Spring, when carbon dioxide frost and snow at temperatures of minus130 degrees Centigrade still fill the valleys, flow events are occurring. The flows cut through the frost at temperatures that would turn battery acid into building stone," he says.

    "Nothing based on water can flow at these temperatures, so the culprit must be defrosting carbon dioxide.

    "But carbon dioxide doesn't melt on Mars; it boils directly from the solid (a process called 'sublimation'). Instead of a trickle or gush of liquid pouring down the gully, the flow appears to be a flurry of boiling dry ice avalanching down the gully. The boiling dry ice acts like a army of miniature hovercraft carrying a shower of sand, dust, and tumbling rocks down the slope, carving out the gullies as it goes.

    Related Links
    Nick Hoffman's White Mars Project
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    Dark Streaks On Martian Slopes May Signal Active Water
    Tucson - Dec 19, 2002
    Salty water driven by hot magma from Mars' deep interior may be forming some of the mysterious dark slope streaks visible near the Red Planet's equator, according to University of Arizona scientists.



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