Oblique View of Warm Season Flows in Newton Crater
An image combining orbital imagery with 3-D modeling shows flows that appear in spring and summer on a slope inside Mars' Newton crater.
PASADENA, Calif. -- Observations from NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.

"NASA's Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form,” NASA Administrator Charles Bolden said, “and it reaffirms Mars as an important future destination for human exploration."

Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars' southern hemisphere.

"The best explanation for these observations so far is the flow of briny water," said Alfred McEwen of the University of Arizona, Tucson. McEwen is the principal investigator for the orbiter's High Resolution Imaging Science Experiment (HiRISE) and lead author of a report about the recurring flows published in Thursday's edition of the journal Science.

Some aspects of the observations still puzzle researchers, but flows of liquid brine fit the features' characteristics better than alternate hypotheses. Saltiness lowers the freezing temperature of water. Sites with active flows get warm enough, even in the shallow subsurface, to sustain liquid water that is about as salty as Earth's oceans, while pure water would freeze at the observed temperatures.

"These dark lineations are different from other types of features on Martian slopes," said Mars Reconnaissance Orbiter Project Scientist Richard Zurek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Repeated observations show they extend ever farther downhill with time during the warm season."

The features imaged are only about 0.5 to 5 yards or meters wide, with lengths up to hundreds of yards. The width is much narrower than previously reported gullies on Martian slopes. However, some of those locations display more than 1,000 individual flows. Also, while gullies are abundant on cold, pole-facing slopes, these dark flows are on warmer, equator-facing slopes.

The images show flows lengthen and darken on rocky equator-facing slopes from late spring to early fall. The seasonality, latitude distribution and brightness changes suggest a volatile material is involved, but there is no direct detection of one. The settings are too warm for carbon-dioxide frost and, at some sites, too cold for pure water. This suggests the action of brines, which have lower freezing points. Salt deposits over much of Mars indicate brines were abundant in Mars' past. These recent observations suggest brines still may form near the surface today in limited times and places.

When researchers checked flow-marked slopes with the orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), no sign of water appeared. The features may quickly dry on the surface or could be shallow subsurface flows.

"The flows are not dark because of being wet," McEwen said. "They are dark for some other reason."

A flow initiated by briny water could rearrange grains or change surface roughness in a way that darkens the appearance. How the features brighten again when temperatures drop is harder to explain.

"It's a mystery now, but I think it's a solvable mystery with further observations and laboratory experiments," McEwen said.

These results are the closest scientists have come to finding evidence of liquid water on the planet's surface today. Frozen water, however has been detected near the surface in many middle to high-latitude regions. Fresh-looking gullies suggest slope movements in geologically recent times, perhaps aided by water. Purported droplets of brine also appeared on struts of the Phoenix Mars Lander. If further study of the recurring dark flows supports evidence of brines, these could be the first known Martian locations with liquid water.

The Mars Reconnaissance Orbiter is managed by JPL for NASA's Science Mission Directorate in Washington. The University of Arizona's Lunar and Planetary Laboratory operates HiRISE. The camera was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Johns Hopkins University Applied Physics Laboratory in Laurel, Md., provided and operates CRISM. JPL is a division of the California Institute of Technology in Pasadena.

For more information about the Mars Reconnaissance Orbiter, visit: http://www.nasa.gov/mro and http://marsprogram.jpl.nasa.gov/mro/.

  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of Horowitz crater, at 32 degrees south latitude, 141 degrees east...

    more
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    This map of Mars shows relative locations of three types of findings related to salt or frozen water, plus a new type of finding that may be related to both salt and water.

    Coloring of the map is coded to concentrations of shallow subsurface water ice found by the Gamma Ray Spectrometer - Neutron Spectrometer on NASA's Mars Odyssey orbiter....

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    Unfrozen brine in cryopegs and fracture networks provides habitats for the survival and growth of organisms both within and under frozen rocky materials on Earth and, by analogy, could provide habitats on Mars. Cryopegs are isolated lenses or pockets of highly saline, liquid water that is permanently subzero (Celsius) in temperature due to...

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  • An image combining orbital imagery with 3-D modeling shows flows that appear in spring and summer on a slope inside Mars' Newton crater.

    An image combining orbital imagery with 3-D modeling shows flows that appear in spring and summer on a slope inside Mars' Newton crater. Sequences of observations recording the seasonal changes at this site and a few others with similar flows might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation...

    more
  • This image contrasts gullies and recurring warm-season slope flows appearing in the same crater, in the middle southern latitudes of Mars.

    This image contrasts gullies and recurring warm-season slope flows appearing in the same crater, in the middle southern latitudes of Mars. It was taken Nov. 27, 2007, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.

    Gullies are on the pole-facing slope, which is on the northern side of this...

    more
  • This image contrasts gullies and recurring warm-season slope flows appearing in the same crater, in the middle southern latitudes of Mars.

    This image contrasts gullies and recurring warm-season slope flows appearing in the same crater, in the middle southern latitudes of Mars. It was taken Nov. 27, 2007, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.

    Gullies are on the pole-facing slope, which is on the northern side of this...

    more
  • This image shows warm-season flows on a north-facing slope in middle southern latitudes of Mars.

    This image shows warm-season flows on a north-facing slope in middle southern latitudes of Mars. It was taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter on June 24, 2011. The season was summer in Mars' southern hemisphere.

    The flow features are narrow (one-half to five yards or meters...

    more
  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of Newton crater, at 41.6 degrees south latitude, 202.3 degrees east...

    more
  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of Newton crater, at 41.6 degrees south latitude, 202.3 degrees east...

    more
  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of Newton crater, at 41.6 degrees south latitude, 202.3 degrees east...

    more
  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of Horowitz crater, at 32 degrees south latitude, 141 degrees east...

    more
  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of a steep crater slope in the Terra Cimmeria region of Mars, at 38.8...

    more
  • This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today.

    This series of images shows warm-season features that might be evidence of salty liquid water active on Mars today. Evidence for that possible interpretation is presented in a report by McEwen et al. in the Aug. 5, 2011, edition of Science.

    These images come from observations of a well-preserved crater in the Terra Sirenum region of Mars, at...

    more
  • This back and forth comparison shows changes that occurred in a gully on a south-facing slope in middle southern latitudes of Mars.

    This back and forth comparison shows changes that occurred in a gully on a south-facing slope in middle southern latitudes of Mars. Such changes in gullies on Mars, unlike changes in a recently discovered class of active slope features, have not been linked to warm seasons.

    Both images in this pair were taken by the High Resolution Imaging...

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2011-242

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov

Steve Cole 202-358-0918
NASA Headquarters, Washington
stephen.e.cole@nasa.gov

Daniel Stolte 520-626-4402
University of Arizona, Tucson
stolte@email.arizona.edu

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