[meteorite-list] NASA Spacecraft Data Suggest Water Flowing On Mars (MRO)

[Ron Baalke]

August 04, 2011

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

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

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


RELEASE: 11-245

NASA SPACECRAFT DATA SUGGEST WATER FLOWING ON MARS

WASHINGTON -- Observations from NASA's Mars Reconnaissance Orbiter 
(MRO) 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 MRO 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. 

MRO 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. 

For more information about MRO, visit: 

http://www.nasa.gov/mro   
	
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