[meteorite-list] MRO Reveals Details of a Wetter Mars

[Ron Baalke]

Oct. 28, 2008

Dwayne Brown 
Headquarters, Washington 
202-358-1726 
dwayne.c.brown at nasa.gov 

Jennifer Huergo 
Johns Hopkins University Applied Physics Laboratory, Laurel, Md. 
240-228-5618 
jennifer.huergo at jhuapl.edu 

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-6278 
guy.webster at jpl.nasa.gov 
RELEASE: 08-273

NASA ORBITER REVEALS DETAILS OF A WETTER MARS

WASHINGTON -- NASA's Mars Reconnaissance Orbiter has observed a new 
category of minerals spread across large regions of Mars. This 
discovery suggests that liquid water remained on the planet's surface 
a billion years later than scientists believed, and it played an 
important role in shaping the planet's surface and possibly hosting 
life. 

Researchers examining data from the orbiter's Compact Reconnaissance 
Imaging Spectrometer for Mars have found evidence of hydrated silica, 
commonly known as opal. The hydrated, or water-containing, mineral 
deposits are telltale signs of where and when water was present on 
ancient Mars. 

"This is an exciting discovery because it extends the time range for 
liquid water on Mars, and the places where it might have supported 
life," said Scott Murchie, the spectrometer's principal investigator 
at the Johns Hopkins University Applied Physics Laboratory in Laurel, 
Md. "The identification of opaline silica tells us that water may 
have existed as recently as 2 billion years ago." 

Until now, only two major groups of hydrated minerals, phyllosilicates 
and hydrated sulfates, had been observed by spacecraft orbiting Mars. 
Clay-like phyllosilicates formed more than 3.5 billion years ago 
where igneous rock came into long-term contact with water. During the 
next several hundred million years, until approximately 3 billion 
years ago, hydrated sulfates formed from the evaporation of salty and 
sometimes acidic water. 

The newly discovered opaline silicates are the youngest of the three 
types of hydrated minerals. They formed where liquid water altered 
materials created by volcanic activity or meteorite impact on the 
Martian surface. One such location noted by scientists is the large 
Martian canyon system called Valles Marineris. 

"We see numerous outcrops of opal-like minerals, commonly in thin 
layers extending for very long distances around the rim of Valles 
Marineris and sometimes within the canyon system itself," said Ralph 
Milliken of NASA's Jet Propulsion Laboratory in Pasadena, Calif. 

Milliken is lead author of an article in the November issue of 
"Geology" that describes the identification of opaline silica. The 
study reveals that the minerals, which also were recently found in 
Gusev Crater by NASA's Mars rover Spirit, are widespread and occur in 
relatively young terrains. 

In some locations, the orbiter's spectrometer observed opaline silica 
with iron sulfate minerals, either in or around dry river channels. 
This indicates the acidic water remained on the Martian surface for 
an extended period of time. Milliken and his colleagues believe that 
in these areas, low-temperature acidic water was involved in forming 
the opal. In areas where there is no clear evidence that the water 
was acidic, deposits may have formed under a wide range of 
conditions. 

"What's important is that the longer liquid water existed on Mars, the 
longer the window during which Mars may have supported life," says 
Milliken. "The opaline silica deposits would be good places to 
explore to assess the potential for habitability on Mars, especially 
in these younger terrains." 

The spectrometer collects 544 colors, or wavelengths, of reflected 
sunlight to detect minerals on the surface of Mars. Its highest 
resolution is about 20 times sharper than any previous look at the 
planet in near-infrared wavelengths. 

NASA's Jet Propulsion Laboratory manages the Mars Reconnaissance 
Orbiter mission for NASA's Science Mission Directorate in Washington. 
Lockheed Martin Space Systems, Denver, is the prime contractor for 
the project and built the spacecraft. The Applied Physics Laboratory 
led the effort to build the spectrometer and operates the instrument 
in coordination with an international team of researchers from 
universities, government and the private sector. 

For more about the Mars Reconnaissance Orbiter, visit: 

http://www.nasa.gov/mro   
	
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