NASA Orbiter Reveals Details of a Wetter Mars
PASADENA, Calif. -- 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
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
"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.
More information about the Mars Reconnaissance Orbiter is at http://www.nasa.gov/mro
Media contacts: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Jennifer Huergo 240-228-5618
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.