News: Study Reveals Young Mars Was A Wet World
- From: Ye Old One <usenet@xxxxxxxxx>
- Date: Fri, 21 Apr 2006 12:53:16 GMT
Study Reveals Young Mars Was A Wet World
http://news.yahoo.com/s/space/20060420/sc_space/studyrevealsyoungmarswasawetworld
Ker Than
Staff Writer
SPACE.com Thu Apr 20, 3:00 PM ET
The most comprehensive study ever conducted of minerals on Mars'
surface reveals the planet has undergone three distinct geological
eras throughout its history, with water playing a progressively lesser
role in each.
If life as we know it here on Earth ever existed on the red planet, it
could only have survived in the planet's infancy, during the earliest
era, the study concludes.
"Starting about 3.5 billion years ago, conditions on Mars became
increasingly dry and acidic--not a pleasant place for any form of
life, even a microbe," said study team member John Mustard, a
geologist from Brown University.
The mineral maps were created using data from OMEGA, the major
spectrometer aboard the Mars Express, as well as related observations
collected by other Mars orbiters and the two rovers.
The study, led by Jean-Pierre Bibring from the University of Paris, is
detailed in the March 21 issue of the journal Science.
The three faces of Mars
Based on their analyses, the team divided Mars' geological history
into three distinct eras:
The first era, which lasted from about 4.6 billion years ago to 4
billion years ago, was a relatively wet one. The oldest rock--exposed
by erosion, impact or faulting--showed the presence of clay minerals,
such as chamosite and nontronite, that require abundant water,
moderate temperatures and low acidity to form.
The next era was drastically different. Massive volcanic eruptions
spewed sulfur into the atmosphere, turning the planet's moist and
alkaline environment to a dry, acidic one. This period lasted form
about 4 and 3.5 billion years and is evidenced by minerals such as
gypsum and grey hematite, which were found in Meridiani and in Valles
Marineris.
Minerals from the most recent era, which began about 3.5 billion years
ago and continues to the present, show no evidence of forming with, or
being altered by, liquid water. These iron-rich minerals, mostly
ferric oxides, were found across most of the planet and reflect the
cold, dry conditions that persist on Mars to this day.
The new study also revealed what is responsible for Mar's reddish hue:
most likely, the researchers say, the red planet gets its color from
tiny grains of red hematite or possibly maghemite, two minerals that
are riddled with iron.
A target for future mission
If Martian life ever did exist, it could probably have only survived
during the first era, the team reports. And evidence for that life is
most likely to be found in the Syrtis Major volcanic plateau, in Nili
Fossae and in the Marwth Vallis Regions, two regions rich in the clay
minerals abundant during Mars' youth. The researchers added that these
areas would make compelling targets for future lander missions.
--
Bob.
.
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