Washington: American scientists claim to have
found evidence that suggests Mars had a warm and wet climate
which could have supported life some 3.5 billion years ago.
A team led by planetary geologists at Brown University
found mounds of a mineral deposited on a volcanic cone less
than 3.5 billion years ago that speak of a warm and wet past
and may preserve evidence of one of the most recent habitable
microenvironments on the red planet.
Observations by NASA`s Mars Reconnaissance Orbiter enabled
the researchers to identify the mineral as hydrated silica
which can be dissolved, transported and concentrated by hot
water or steam -- a dead ringer that water was present at some
time.
The mineral and the mounds` location on the flanks of a
volcanic cone provide the best evidence yet found on Mars for
an intact deposit from a hydrothermal environment -- a steam
fumarole or a hot spring, said the researchers.
Such environments might have provided habitats for some
of Earth`s earliest life forms, they hoped.
"The heat and water required to create this deposit
probably made this a habitable zone," said J R Skok, lead
author of the study, published in journal Nature Geoscience.
"If life did exist there, this would be a promising spot
where it would have been entombed -- a microbial mortuary, so
to speak."
No studies have determined whether Mars has ever supported
life, but this finding adds to accumulating evidence that at
some times and in some places, Mars hosted favourable climate
for microbial life.
The deposit is located in the sprawling, flat volcanic
zone known as Syrtis Major and was believed to have been left
during the early Hesperian period, when most of Mars was
already turning chilly and arid.
"Mars is just drying out," Skok said, "and this is one
last hospitable spot in a cooling, drying Mars."
Concentrations of hydrated silica have been identified on
Mars previously, including a nearly pure patch found by NASA`s
Mars Exploration Rover Spirit in 2007. However, this is the
first found in an intact setting that clearly signals the
mineral`s origin.
"You have spectacular context for this deposit," Skok
said. "It`s right on the flank of a volcano. The setting
remains essentially the same as it was when the silica was
deposited."
Observations by cameras on the Mars Reconnaissance
Orbiter revealed patches of bright deposits near the summit of
the cone, fanning down its flank, and on flatter ground in the
vicinity.
The Brown researchers partnered with Scott Murchie of
Johns Hopkins University Applied Physics Laboratory to analyze
the bright exposures with the Compact Reconnaissance Imaging
Spectrometer for Mars (CRISM) instrument on the orbiter.
Hydrated silica identified by the spectrometer in uphill
locations -- confirmed by stereo imaging -- indicates that hot
springs or fumaroles fed by underground heating created these
deposits. Silica deposits around hydrothermal vents in Iceland
are among the best parallels on Earth.
"The habitable zone would have been within and alongside
the conduits carrying the heated water," Murchie said.
PTI
