London: American scientists have found
further evidence that huge seas existed on Mars long ago, a
discovery they say has strengthened the belief that conditions
on the red planet were once favourable for the evolution of
A geological mapping project by researchers at the
Planetary Science Institute in Tucson found sedimentary
deposits in a region called Hellas Planitia which suggest a
large sea once stood there.
The 2,000 km-wide, 8km-deep Hellas basin is a giant
impact crater -- the largest such structure on Mars.
The researchers claimed their data support a lake
between 4.5 and 3.5 billion years ago at the site, the BBC
"This mapping makes geologic interpretations
consistent with previous studies, and constrains the timing of
these putative lakes to the early-middle Noachian period on
Mars," said Dr Leslie Bleamaster, a research scientist at the
Planetary Science Institute.
According to the researchers, fine-layered outcrops
around the eastern rim of Hellas are likely to be sedimentary
They were formed through the erosion and transport of
rock and soil from the Martian highlands into a standing body
The results support earlier studies of the western
part of the Hellas basin.
However, they said that further study of the region could
provide clues about where this water went and to how the
Martian climate changed over geological history.
The mapping effort used data from a number of instruments
aboard Nasa spacecraft, including the Viking orbiter, Mars
Global Surveyor and Mars Odyssey.
Some scientists believe that conditions on Mars were
more favourable for the evolution of life at this time than
they were on Earth.