Nasa’s Curiosity rover has discovered gravel – rock
fragments and pebbles – once carried by the waters of an ancient stream.
The stream must have run vigorously through the area, the US space
agency said.
Scientists had previously found other
evidence of the presence of water at one time on the Red Planet, but
this is the first time stream bed gravel has been discovered.
The
pictures transmitted by Curiosity show the pebbles have been cemented
into layers of rock at a site between the north rim of the Gale Crater
and the base of Mount Sharp, where Curiosity is heading.
The
sizes and the shapes of the rocks give an idea of the speed and the
depth of the stream, NASA said. “The shapes tell you they were
transported, and the sizes tell you they couldn’t be transported by
wind. They were transported by water flow,” said Curiosity science
co-investigator Rebecca Williams.
The scientists estimate the water was moving at a brisk three feet per second and ran somewhere between ankle and hip deep.
Some
of the rocks are rounded, indicating they travelled a long distance
from above the rim, fed from a channel named ‘Peace Vallis’, NASA said.
Two
rocky outcrops called ‘Hottah’ and ‘Link’ could have been ancient river
beds. Based on imagery previously captured by satellites, the
scientists said they can see channels that probably flowed uphill of
Link and Hottah.
The high number of channels between
the rim and the newly-discovered rock bed suggests the stream wasn’t a
one-time occurrence, but that many streams flowed or repeated over a
long time.
Curiosity is on a two-year mission to
investigate whether life is possible on Mars and to learn whether
conditions there might have been able to support life in the past.AFP
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