Page 47 - (DK) Eyewitness - Mars

ANCIENT LAKE AND VALLEY
Gusev Crater, at left, may be a former lake fed by the snaking
Ma’adim Vallis. The crater is about 100 miles (160 km) across
and is the landing site for the Spirit Rover. Impact features
within the crater have been filled and smoothed over, MEANDERING SEDIMENT
probably with sediment deposited by water from the 560-mile Comparisons with sediment formations on Earth suggest
(900 km) Ma’adim canyon. that this rockform southeast of Valles Marineris was
originally sand deposited in a liquid environment. The
Lost rivers of ancient days sediment’s loop shape appears to have been formed by a
meandering—winding—stream. Sediment hardens over
millions of years and turns to “sedimentary” rock. This
Scientists search for evidence of water on Mars by comparing Earth’s particular rockform is termed a “meander” and is
dried-up waterways with Martian features. Southwest Asia’s long- convincing evidence that water once flowed here.
empty river beds look much like dendritic—branching—channels
found on Mars. Other landforms indicating past water on Mars are
deposits of sediment seemingly left by enormous floods.

South Yemeni dendritic system

EMPTY STREAMS ON EARTH AND MARS
Scientists believe the above image shows an ancient river
drainage system on Mars. The branchlike network in the
image at right is a former river in South Yemen, one of the
driest places on Earth. Martian dendritic channels could have
been cut by water flowing under a protective cover of ice.

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