Apart
from impact cratering, which must be continuing to the present day, the
youngest event identified in Mercury's global record is the formation of
a number of sinuous features known as lobate scars. These range from 20
to 500 km in length, and up to 2 km in height. They are regarded as unmistakable
signs of compression of Mercury's lithosphere, indicating where the edge
of a tract of lithosphere has been thrust over an adjacent tract. |
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Summing
up the deformation indicated by all the observed lobate scars indicates
a reduction in Mercury's radius of between 1 and 2 km. This would have been
caused either by contraction of Mercury's mantle as it cooled, or by solidification
of a previously liquid part of the core. |
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