Recently unavailable in
supporting the successful landing of the Curiosity rover of the Mars Science
Laboratory, NASA, ESA's Mars Express has now returned to its primary mission to
study the varied geology and atmosphere "Red Planet" from orbit.
Earlier this year, the
spacecraft observed the Hadley crater 120 km wide,
providing exciting insights into the Martian crust. The images show multiple subsequent impacts within the wall of the main crater depths up to 2600 m below the surrounding surface.
The imaged region 9
April 2012 by the HRSC (High Resolution Stereo Camera) on Mars Express shows
the crater that is located to the west of Al-Qahira Vallis in the transition
zone between the oldest mountains in the south and younger northern plains.
Hadley is named after
British lawyer and meteorologist George Hadley (1685-1768), whose name was also
awarded the "Hadley cell", a circulation system in the atmosphere,
which transports heat and the humidity of the tropics to higher latitudes.
The images show that
the crater Hadley was repeatedly hit by large asteroids and / or comets after
its initial formation and is subsequently filled with lava and sediment.
Some of these
subsequent impacts were also partially buried, with subtle clues of a number of
edges of the crater to the west (top), wrinkles and ridges to the north (right
side) of the main crater floor as shown in the image.
Again, in the image on
the south side (left), the crater is shallower than the opposite side. This
difference can be explained by a process of erosion known as mass movement.
This is where the surface material moving on a slope under the force of
gravity.
Mass movements can be
initially triggered by a series of processes, including earthquakes, erosion at
the base of the slope, the separation of the ice or water introduced into the
rock material in sloping. In this case, there is no clear indication of the
process that caused it, or what time it took place.
Of particular interest
to scientists studying the geology of Mars ejecta craters are smaller in
Hadley. Two of them, one in the west (top), and the deepest in the middle of
the image, show traces of volatiles, possibly water ice beneath the surface.
With impact craters
that form this ice mix with the surrounding material to form a sort of
"mud", which would then be distributed over the surface as the
ejecta.
Scientists believe that
these birds were excavated by impacts, may indicate the presence of ice on a
depth of several hundred meters, this being the difference in depth between the
surface and the depths of the two craters.
This view deep in the
Martian crust in the walls of the crater Hadley provides scientists with an
overview of the history of Mars. A story vagrants as those currently on the Red
Planet and others that will follow are likely to continue studying.
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