AFP/NASA – An undated handout photo of a view of the north polar region
of Mars from orbit. Astronomers on Wednesday …
Huge troughs curving outward from the north pole of Mars
like the arms of a pinwheel were not carved into the polar ice caps by some
mysterious force, researchers have discovered. Instead, the shifting pattern
arose from a long process of formation and erosion that gave it the appearance
of slowly moving and spiraling inward over time.
A similarly snail-like process gave rise to the Chasma
Boreale canyon that cuts into the side of the giant pinwheel pattern, known as
the north polar layered deposits (NPLD). The unveiling of the origins of the
canyon and NPLD came courtesy of ground-penetrating radar carried by two
Mars orbiters.
Scientists had previously favored the idea that a natural
force recently carved both the canyon and pinwheel pattern into older geological
deposits. But they could not test their theories beyond what they could see on
the Martian surface, as if trying to judge a book by its cover.
"Radar is like opening the book; we can read each page
now," said Isaac Smith, a planetary scientist at the University of Texas
Austin. "People were looking at the outside and thinking they knew what
the book was about, but they didn't."
Such technology allowed scientists
to take 2-D cross-section images of the troughs and reveal the layers within
the walls, like snapshots in time going back through the red planet's history.
Radar also helped trace reflective markers that followed the geometry of
underground structures to build up a 3-D sense of the layers.
The radar studies do not answer the riddle of what changes
in the Martian atmosphere spurred the formation of both the canyon and the
younger spiraling troughs. But they do give scientists a new understanding of
the timing of the processes that allow the wind and sun to shape the Martian
surface over a certain period, and that may lead to more evidence-based climate
models for the red planet
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