July 30, 2012
New Evidence Of Water On Mars: Polygons Could Be The Key
Brett Smith for redOrbit.com - Your Universe Online
Images taken in 2008 stirred excitement among scientists when they received the first detailed glimpses of large polygon formations along the Martian surface.
An article published in the GSA Today, takes a closer look at the possible causes of these formations and their potential connection to similar formations along the ocean floor here on Earth, reinforcing the possibility of liquid covering the Martian surface at some point in the past.
Researchers from the University of Texas at Austin, who wrote the piece, poured over NASA images culled from various missions to the red planet over the past 47 years, including pictures from Mariner, Viking, THEMIS, and MOLA. These scientists were more interested in studying the large polygons that span the northern plains of Mars, as opposed to the smaller polygon-shaped bodies found elsewhere on Mars that are explained by thermal contraction processes similar to those found in Earth´s polar permafrost environments.
These larger polygons, which can measure over a kilometer in diameter, closely resemble deep-sea formations created by faults and are common in fine-grained, deep-sea sediments found in the North Sea and the Norwegian Sea. Images of the terrestrial polygons are commonly taken during 3-D seismic surveys conducted while searching for offshore fossil fuel deposits. These seismic surveys that have become commonplace in the drilling industry and have also allowed scientists to study terrestrial, deep-sea environments like never before.
The University of Texas team, led by Lorena Moscardelli, suggests in their study that both of these sets of polygons are formed by a similar mechanism: deep ocean sediment and debris flows.
To support this theory, the report points out that “large-scale Martian basinal polygons are preserved where slopes were low” compared to “(i)ntact, deep-water, polygonal fault systems(that) are also preserved on Earth on gentle slopes.”
Gentle slopes along the ocean floor also led to the polygons with the most regular shapes and sizes, according to the study. Areas along the ocean floor with steep slopes contain polygons that were either altered or irregular. The influence of a gently sloping marine environment is consistent with the behavior of the soft clay sediments as they creep or flow down slopes in these areas.
These observations on deep sea polygons are consistent with those on Martian polygons. In the northern plains area of Mars–polygons are quite regularly shaped and sized. Areas of more varied Martian topography contain broken and disrupted shapes.
The researchers noted that formation of the ocean polygons require fine-grained, slightly buried clay sediments in ocean basins deeper than 500 meters. The report also cited an observation made recently by Michelle Cooke at the University of Massachusetts–the physical mechanism of polygon creation involves a thick, wet, and mechanically fragile layer of sediment.
Based on these similarities, the Texas research team concludes that these features found on different planets in completely different environments share a common marine origin and creation mechanism. Therefore, these geometric features provide further evidence for the existence of a deep-ocean that spanned the northern portion of Mars around three billion years ago.