Debate over the origin of large-scale polygons (hundreds of meters to kilometers in diameter) on Mars remains active even after several decades of detailed observations. Similarity in geometric patterns on Mars and Earth has long captured the imagination.
In this new article from GSA Today, geologists at The University of Texas at Austin examine these large-scale polygons and compare them to similar features on Earth's seafloor, which they believe may have formed via similar processes.
Understanding these processes may in turn fuel support for the idea of ancient oceans on Mars.
Through examination of THEMIS, MOLA, Viking, and Mariner data and images, planetary scientists have found that areas on the northern plains of Mars are divided into large polygon-shaped portions and that sets of these polygons span extensive areas of the Martian surface. Smaller polygon-shaped bodies are found elsewhere on Mars, but these are best explained by thermal contraction processes similar to those in terrestrial permafrost environments and not likely to form larger polygons.
In the August 2012 issue of GSA Today, Lorena Moscardelli and her colleagues from The University of Texas at Austin present a detailed comparison of the geometric features of these large Martian polygons and similar features found in deep-sea sediments here on Earth. Moscardelli and colleagues note striking similarities.
On Earth, polygon-shaped areas, with the edges formed by faults, are common in fine-grained deep-sea sediments. Some of the best examples of these polygon-fault areas are found in the North Sea and the Norwegian Sea. These are imaged using detailed, 3-D seismic surveys conducted to search for offshore oil and gas deposits. Images reproduced in this paper show that these deep-water polygons are also 1,000 meters or greater in diameter.
While the details of deep-sea polygon formation on Earth are complex, Moscardelli and her colleagues conclude that the majority of these polygons form in a common environment: sediments made up of fine-grained clays in ocean basins that are deeper than 500 meters, and when these sediments are only shallowly buried by younger sediments. A key observation -- also made recently by Michelle Cooke at the University of Massachusetts -- is that the physical mechanism of polygon formation requires a thick, wet, and mechanically weak layer of sediment.
Moscardelli and colleagues also conclude that the slope angle of the sea floor plays an important role in both the formation and preservation of these polygons. Where the seafloor slope is very gentle (slopes less than half a degree), the polygons have very regular shapes and sizes. In many locations where polygons have formed on top of buried topographic features on the seafloor, the shapes of the polygons were altered, and in some cases were broken up and disrupted where the slopes were steepest. Both observations are consistent with deformation of the soft marine sediments as they creep or flow downslope in these areas.
In the northern plains of Mars, where the surface is basically flat, the polygons have very regular shapes and sizes -- remarkably similar to the deep-sea polygons found on Earth. In places where the topography on Mars is more varied, and where there may be evidence for other sediment-transport features on the surface, areas of deformed and disrupted polygons can be found -- again similar to the disrupted polygons here on Earth.
On the basis of these striking similarities, the University of Texas at Austin team concludes that these features most likely share a common origin and were formed by similar mechanisms in a similar environment. The team argues that the Martian polygons were formed within a thick, wet, and weak layer of fine-grained sediments that were deposited in a deep-water setting, similar to the Earth polygons. Thus, these interesting geometric features may provide additional evidence for the existence of an ocean in the northern portion of Mars approximately three billion years ago.
GSA Today articles are open access online; for a print copy, please contact Kea Giles at the e-mail address. Please discuss articles of interest with the authors before publishing stories on their work, and please make reference to GSA Today in articles published.
Deep-water polygonal fault systems as terrestrial analogs for large-scale Martian polygonal terrains Lorena Moscardelli, Tim Dooley, Dallas Dunlap, Martin Jackson, and Lesli Wood, Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713-8924, USA. Pages 1-9; doi: 10.1130/GSATG147A.1, www.geosociety.org/gsatoday/archive/22/8/.
GSA Today is The Geological Society of America's science and news magazine for members and other earth scientists. Refereed lead science articles present exciting new research or synthesize important issues in a format understandable to all in the earth science community. GSA Today often features a refereed "Groundwork" articles -- tightly focused papers on issues of import to earth science policy, planning, funding, or education. All GSA Today articles are open access at www.geosociety.org/pubs/
Kea Giles | EurekAlert!
Mountain glaciers shrinking across the West
23.10.2017 | University of Washington
Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen
Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Life Sciences
23.10.2017 | Physics and Astronomy
23.10.2017 | Health and Medicine