Evidence for ancient glaciation on Pluto
by Staff Writers
Mountain View CA (SPX) Nov 14, 2018
A letter authored by SETI Institute scientist Oliver White was published by Nature Astronomy today. Co-authors included researchers Jeff Moore, Tanguy Bertrand and Kimberly Ennico at NASA's Ames Research Center in Silicon Valley.
The letter "Washboard and Fluted Terrains on Pluto as Evidence for Ancient Glaciation" focuses on these distinctive landscapes that border the vast nitrogen ice plains of Sputnik Planitia along its northwest margin (Figure 1) and which are amongst the most enigmatic landforms yet seen on Pluto. These terrains consist of parallel to sub-parallel ridges that display a remarkably consistent ENE-WSW orientation, a configuration that does not readily point to a simple analogous terrestrial or planetary process or landform.
The aim of Dr. White's research is to use mapping and analysis of the morphometry (the process of measuring the external shape and dimensions of landforms) and distribution of the ridges to determine their origin and to understand their significance within the overall geologic history of Pluto. The work used imaging data returned by NASA's New Horizons spacecraft, which flew past Pluto in 2015, as well as topographic maps generated from this data.
Washboard and fluted ridges are defined primarily by their topographic context: washboard ridges occur in level settings within valley floors, basins and uplands, whereas fluted ridges are seen on steeper spurs, massifs (or compact group of mountains) and crater walls that separate basins and valleys.
The washboard and fluted terrain is seen up close in Figure 2, in which illumination is from the top. They occur at the location on Sputnik Planitia's perimeter where elevations and slopes leading into the surrounding uplands are lowest, and also where a major tectonic system coincides with the edge of Sputnik Planitia.
The low elevation of the area makes it a natural setting for past coverage by nitrogen ice glaciers, as indicated by modeling of volatile behavior on Pluto performed by Dr. Bertrand at Ames. Through comparison of the washboard and fluted texture with parallel chains of elongated sublimation pits (depressions in the surface formed where ice turns directly into a gas) seen in southern Sputnik Planitia, the ridges are interpreted to represent water ice debris liberated by tectonism of underlying crust.
This water ice debris was buoyant in the denser, pitted glacial nitrogen ice that is interpreted to have formerly covered this area, and collected on the floors of the elongated pits. After the nitrogen ice receded via sublimation, the debris was left as the aligned ridges, mimicking the sublimation texture - washboard ridges where deposited on flat terrain, and fluted ridges where deposited on steeper slopes.
Crater surface age estimates indicate that the washboard and fluted ridges were deposited early in Pluto's history, after formation of the Sputnik basin by a giant impact ~4 billion years ago. Acting as a giant cold trap, it was to this basin that surface nitrogen ice across Pluto migrated over some tens of millions of years, thereby causing the recession of nitrogen glaciers from upland areas such as that now occupied by the washboard and fluted terrain.
The precise mechanism that elongated the sublimation pits and defined their strikingly consistent orientation regardless of latitude or location relative to Sputnik Planitia is elusive, but is consistent with a global-scale process.
A constraint is that true polar wander solutions for Pluto (provided by co-author Dr. James Keane of Caltech) indicate that the ridges can never have all been oriented N-S at any time in Pluto's history. This suggests a cause for the alignment that is not exogenic (i.e. the orientation is likely not governed solely by solar illumination, which would cause all the sublimation pits to align N-S).
Dr. White summarizes the findings as follows: "These terrains constitute an entirely new category of glacial landform that is unique to Pluto, and represent geological evidence that nitrogen ice glaciation was more widespread across Pluto in its early history prior to the formation of the Sputnik basin. The dense spacing of the ridges allows us to precisely map out the past coverage of the glaciation that deposited them, which extended across at least 70,000 km^2 of Pluto's uplands (larger than the state of West Virginia)."
Research Report: "Washboard and Fluted Terrains on Pluto as Evidence for Ancient Glaciation," Oliver L. White et al., 2018 Nov. 12, Nature Astronomy
SwRI team makes breakthroughs studying Pluto orbiter mission
San Antonio TX (SPX) Oct 25, 2018
A Southwest Research Institute team using internal research funds has made several discoveries that expand the range and value of a future Pluto orbiter mission. The breakthroughs define a fuel-saving orbital tour and demonstrate that an orbiter can continue exploration in the Kuiper Belt after surveying Pluto. These and other results from the study will be reported this week at a workshop on future Pluto and Kuiper Belt exploration at the American Astronomical Society's Division for Planetary Sciences ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.