Pub Date : 2014-01-01Epub Date: 2014-08-21DOI: 10.1186/s13535-014-0003-4
Jason W Barnes, Christophe Sotin, Jason M Soderblom, Robert H Brown, Alexander G Hayes, Mark Donelan, Sebastien Rodriguez, Stéphane Le Mouélic, Kevin H Baines, Thomas B McCord
Cassini/VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of [Formula: see text] cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.
{"title":"<i>Cassini</i>/VIMS observes rough surfaces on Titan's Punga Mare in specular reflection.","authors":"Jason W Barnes, Christophe Sotin, Jason M Soderblom, Robert H Brown, Alexander G Hayes, Mark Donelan, Sebastien Rodriguez, Stéphane Le Mouélic, Kevin H Baines, Thomas B McCord","doi":"10.1186/s13535-014-0003-4","DOIUrl":"https://doi.org/10.1186/s13535-014-0003-4","url":null,"abstract":"<p><p><i>Cassini</i>/VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of [Formula: see text] cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.</p>","PeriodicalId":91593,"journal":{"name":"Planetary science","volume":"3 ","pages":"3"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s13535-014-0003-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34359945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01Epub Date: 2014-04-04DOI: 10.1186/s13535-014-0002-5
James G Williams, Slava G Turyshev, Dale H Boggs
Tides induce a semimajor axis rate of +38.08 ± 0.19 mm/yr, corresponding to an acceleration of the Moon's orbital mean longitude of -25.82 ± 0.13 "/cent2, as determined by the analysis of 43 yr of Lunar Laser Ranging (LLR) data. The LLR result is consistent with analyses made with different data spans, different analysis techniques, analysis of optical observations, and independent knowledge of tides. Plate motions change ocean shapes, and geological evidence and model calculations indicate lower rates of tidal evolution for extended past intervals. Earth rotation has long-term slowing due to tidal dissipation, but it also experiences variations for times up to about 105 yr due to changes in the moment of inertia. An analysis of LLR data also tests for any rate of change in either the speed of light c or apparent mean distance. The result is (-2.8 ± 3.4)×10-12 /yr for either scale rate or -(dc/dt)/c, or equivalently -1.0 ± 1.3 mm/yr for apparent distance rate. The lunar range does not reveal any change in the speed of light.
{"title":"The past and present Earth-Moon system: the speed of light stays steady as tides evolve.","authors":"James G Williams, Slava G Turyshev, Dale H Boggs","doi":"10.1186/s13535-014-0002-5","DOIUrl":"https://doi.org/10.1186/s13535-014-0002-5","url":null,"abstract":"<p><p>Tides induce a semimajor axis rate of +38.08 ± 0.19 mm/yr, corresponding to an acceleration of the Moon's orbital mean longitude of -25.82 ± 0.13 \"/cent<sup>2</sup>, as determined by the analysis of 43 yr of Lunar Laser Ranging (LLR) data. The LLR result is consistent with analyses made with different data spans, different analysis techniques, analysis of optical observations, and independent knowledge of tides. Plate motions change ocean shapes, and geological evidence and model calculations indicate lower rates of tidal evolution for extended past intervals. Earth rotation has long-term slowing due to tidal dissipation, but it also experiences variations for times up to about 10<sup>5</sup> yr due to changes in the moment of inertia. An analysis of LLR data also tests for any rate of change in either the speed of light <i>c</i> or apparent mean distance. The result is (-2.8 ± 3.4)×10<sup>-12</sup> /yr for either scale rate or -(d<i>c</i>/d<i>t</i>)/<i>c</i>, or equivalently -1.0 ± 1.3 mm/yr for apparent distance rate. The lunar range does not reveal any change in the speed of light.</p>","PeriodicalId":91593,"journal":{"name":"Planetary science","volume":"3 ","pages":"2"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s13535-014-0002-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34359943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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