Edge detection applied to Cassini images reveals no measurable displacement of Ontario Lacus' margin between 2005 and 2010

Research areas:

• Environnement, Paléo-Environnement et Bio-Indicateurs (2011 - 2016)

Year:

2012

Authors:

• Thomas Cornet
• Olivier Bourgeois
• Stéphane Le Mouélic
• Sebastien Rodriguez
• Christophe Sotin
• Jason W. Barnes
• Robert H. Brown
• Kevin H. Baines
• Bonnie J. Buratti
• Roger N. Clark
• Phillip D. Nicholson

Journal:

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS

Volume:

117

Month:

JUL 18

ISSN:

0148-0227

BibTex:

@article{WOS:000306700500002, author = "Thomas Cornet and Olivier Bourgeois and St{\'e}phane Le Mou{\'e}lic and Sebastien Rodriguez and Christophe Sotin and Jason W. Barnes and Robert H. Brown and Kevin H. Baines and Bonnie J. Buratti and Roger N. Clark and Phillip D. Nicholson", abstract = "Ontario Lacus is thus far the largest flat-floored topographic depression of Titan{\&}#039;s southern hemisphere interpreted as a permanent or ephemeral lake. From 2005 to 2010, it was imaged several times and at various wavelengths by ISS, VIMS and RADAR instruments onboard Cassini{\&}#039;s spacecraft. We analyze the position and uncertainty of Ontario Lacus{\&}#039; margin in all these images using an edge detection method based on image derivation. We find that, given the range of uncertainties in contour locations derived from images, no measurable displacement of Ontario Lacus{\&}#039; margin can be detected between 2005 and 2010 at the actual image spatial resolutions. The discrepancy between this result and previous ones is attributable to differences in (1) the basics behind the methods used, (2) the actual spatial resolutions and contrasts of the available images due to differential atmospheric scattering effects at different wavelengths, and (3) the geomorphological interpretation of contours derived from images acquired at different wavelengths. This lack of measurable displacement in the images suggests that the imaged contour corresponds either (1) to the border of a surface liquid body, provided that potential changes in its extent over five terrestrial years were not sufficiently large to be measured, or (2) to the stationary topographic border between Ontario Lacus{\&}#039; depression and the surrounding alluvial plain. Potential displacements of Ontario Lacus{\&}#039; margin between 2005 and 2010 are thus below the actual resolution of currently available images or have to be sought for within the extent of the topographic depression rather than along its borders.", doi = "10.1029/2012JE004073", extra = "PICL", issn = "0148-0227", journal = "JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS", month = "JUL 18", title = "{E}dge detection applied to {C}assini images reveals no measurable displacement of {O}ntario {L}acus{\&}#039; margin between 2005 and 2010", volume = "117", year = "2012", }

Abstract:

Ontario Lacus is thus far the largest flat-floored topographic
depression of Titan's southern hemisphere interpreted as a permanent or
ephemeral lake. From 2005 to 2010, it was imaged several times and at
various wavelengths by ISS, VIMS and RADAR instruments onboard Cassini's
spacecraft. We analyze the position and uncertainty of Ontario Lacus'
margin in all these images using an edge detection method based on image
derivation. We find that, given the range of uncertainties in contour
locations derived from images, no measurable displacement of Ontario
Lacus' margin can be detected between 2005 and 2010 at the actual image
spatial resolutions. The discrepancy between this result and previous
ones is attributable to differences in (1) the basics behind the methods
used, (2) the actual spatial resolutions and contrasts of the available
images due to differential atmospheric scattering effects at different
wavelengths, and (3) the geomorphological interpretation of contours
derived from images acquired at different wavelengths. This lack of
measurable displacement in the images suggests that the imaged contour
corresponds either (1) to the border of a surface liquid body, provided
that potential changes in its extent over five terrestrial years were
not sufficiently large to be measured, or (2) to the stationary
topographic border between Ontario Lacus' depression and the surrounding
alluvial plain. Potential displacements of Ontario Lacus' margin between
2005 and 2010 are thus below the actual resolution of currently
available images or have to be sought for within the extent of the
topographic depression rather than along its borders.