Part 74- Temporal Morphological Changes in the Hapi/Ripples Region of 67P/Churyumov-Gerasimenko Cast Doubt on Aeolian Dune Theory

The photo below is the original for the above. This is a control photo used to show the area before the near-perihelion changes took place. It’s from Thomas et al. 2015 and was taken well before perihelion. The annotations therefore show future changes in this area.

Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER 
All photos below have this credit as well.

The header photos show  one particular stage in the progress of the morphological changes in the Hapi region that occurred between 15th April 2015 and 27th February 2016. 
The morphological changes proceeded in a manner that was in keeping with the changes that commenced at Imhotep some six weeks later and lasted for at least six more weeks. The Imhotep changes were documented in Groussin et al. 2015. 
The changes continued before and after the April 25th photo above. Below is a longer, 21-photo chronology. More commentary will be posted later. 

The January 17th 2016 photo was used in Jia et al. 2017. That paper argued that the vestigial scarp-like features are dunes. The largest supposed dune is in fact the final resting place of the large scarp in the April 25th photo above. It is not a dune. 
The dune theory will now have to argue that two successive pits of ~5m depth appearing in the middle of the ripples and eroding across them can be reconciled with gentle transverse winds propagating the supposed dunes ten metres in the opposite direction to the erosion and at the same time. 

THE 21-PHOTO CHRONOLOGY

Photos have annotations as follows:

Red- fiduciary points. They’re the two ends of the cliff that the ripples kiss. They’re almost exactly 100m apart. 

Light blue- fiduciary points. These are four recognisable boulders that  enclose the area of most interest. But look for major subsidence of the same nature in the adjoining area too. That area is always shown. Its very obvious dips appear and grow just like in the ripples area. This suggests subsidence/erosion is the driving mechanism over this entire area, not aeolian dune migration. 
Text annotations:

The date of the photo.

‘+[a number]’: days since last photo in the sequence. This helps understand the changes/rate of propagation.

MTP number/Photo number.

28th March shows first definitive changes. There were possible smaller changes from March 15th (not included here).


PHOTO CREDITS
FOR OSIRIS:
Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER

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