Tuesday, November 10, 2015

Monoliths matching their initial seating points

Boulder type objects are ubiquitous on 67P. One well known example is the Cheops boulder on Imhotep. The larger ones (say greater than 10 metre long dimension) I am classing as monoliths just for clarity in this abstract.

The shear line stretch signature helpfully constrains the best areas in which to search for where monoliths may be found to match nearby cliffs which they may have been dislodged from near the fracture zones due to uplift of the head lobe or centrifugal forces.

The best areas are close to the rotation axis at around the North pole (Landing candidate site A, or North Polar plain, or Amphitheatre). This is because any suborbital movement would be constrained by the slower actual velocity of the surface at that point, as the velocity is proportional to the distance to the axis.

The nature of the surface morphology of 67P makes it quite easy to differentiate between features that are part of the surface and those that are monoliths sitting on the surface. Also, the Amphitheatre area has many Navcam images from many angles and resolutions to enable artefacts, foreshortening and whiteout to be adjusted for when considering the detailed shape of the objects in question, both the monolith and the seating position in the cliff. Additionally, the amphitheatre has a very distinctive flat area (stage) and "seating arrangement" fractured slope that makes boulders "stick out" in the same way as they do on the plains of Imhotep.

Following blog posts demonstrate some monoliths with their matches.
Rocks A and B
Rock C
Rock D