67P as an apple core

[Enthalpy]

Slightly bizarre idea...

 

67P/Churyumov–Gerasimenko looks like two bodies that assembled loosely. I suggest instead (not even a claim, rather an idea to chew on) that it can have been one sigle, more regular body that has lost more material at what looks now like a neck.

 

This apple core model could for instance have occured as the object's axes had a different orientation. What is now the neck was then the equator and was more or less ecliptic. It received hence more sunheat and sublimated more quickly. After the object got its shape, it tumbled to rotate around the biggest moment of inertia, or flat if you prefer. That's the behaviour of all objects that aren't perfectly stiff; some dissipation process reorients the rotation axis, and maybe deformations of the snow or dust suffices.

 

This could have happened over one orbit around the Sun, with the equator melting when near to the Sun and the axis tumbling when far, or over many orbits, the first ones melting the equator, and the most recent ones tumbling 67P but not having already made it more spherical.

 

Enjoy!

[Enthalpy]

The spinning rate of 67P decreases with time, as reported by the Beeb:

http://www.bbc.com/news/science-environment-31965458

by one second a day from presently 12.4 hour period. This makes a strong change over 100 years spent near the Sun - very quick at astronomical time-scale: the orbital period is 6 years.

 

You can also appreciate visually on Esa's nice picture (click to see the motion, visible on the Bbc's paper too) that 67P has its rotation axis oriented at the biggest moment of inertia:

 

 

This latter supports the idea that damping mechanisms are efficient enough to tumble the rotation axis. Which does not imply that the neck of 67P was previously in the ecliptic plane hence evaporated more quickly - but that a necessary condition, the ability to tumble, is met.

Edited March 21, 2015 by Enthalpy

[Enthalpy]

Investigators of the Osiris camera team on Rosetta tell now that their observations favour the formation of Rosetta by the contact of two bodies rather than the erosion of a singe one.

http://www.bbc.com/news/science-environment-34379287

 

One argument is that the duck's body and head show strata that are independent from an other.

 

An other argument results from the observed gravity field.