1. Outbursts from fractures
H. Uwe Keller1,2 and Yuri Skorov3
1 IGEP Universität Braunschweig
2 DLR Planetenforschung
3 MPS

2. Original Submission
submitted to A&A Feb

3. Triggered by OSIRIS Observations

4. Distribution and Suppression
Referee/editor of A&A questioned the use of the illustrative PR images published on the ESA web site
Rosetta PIs were consulted by the A&A editor
Skorov’s manuscript was distributed within the OSIRIS lead scientists group!
The distribution of a just submitted manuscript propagating a new idea within the science community is scandalous
I am appalled by the OSIRIS “leadership” reaction. Is this in the interest of OSIRIS?
Skorov was forced to resubmit w/o reference to OSIRIS

5. What about this publication?
Two straight cracks, viewed from different angles, in the Hapi region9. Data are available at the European Space Agency (ESA) image browser ( with identification numbers N T ID30F22 (a) and N T ID30F22 (b). Image credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; original images processed by ESA/Rosetta/SGS/PSA&ESDC to create image for Archive Imager Browser.

6. A&A accepted

7. Not in the Manuscript

9. Geological View Comparison to tension fractures as found on earth
How deep are the fractures in Anuket?
Fracture depth comparable to fracture spacing =>
Depth of Anuket fractures about 15 to 70 m
Alternate approach: Griffith criterion:
for σT = 3 to 15 Pa this yields depth between 100 – 500 m
Fractures reach down into the “pristine” nucleus

10. Model The following key issues are addressed in our modeling:
– Can super-volatiles exist as ice at these depths (50 to 100 m)? – Can the sudden dis-equilibration of the region which is rich in the super-volatiles produce reasonable amounts of dust and gas? – Can this activity be stopped after a short time?

11. Temperature inside Nucleus

12. Temperature inside Nucleus

13. Temperature as a function of cometary depth for the orbital position corresponding to early August, A slow rotator model is applied for the case Model C accounting for a surface erosion. The depth is measured from the surface position after ten orbital periods (showing result for the 5–10 orbit). The primordial temperature is fixed at 30 K and the thermal inertia is set to 30 J m−2 K−1 s0.5 (upper value from MIRO analysis.

14. Diffusivity is negligible for mm pores
0.5 g of CO per 1 m3 in equilibrium with CO ice (~ 5 kg) at T = 40 K
Diffusivity is negligible for mm pores
CO saturation vapor pressure (left y-axis scale, solid line) as a function of temperature. The corresponding mass loss rate is shown on the right–hand y-axis scale (dashed line).

15. Additional sublimation liberates 104 times more CO
Additional sublimation liberates 104 times more CO. A few m2 are needed to release 1 kg CO. Cooling quenches sublimation.

17. Summary
Attractive new features of the model that explains short outbursts:
– independence of external heat flux induced by solar irradiation
– natural self-induced quenching of the outburst activity after a short time – In addition, the model does not require presence of large isolated cavities in the nucleus – and/or crystallization of amorphous ice and trapped super volatiles release