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

Original Submission submitted to A&A Feb. 4 2016

Triggered by OSIRIS Observations

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

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 (http://imagearchives.esac.esa.int), with identification numbers N20140808T062034578ID30F22 (a) and N20140826T074254573ID30F22 (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.

A&A accepted

Not in the Manuscript

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

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?

Temperature inside Nucleus

Temperature inside Nucleus

Temperature as a function of cometary depth for the orbital position corresponding to early August, 2015. 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.

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).

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.

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