Correction: 13 March 2015

www.sciencemag.org/content/347/6220/aaa0440-1/suppl/DC1

Supplementary Materials for

The morphological diversity of comet 67P/Churyumov-Gerasimenko Nicolas Thomas,* Holger Sierks, Cesare Barbieri, Philippe L. Lamy, Rafael Rodrigo, Hans

Rickman, Detlef Koschny, Horst Uwe Keller, Jessica Agarwal, Michael F. A'Hearn, Francesco Angrilli, Anne-Therese Auger, M. Antonella Barucci, Jean-Loup Bertaux, Ivano Bertini, Sebastien Besse, Dennis Bodewits, Gabriele Cremonese, Vania Da Deppo, Björn Davidsson, Mariolino De Cecco, Stefano Debei, Mohamed Ramy El-Maarry, Francesca

Ferri, Sonia Fornasier, Marco Fulle, Lorenza Giacomini, Olivier Groussin, Pedro J. Gutierrez, Carsten Güttler, Stubbe F. Hviid, Wing-Huen Ip, Laurent Jorda, Jörg

Knollenberg, J.-Rainer Kramm, Ekkehard Kührt, Michael Küppers, Fiorangela La Forgia, Luisa M. Lara, Monica Lazzarin, Josè J. Lopez Moreno, Sara Magrin, Simone Marchi,

Francesco Marzari, Matteo Massironi, Harald Michalik, Richard Moissl, Stefano Mottola, Giampiero Naletto, Nilda Oklay, Maurizio Pajola, Antoine Pommerol, Frank Preusker, Lola Sabau, Frank Scholten, Colin Snodgrass, Cecilia Tubiana, Jean-Baptiste Vincent,

Klaus-Peter Wenzel

*Corresponding author. E-mail: nicolas.thomas@space.unibe.ch

Published 23 January 2015, Science 347, aaa0440-1 (2015) DOI: 10.1126/science.aaa0440

This PDF file includes:

Figs. S1 to S11 Table S1

Correction: Fig. S1 has been updated to reflect the most recent coordinate system definition, consistent with Sierks et al. (Science, this issue).

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Supplementary Materials for

The morphological diversity of comet 67P/Churyumov-Gerasimenko

Nicolas Thomas, Holger Sierks, Cesare Barbieri, Philippe L. Lamy, Rafael Rodrigo,

Hans Rickman, Detlef Koschny, Horst Uwe Keller, Jessica Agarwal, Michael F. A'Hearn, Francesco Angrilli, Anne-Therese Auger, M. Antonella Barucci, Jean-Loup Bertaux,

Ivano Bertini, Sebastien Besse, Dennis Bodewits, Gabriele Cremonese, Vania Da Deppo, Björn Davidsson, Mariolino De Cecco, Stefano Debei, Mohamed Ramy El-Maarry,

Francesca Ferri, Sonia Fornasier, Marco Fulle, Lorenza Giacomini, Olivier Groussin, Pedro J. Gutierrez, Carsten Güttler, Stubbe F. Hviid, Wing-Huen Ip, Laurent Jorda, Jörg

Knollenberg, J.-Rainer Kramm, Ekkehard Kührt, Michael Küppers, Fiorangela La Forgia, Luisa M. Lara, Monica Lazzarin, Josè J. Lopez Moreno, Sara Magrin, Simone Marchi,

Francesco Marzari, Matteo Massironi, Harald Michalik, Richard Moissl, Stefano Mottola, Giampiero Naletto, Nilda Oklay, Maurizio Pajola, Antoine Pommerol, Frank Preusker, Lola Sabau, Frank Scholten, Colin Snodgrass, Cecilia Tubiana, Jean-Baptiste Vincent,

Klaus-Peter Wenzel. correspondence to: nicolas.thomas@space.unibe.ch

In this SOM, we provide supporting images for the statements made in the main text (Figs. S1-S11). In addition, we present a table which briefly explains the regional definitions used in the paper (Table S1). In Fig. S1, we show the current shape model of the nucleus with the derived rotation axis. Taken from this model, the largest dimension (diameter) in the equatorial xy-plane is about 5.1 km and the width in the north polar (+z) direction is about 1.6 km. The width in the southern (-z) direction will be refined as the object approaches perihelion. For 67P’s surface on the northern hemisphere, the radial distances from the current nominal centre of mass vary by almost a factor of 6, from ~0.47 km in the neck region to ~2.63 km on both the head and the body. Note: This figure was changed on 13 February 2015 to use a new coordinate system for the comet following a definition similar to that used by ESA. This coordinate system change was implemented in the companion paper by Sierks et al. and has been updated here for consistency with that paper.

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Fig. S1 Nucleus shape model based upon the SPG technique.

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In Fig. S2, we show an impact crater candidate. This crater appears to have been partially buried and we infer that low velocity airfall from nearby activity is responsible. From depth/diameter considerations and standard scaling laws we infer the depth of the deposit.

Fig. S2 Image of the impact crater candidate. The crater is around 35 m in diameter. Estimated depth/diameter ratios lead to an estimated deposit depth of 1-5 m (NAC_2014-09-10T18.34.00.345Z_ID10_1397549000_F22).

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In Figs. S3 and S4, we presented evidence for Aeolian transport across the surface in the form of dunes (Fig. S3), Aeolian ripples (Fig. S4, left) and wind tails (Fig. S4, right).

Fig. S3 Possible dune structures in dust on the nucleus surface. (NAC_2014-08-23T12.42.54.577Z_ID30_1397549700_F22)

Fig. S4 (left) Aeolian ripples in the Hapi region (NAC_2014-09-18T00.33.01.377Z_ID10_1397549800_F22). (right) Wind tails behind rocks in the Hapi region.

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In Fig. S5, we show a wide-angle camera observation of the nucleus. This view illustrates the morphological difference between the Anuket region (marked A) and the Ma’at region (marked B) and shows the scarp which separates the two regions. This orientation also shows how the alcove discussed in the main text appears to “eat into” the head of the nucleus. The evidence of activity and mass loss in the alcove supports the conclusion that we are seeing the interior of the head of the nucleus in this region. The Hathor region with its organized lineaments (in shadow here and marked D) is adjacent to the alcove and almost perpendicular to the smooth Hapi region (marked C) which was the source of earliest dust activity. Fig. S6 shows the alcove from above. The bright spots in the surface of the consolidated material may be volatile-rich and an indicator that the consolidated material may also be actively outgassing and therefore eroding.

Fig. S5 WAC view of the Ma'at/Anuket boundary on the head of the nucleus which shows the steep scarp between the two regions (WAC_2014-09-12T15.09.59.414Z_ID10_1397549500_F17) Arrow A points at Anuket, B at Ma’at, C at the Hapi region, and D at the Hathor region. Arrow E points at the eroding alcove seen illuminated in Figure 5 left and Figure S6.

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In Fig. S6, the bright alcove of Figure 5 left is seen from a different orientation. The bright patches seen in the consolidated material are seen at all observing geometries whereas adjacent surfaces do not show similar photometric behavior.

Fig. S6 The bright alcove of Figure 5 left seen from a different orientation (essentially from above). Note the bright materials in the consolidated material indicated by the arrows. Note also that there is no evidence of this type of bright material in adjacent consolidated material under almost identical illumination conditions. (NAC_2014-08-07T19.20.34.558Z_ID30_1397549100_F22)

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In Fig. S7, we see the quasi-linear cracks in Anuket which extend from Hapi around the neck. The lineament set is around 500 m long. It is tempting to suggest that this is indicative of stresses at the head-body interface which might ultimately lead to nucleus splitting. However, the depth and production mechanism of this structure is unknown. A computation of the torques at the neck produced by heterogeneous outgassing at perihelion is warranted.

Fig. S7 Long (500 m) crack in the surface of the nucleus in the Anuket region (NAC_2014-08-16T10.59.16.348Z_ID30_1397549700_F22).

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In Fig. S8, a block of material to the right has a similar shape and appearance to the depression on the left. The block is around 100 m in diameter. This may be evidence of surface disruption and material ejection produced by sub-surface gas pressure build-up of a super-volatile such as CO or CO2. This concept could explain several observed structures on the nucleus. However, the proposal needs to overcome the high porosity of the nucleus and explain how gas can be trapped in a pocket so that pressure can build. Mechanisms producing sub-surface ice barriers (through volatile transport to colder areas within the nucleus) need to be considered.

Fig. S8 Maftet blocks. On the left (position A) there is a 150 m diameter pit. To the right (position B) is a similar sized block sitting on the surface. (NAC_2014-09-19T00.40.54.603Z_ID10_1397549700_F22)

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In Fig. S9, we see evidence of a flow in the Maftet region. This supports the concept of sub-surface fluidization mechanisms.

Fig. S9 A pit in the Maftet region with associated smooth material which might be related to fluidized outflow from the sub-surface. (NAC_2014-09-19T00.40.54.603Z_ID10_1397549700_F22.IMG)

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The centre of the Imhotep region is extremely smooth and gives the impression of a flow. In Fig. S10, we show that the emplacement mechanism must have been more complex. The smooth material is seen on different topographic levels and it is not draped across these levels. Furthermore, smooth material appears to extend into the rougher Khepry region.

Fig. S10 The boundary of the Imhotep region with Khepry. Imhotep is to the right; Khepry to the left. The smooth material which dominates the centre of Imhotep is seen on different topography levels. Note the step at position (A). There is a depression partially filled with smooth material (B). Smooth material is also seen at positions (C), (D), and (E).

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In Fig. S11, we show Fig. 1 again, but this time with a mark-up of the position on the nucleus of each figure in the paper. This is intended to help place the shown figures in context.

Fig. S11 Figure 1 of the main text but with the positions of the individual high resolution figures in the rest of the text marked. (Sx = supplementary material figure; xL or xR = main text figure left or right).

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Table S1.

S1 - Regional description

Basic description and morphology of the various regions that are described in the main text. The regions on comet 67P/Churyumov-Gerasimenko are given names of ancient Egyptian deities. The regions on the “head” part are given female names whereas the regions on the “body” and “neck” are assigned male names. The boundaries of the different regions were defined at sharp changes in surface morphology (e.g., rough vs smooth surface) or clear structural/ topographical boundaries (e.g., ridge or edge of a depression). Please refer to the figures in the main text for a visual representation of the extent and boundaries of the different regions. It should be noted that within regions there is additional smaller scale morphological diversity which will require detailed mapping in future. The regions can be grouped into the following basic categories dust-covered terrains (A); brittle materials producing fine fragments with pits and circular structures (B); large-scale depressions (C); smooth terrains (D); exposed consolidated surfaces (E) although this categorization is crude and differences exist within each category. Region  Category   

Description 

Head

Hatmehit  C  Well‐defined depression in the head region that appears to be filled with fine‐grained smooth material overlain by a talus. We use the topography of the edge of the depression to define the region. 

Ma’at  A  Main dust‐covered region on the head. Similar to Ash. Smooth deposits showing ripple‐like structures, a possible sign of mobilization. Sharp outcrops of underlying material are usually observed. 

Maftet  E  Rough terrain, lineated, and bouldered with scattered patches of debris neighboring the Hatmehit, Nut and Serqet regions. Many small irregular depressions and pits which give the appearance of lifted blocks/chunks of material and possible fluidized volatile activity. 

Bastet  E  Rough and heavily lineated region with minimal bouldering. Possibly part of the basal unit. Borders Hathor and requires anaglyph of the region to identify topographic differences. Separated from Ma’at by showing only limited debris cover. 

Nut  C  Small depression between the Serqet ridge and the Ma’at/Hatmehit region. Heavily bouldered. Possible result of erosion of Serqet. Identifiable mostly through topography. 

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Serqet  E  Small region encompassing a sharp ridge and a flat and smooth plain with few boulders. The Serqet/Ma’at boundary is gradual. The Serqet/Anuket boundary is clearly defined by topography. The Serqet/Nut boundary is where the plain finishes and the surface texture changes from smooth to bouldered.   

Hathor  E  A complex region opposite the Seth region on the body and hanging over the Hapi region. Un‐mantled and heavily lineated in two dimensions. Shows signs of detachment. Lighting makes the lineated appearance appear very uniform but other viewing angles show that it is rough. 

Anuket   E  A complex unit that is separated from Hathor by a ridge.  Parallel lineations evident on Hathor are limited to absent. It is separated from Ma’at and Serqet by topography being somewhat depressed with respect to these. 

Neck 

Hapi  D  Narrow region connecting the head and body of the comet. Currently the most active region and site of regular jet activity although exact source not defined. Smooth dusty‐looking material along with dispersed large boulders that may have slumped from the head or body regions. 

Body 

Imhotep  D  Geologically the most complex region on C‐G. Extremely smooth, probably recently re‐surfaced, yet bouldered region enclosed by horizontally bedded and vertically jointed ridges. There is strong evidence of mass‐wasting all around the smooth areas as well as the presence of conical structures and pits that are possibly the result of fluidization mechanisms. 

Ash  A  Main dust‐covered region of the body. Smooth deposits possibly a few meters thick. Similar to Ma’at region. Contains the only currently unambiguously identified impact crater on the surface of the comet. 

Khepry  E  Rough‐ and bright‐looking unit neighboring the Imhotep, Aten and Aker regions. Moderately lineated. Possibly an exposure of the comet’s basal unit.  Rough by comparison with Aker although transition to it is gradual. 

Aten  C  Well‐defined depression between the Imhotep, Ash and Khepry regions. Not covered by airfall with no mantling material and hence clearly separable from Ash. 

Aker  E  Dark‐toned unit with a mixed degree of roughness. Lineated and showing tectonic‐like features. Possibly a reworked section of the Khepry region. Several small smooth areas 

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(ponded dust) evident. 

Babi  A  Transitional region that grades smoothly into Ash and Seth regions in terms of debris cover. Neighbors the Aten and Aker regions and displays exposures of brittle mantling material at its contact with the Aten depression. 

Atum  E  Highly complex region. Minimal bouldering but several small depressions showing some lineation. Irregular complex mounds also seen. Borders the Anubis unit with ill‐defined margins in places. 

Anubis  D  Smooth region very similar to Imhotep and, possibly, Hapi. Some scattered boulders possibly a result of mass‐wasting. Smooth deposits appear faulted/folded in some places and display linear features similar to those observed in Imhotep. Cones seen in Imhotep are absent. 

Apis  E  Flat, smooth, and lineated unit showing irregular and polygonal lineations. Significant topographic change with respect to Atum and Imhotep. 

Seth  B  Ubiquitous circular, semi‐circular, and quasi‐circular features. Strong evidence of collapse with active pits. Sharp topographic  contact with Anubis. May underlie Hapi. 

Table S1 Basic description and morphology of the various regions that are described in the main text.