Vol 453 LETTERS - UC Santa Cruzfnimmo/website/circles.pdf · LETTERS True polar wander on Europa...
4
LETTERS True polar wander on Europa from global-scale small-circle depressions Paul Schenk 1 , Isamu Matsuyama 2 & Francis Nimmo 3 The tectonic patterns and stress history of Europa are exceedingly complex 1 and many large-scale features remain unexplained. True polar wander, involving reorientation of Europa’s floating outer ice shell about the tidal axis with Jupiter, has been proposed 2 as a possible explanation for some of the features. This mechanism is possible if the icy shell is latitudinally variable in thickness and decoupled from the rocky interior. It would impose high stress levels on the shell, leading to predictable fracture patterns 3 . No satisfactory match to global-scale features has hitherto been found for polar wander stress patterns 3 . Here we describe broad arcuate troughs and depressions on Europa that do not fit other proposed stress mechanisms in their current position. Using imaging from three spacecraft, we have mapped two global-scale organized con- centric antipodal sets of arcuate troughs up to hundreds of kilo- metres long and 300 m to 1.5 km deep. An excellent match to these features is found with stresses caused by an episode of 806 true polar wander. These depressions also appear to be geo- graphically related to other large-scale bright and dark linea- ments 4,5 , suggesting that many of Europa’s tectonic patterns may also be related to true polar wander. Three arcuate troughs 25–40 km across and $500 km long have been identified on Europa from imaging data obtained with Voyager, Galileo and New Horizons spacecraft (Figs 1, 2). Although no bound- ing walls, scarps or geologic discontinuities can be resolved in Galileo images, the observed topographic subsidence suggests that extension has occurred. Two troughs are observed on the leading hemisphere, forming opposing quadrants of a large, essentially perfectly circular, feature 2,350 km in diameter (Fig. 2). Together, these arcs, referred to as circle L, have a least-squares best-fit centre 6 of 10u S, 120u 6 1u W and spherical radius of 43.3u. Circle L is of a type known as a ‘small circle’, as its plane does not go through the centre of Europa. Neither trough deviates more than 0.3u from circularity (Supplementary Fig. 1). The circle is symmetric but incomplete; troughs are absent in the northwest and southeast sectors, despite suitable imaging (Figs 1, 2), and apparently did not form. Only one arcuate trough segment was observed on the trailing hemisphere (Figs 1c, 2). This trough has a best-fit centre of 10u N, 300u W, antipodal to circle L and forming part of a second circular trough feature, circle T. By symmetry with circle L, we expect another segment near 270u W, but neither Voyager nor Galileo acquired low-Sun imaging in this region (Fig. 2). No trough has as yet been identified in New Horizons 7 imaging of this region, owing to the morphologic complexity of the region and low image resolution (,17 km per pixel). Several shorter arcuate closed depressions 100–200 km long also occur parallel to, and in close association with, the long arcuate troughs (Figs 1, 2). These occur 48u to 52u from the respective best-fit centres in widely dispersed positions 100 to 300 km exterior to the larger arcuate troughs. Two morphologies occur (Fig. 1): sets of two to three parallel short linear troughs ,100 km apart, and isolated elongate bulbous-shaped steep-walled depressions (Fig. 3). Limited stereo and photoclinometric topography (Supplementary Information) indicate relief across arcuate troughs of 300 6 50 m, but relief across secondary basins is found to be 900–1,500 m. The latter are the deepest features known on Europa, with relief compar- able to elevated plateaus elsewhere 8–10 , indicating a total dynamic range of relief on Europa of nearly 2 km. Despite their depths and pervasive deformation across most of Europa 11 , there are no indica- tions of disruption, deformation or lateral displacement of pre- existing features across the floors of these depressions, nor are there indications of emplacement of new material on these depression floors (Fig. 3). Ridges and chaos on Europa either pre-date these depressions, or formed unaffected by their presence. The observed troughs and secondary basins (Fig. 2) form two well- defined and antipodal sets of concentric small-circle depressions (SCDs) 12 , offset 10u from the equator and 30u from the present tidal axis (oriented towards Jupiter). SCD geography appears correlated with several major geologic features on Europa. A great circle oriented ,50u to the equator through the best-fit centres (Fig. 4) approximately bisects all three observed trough segments, and passes near and parallel to two unusual bright bands on Europa, Agenor Linea 4,5 and Corick Linea 13 . Both bands are also antipodal to each other and lie midway between each circle. This symmetry is unlikely to be mere coincidence. On either side of Agenor Linea (and the great circle) lie two zones of orthogonal strike-slip and pull-apart faulting associated with dark wedge-shaped bands 5 ; this faulting involves formation of .100 km of new lithospheric material. Stratigraphically, Agenor Linea and the pull-apart bands are inter- mediate to young in age 1,11 . If SCDs, pull-apart bands and bright bands are related, then the SCDs might also date from this period. The global nature and symmetry of the SCDs suggests that global stresses are involved, most probably those due to global expansion/ contraction 14 , tidal flexing 15 , despinning 16 and/or reorientation. Reorientation can include non-synchronous rotation 17 about the polar axis, and true polar wander 2 (TPW), involving rotation of the polar regions to the equator. Expansion/contraction gives rise to isotropic stress patterns 14 . The orientations of large-scale linea- ments on Europa, specifically cycloid ridges and triple bands, are consistent with diurnal stresses 18 and ordinary non-synchronous rotation 15,16,19 , respectively, although we note that these global stress patterns (as well as despinning stresses) are symmetric about the equator, unlike our features. Accordingly, we consider that stresses due to reorientation of the surface relative to the principal axes 2,17 are the most likely cause of the circles. Reorientations due to TPW and to non-synchronous rotation are both dynamically possible on Europa 2,17 . Non-synchronous rotation 1 Lunar and Planetary Institute, Houston, Texas 77058, USA. 2 Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA. 3 Department of Earth & Planetary Sciences, University of California, Santa Cruz, California 95064, USA. Vol 453 | 15 May 2008 | doi:10.1038/nature06911 368 Nature Publishing Group ©2008
Transcript of Vol 453 LETTERS - UC Santa Cruzfnimmo/website/circles.pdf · LETTERS True polar wander on Europa...
LETTERS
True polar wander on Europa from global-scalesmall-circle depressionsPaul Schenk1, Isamu Matsuyama2 & Francis Nimmo3
The tectonic patterns and stress history of Europa are exceedinglycomplex1 and many large-scale features remain unexplained. Truepolar wander, involving reorientation of Europa’s floating outerice shell about the tidal axis with Jupiter, has been proposed2 as apossible explanation for some of the features. This mechanism ispossible if the icy shell is latitudinally variable in thickness anddecoupled from the rocky interior. It would impose high stresslevels on the shell, leading to predictable fracture patterns3. Nosatisfactory match to global-scale features has hitherto been foundfor polar wander stress patterns3. Here we describe broad arcuatetroughs and depressions on Europa that do not fit other proposedstress mechanisms in their current position. Using imaging fromthree spacecraft, we have mapped two global-scale organized con-centric antipodal sets of arcuate troughs up to hundreds of kilo-metres long and 300 m to 1.5 km deep. An excellent match tothese features is found with stresses caused by an episode of
806 true polar wander. These depressions also appear to be geo-graphically related to other large-scale bright and dark linea-ments4,5, suggesting that many of Europa’s tectonic patterns mayalso be related to true polar wander.
Three arcuate troughs 25–40 km across and $500 km long havebeen identified on Europa from imaging data obtained with Voyager,Galileo and New Horizons spacecraft (Figs 1, 2). Although no bound-ing walls, scarps or geologic discontinuities can be resolved in Galileoimages, the observed topographic subsidence suggests that extensionhas occurred. Two troughs are observed on the leading hemisphere,forming opposing quadrants of a large, essentially perfectly circular,feature 2,350 km in diameter (Fig. 2). Together, these arcs, referred toas circle L, have a least-squares best-fit centre6 of 10u S, 120u6 1uWand spherical radius of 43.3u. Circle L is of a type known as a ‘smallcircle’, as its plane does not go through the centre of Europa. Neithertrough deviates more than 0.3u from circularity (Supplementary Fig.1). The circle is symmetric but incomplete; troughs are absent in thenorthwest and southeast sectors, despite suitable imaging (Figs 1, 2),and apparently did not form.
Only one arcuate trough segment was observed on the trailinghemisphere (Figs 1c, 2). This trough has a best-fit centre of 10uN,300uW, antipodal to circle L and forming part of a second circulartrough feature, circle T. By symmetry with circle L, we expect anothersegment near 270uW, but neither Voyager nor Galileo acquiredlow-Sun imaging in this region (Fig. 2). No trough has as yet beenidentified in New Horizons7 imaging of this region, owing to themorphologic complexity of the region and low image resolution(,17 km per pixel).
Several shorter arcuate closed depressions 100–200 km long alsooccur parallel to, and in close association with, the long arcuatetroughs (Figs 1, 2). These occur 48u to 52u from the respectivebest-fit centres in widely dispersed positions 100 to 300 km exterior
to the larger arcuate troughs. Two morphologies occur (Fig. 1): setsof two to three parallel short linear troughs ,100 km apart, andisolated elongate bulbous-shaped steep-walled depressions (Fig. 3).
Limited stereo and photoclinometric topography (SupplementaryInformation) indicate relief across arcuate troughs of 300 6 50 m,but relief across secondary basins is found to be 900–1,500 m. Thelatter are the deepest features known on Europa, with relief compar-able to elevated plateaus elsewhere8–10, indicating a total dynamicrange of relief on Europa of nearly 2 km. Despite their depths andpervasive deformation across most of Europa11, there are no indica-tions of disruption, deformation or lateral displacement of pre-existing features across the floors of these depressions, nor are thereindications of emplacement of new material on these depressionfloors (Fig. 3). Ridges and chaos on Europa either pre-date thesedepressions, or formed unaffected by their presence.
The observed troughs and secondary basins (Fig. 2) form two well-defined and antipodal sets of concentric small-circle depressions(SCDs)12, offset 10u from the equator and 30u from the present tidalaxis (oriented towards Jupiter). SCD geography appears correlatedwith several major geologic features on Europa. A great circleoriented ,50u to the equator through the best-fit centres (Fig. 4)approximately bisects all three observed trough segments, and passesnear and parallel to two unusual bright bands on Europa, AgenorLinea4,5 and Corick Linea13. Both bands are also antipodal to eachother and lie midway between each circle. This symmetry is unlikelyto be mere coincidence. On either side of Agenor Linea (and thegreat circle) lie two zones of orthogonal strike-slip and pull-apartfaulting associated with dark wedge-shaped bands5; this faultinginvolves formation of .100 km of new lithospheric material.Stratigraphically, Agenor Linea and the pull-apart bands are inter-mediate to young in age1,11. If SCDs, pull-apart bands and brightbands are related, then the SCDs might also date from this period.
The global nature and symmetry of the SCDs suggests that globalstresses are involved, most probably those due to global expansion/contraction14, tidal flexing15, despinning16 and/or reorientation.Reorientation can include non-synchronous rotation17 about thepolar axis, and true polar wander2 (TPW), involving rotation ofthe polar regions to the equator. Expansion/contraction gives riseto isotropic stress patterns14. The orientations of large-scale linea-ments on Europa, specifically cycloid ridges and triple bands, areconsistent with diurnal stresses18 and ordinary non-synchronousrotation15,16,19, respectively, although we note that these global stresspatterns (as well as despinning stresses) are symmetric about theequator, unlike our features. Accordingly, we consider that stressesdue to reorientation of the surface relative to the principal axes2,17 arethe most likely cause of the circles.
Reorientations due to TPW and to non-synchronous rotation areboth dynamically possible on Europa2,17. Non-synchronous rotation
1Lunar and Planetary Institute, Houston, Texas 77058, USA. 2Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA. 3Department ofEarth & Planetary Sciences, University of California, Santa Cruz, California 95064, USA.
Vol 453 | 15 May 2008 | doi:10.1038/nature06911
368Nature Publishing Group©2008
generates compressional features centred on the initial tidal axes3,20,which makes the offset location and inferred extensional nature of theSCDs hard to explain. Furthermore, as the SCDs are not centred onor symmetric about the current equator, some TPW must haveoccurred, and TPW results in extensional stresses around the originalrotation axis20,21. Pull-apart bands3 and strike-slip fault and chaosdistributions22 may be related to TPW, but a definitive interpretationhas not been possible because the limited Galileo imaging preventsglobal mapping of these smaller-scale features. Reorientations
approaching 90u have been predicted for Europa2 and are more likelyto occur around the tidal axis23. Stresses developed during TPW aretypically an order of magnitude (or more) larger than diurnal tidalstresses2. Large TPW, with the initial rotation axis passing near themeridians containing the centres of the SCDs, is required to explainthe location of the SCDs.
Figure 4 plots the stress contours and fracture patterns arisingfrom 80u of TPW roughly around the tidal axis, combined with asmall amount (0.002%) of isotropic expansion (Supplementary
a b
c
d
Gap
New Horizons
Galileo
Figure 1 | Regional views of global-scale arcuate troughs and basins onEuropa. a, Southwest quadrant, circle L (L, leading hemisphere: view centredat 25u S, 160uW); b, northeast quadrant, circle L (view centred at 12uN,85uW); c, northwestern quadrant, circle T (T, trailing hemisphere: viewcentred at 27uN, 340uW). Main arcuate troughs (black arrows) andsecondary basins (white arrows) are highlighted. Both types are ,20–50 kmwide but secondary basins are only 100–300 km long. Vertical scale bars are100 km in these cylindrical map projections. d, New Horizons imaging7
(bottom) confirms the northward continuation of the main arcuate trough(arrows) within the Galileo mapping coverage gap (top, and blurry area ofc). North is to top and the Sun is to the west (left) in all images.
90º
60º
30º
0º
0º60º120º180ºLongitude
240º
T
L
300º360º
Latit
ude
–30º
–60º
–90º
Figure 2 | A global map of the distribution of large-scale arcuate troughsand basins on Europa. Black curves, locations of arcuate troughs andsecondary basins. Low-Sun regional Voyager and Galileo imaging of the typerequired to observe these features (white regions) covers approximately20–30% of the surface in widely dispersed north–south longitudinal bands at220–1,500 m per pixel resolution. New Horizons7 acquired imaging at17–20 km resolution between longitudes 270u and 360uW, showing anorthern extension of the trough segment at 340u longitude into theVoyager-Galileo data gap. Dots are least-squares centres of curvature forcircle L (L) and circle T (T). Dashed curve at 270uW is the predicted locationof the eastern arcuate trough segment of circle T, unobserved by Galileo andnot detected by New Horizons. Longitude is in degrees west; positive andnegative latitude denotes degrees north and south, respectively.
25 km
d
Figure 3 | Highest-resolution image mosaic of a large secondary basin onEuropa. Shown is a high resolution (230 m per pixel) Galileo image mosaicof the southern part of a large secondary basin (d) in the southwest quadrantof circle L. Low-resolution data in the upper section is global context imagingat 1.5 km per pixel. Continuity of ridges and dark features across the marginof the basin and a lack of unusual resurfacing on its floor are evident. Scene isan enlargement of the centre left portion of Fig. 1a. Image resolution (230 mper pixel) is not sufficient to resolve the nature of the steep margins, whichmost probably are due to unresolved normal faults or to monoclinal folding.
NATURE | Vol 453 | 15 May 2008 LETTERS
369Nature Publishing Group©2008
Information). We arrived at a solution with the palaeopole at 10uN,280uW, and a self-consistent reorientation of the tidal axis such thatthe initial sub-Jupiter point (0u, 0uW) is now at 10u S, 8.2uW.Although there are similar solutions that can match the size andlocation of the SCDs, all of them involve a large TPW and a small,self-consistent reorientation of the tidal axis. We chose the solutionwith the palaeopole at 10uN, 280uW because, in addition to match-ing the location and size of the SCDs, the deviatoric stress ismaximum where depressed segments of the circles are observed. Ifthe arcuate troughs are extensional, then they are likely to form firstwithin the regions dominated by extensional faulting where themaximum extensional stresses occur. The locations and orientationsof the SCDs follow this prediction very closely (Fig. 4). If Agenor andCorick Lineae are strike-slip duplex features4, their locations (andperhaps their orientations) are also consistent with the predictedstresses, as are the locations and orientations of the orthogonalpull-apart bands (Fig. 4b).
Assuming that the secondary basins are fault-bounded, amaximum depth of 1 km implies a total extension of ,2 km, or aglobal strain of ,0.02%. An isostatically supported trough 1 km deepwould imply a minimum shell thickness of 6–17 km (ref. 8), depend-ing on shell and ocean composition, although short shell-flow time-scales24 suggest that flexural support may be a more likelymechanism.
The SCDs form a striking set of features unique to Europa. An,80u reorientation event involving TPW explains the observedlocations, orientations and characteristics of the SCDs. Large-scalelineaments such as pull-apart bands, bright bands, as well as triplebands (currently thought to have formed during ordinary non-synchronous rotation19), form a symmetric pattern with respect toTPW stress patterns, and can also potentially be explained as exten-sional or strike-slip features formed during this TPW episode. Thesecorrelations suggest that the origins of many of Europa’s tectonic anddiapiric features1,11 should be re-evaluated to determine whether theyalso formed, or were displaced22, during the reorientation proposedhere. This can partly be accomplished with Galileo’s severely limitedmapping coverage, but will ultimately require a new high-resolutionglobal mapping mission to Europa.
Polar reorientation by ,70–90u is an expected consequence oflatitudinally varying thickness in a decoupled ice shell on Europa2,3,although dissipation within the ice shell is likely to reduce thisreorientation somewhat25. TPW on Europa also provides an inde-pendent line of evidence that the ice shell is (or once was) floatingon a sub-surface water ocean2. Our hypothesized episode ofTPW places Europa in the company of Mars26,27, Enceladus28 andperhaps Miranda29, and may have fundamentally reshapedEuropa’s geology.
Received 18 July 2007; accepted 6 March 2008.
1. Greeley, R. et al. in Jupiter (eds Bagenal, F., Dowling, T. & McKinnon, W.) 329–362(Cambridge Univ. Press, Cambridge, UK, 2004).
2. Ojakangas, G. & Stevenson, D. Polar wander of an ice shell on Europa. Icarus 81,242–270 (1989).
3. Leith, A. & McKinnon, W. Is there evidence for polar wander on Europa? Icarus120, 387–398 (1996).
4. Prockter, L., Pappalardo, R. & Head, J. Strike-slip duplexing on Jupiter’s icy moonEuropa. J. Geophys. Res. 105, 9483–9488 (2000).
5. Schenk, P. & McKinnon, W. Fault offsets and lateral crustal movement on Europa:Evidence for a mobile ice shell. Icarus 79, 75–100 (1989).
6. Schenk, P. & McKinnon, W. Ring geometry on Ganymede and Callisto. Icarus 72,209–234 (1987).
7. Grundy, W. et al. New Horizons mapping of Europa and Ganymede. Science 318,234–238 (2007).
8. Schenk, P. & McKinnon, W. Topographic variability on Europa from Galileo stereoimages. Lunar Planet. Sci. Conf. 32, abstr. 2078 (2001).
9. Figueredo, P. & Greeley, R. Geologic mapping of the northern leading hemisphereof Europa from Galileo solid-state imaging data. J. Geophys. Res. 105,22629–22646 (2000).
10. Prockter, L. & Schenk, P. Origin and evolution of Castalia Macula, an anomalousyoung depression on Europa. Icarus 177, 305–326 (2005).
11. Figueredo, P. & Greeley, R. Resurfacing history of Europa from pole-to-polegeologic mapping. Icarus 167, 287–312 (2004).
12. Schenk, P. Crop circles of Europa. Lunar Planet. Sci. Conf. 30, abstr. 2081(2005).
13. Greenberg, R. The evil twin of Agenor: Tectonic convergence on Europa. Icarus167, 313–319 (2004).
14. Nimmo, F. Stresses generated in cooling viscoelastic ice shells: Application toEuropa. J. Geophys. Res. 109, E12001, doi:10.1029/2004JE002347 (2004).
15. Greenberg, R. et al. Tectonic processes on Europa: Tidal stresses, mechanicalresponse, and visible features. Icarus 135, 64–78 (1998).
16. Melosh, H. J. Global tectonics of a despun planet. Icarus 31, 221–243 (1977).17. Greenberg, R. & Weidenschilling, S. How fast do Galilean satellites spin? Icarus 58,
186–196 (1984).18. Hoppa, G., Tufts, B. R., Greenberg, R. & Geissler, P. Formation of cycloidal features
on Europa. Science 285, 1899–1902 (1999).19. Geissler, P. et al. Evidence for non-synchronous rotation of Europa. Nature 391,
368–370 (1998).20. Matsuyama, I. & Nimmo, F. Tectonic patterns of a reoriented and despun
planetary bodies. Icarus doi:10.1016/j.icarus.2007.12.003 (in the press).
21. Melosh, H. J. Tectonic patterns on a reoriented planet — Mars. Icarus 44, 745–751(1980).
b
a
Figure 4 | Global colour mosaic and predicted stress patterns for true polarwander in a thin elastic shell on Europa. a, Colour mosaic. Blue curves areSCDs, wavy green lines are bright curvilinear bands Agenor Linea(180–240uW longitude) and Corick Linea (0–50uW longitude); red outlinedregions are pull-apart band dilational and strike-slip zones5. A great circle(heavy black curve) roughly bisecting the long arcuate troughs and the twostrike-slip zones is also shown. Long arcuate triple bands lie either side ofthese zones and converge towards the centres of the two circles. b, Stress/fracture map. Palaeopole locations (solid dots: palaeo-north-pole 10uN,280uW) and initial tidal axes (triangles: palaeo-sub-Jupiter-point 10u S,8.2uW) are shown. Total angular reorientation is 80u; isotropic extensionalstrain is 0.002%. The short red lines, grey crosses and blue lines indicatedirections of the expected normal, strike-slip and thrust faulting, respectively.Black lines separate these tectonic regions. Two zones of extensional stress areseparated by 180u and offset in latitude by 20u, separated by regions in whichstrike-slip motions dominate. The centres of the extensional regions are offsetin longitude from the meridians containing the initial rotation axis becausethe reorientation geometry requires a small (8.2u) eastward longitudinalreorientation of the tidal axis such that the rotational and tidal axes remainperpendicular. Pull-apart bands are associated with both dilation and strike-slip faulting oriented northeast–southwest and northwest–southeast5, andAgenor Linea may be a strike-slip zone in combination with extension orcompression4, both consistent with the predicted pattern. Shaded regions andcontours correspond to deviatoric stress in units of MPa. Stresses werecalculated assuming a shear modulus of 9.3 GPa (ref. 22) and Love numberh 5 1. We note that the fit between feature and stress patterns may beenhanced if a further TPW shell rotation of ,15u is assumed.
LETTERS NATURE | Vol 453 | 15 May 2008
370Nature Publishing Group©2008
22. Sarid, M. et al. Polar wander and surface convergence of Europa’s ice shell:Evidence from a survey of strike-slip displacement. Icarus 158, 24–41 (2002).
23. Matsuyama, I. & Nimmo, F. Rotational stability of tidally deformed planetarybodies. J. Geophys. Res. 112, E11003, doi:10.1029/2007JE002942 (2007).
24. Stevenson, D. Limits on the variation of thickness of Europa’s ice shell. LunarPlanet. Sci. Conf. 31, abstr. 1506 (2000).
25. Matsuyama, I., Nimmo, F. & Mitrovica, J. Reorientation of planets withlithospheres: The effect of elastic energy. Icarus 191, 401–412 (2007).
26. Willemann, R. Reorientation of planets with elastic lithospheres. Icarus 60,701–709 (1984).
27. Matsuyama, I., Mitrovica, J., Manga, M., Perron, J. & Richards, M. Rotationalstability of dynamic planets with elastic lithospheres. J. Geophys. Res. 111, E02003,doi:10.1029/2005JE002447 (2006).
28. Nimmo, F. & Pappalardo, R. Diapir-induced reorientation of Saturn’s moonEnceladus. Nature 441, 614–616 (2006).
29. Janes, D. M. & Melosh, H. J. Sinker tectonics — an approach to the surface ofMiranda. J. Geophys. Res. 93, 3127–3143 (1988).
Supplementary Information is linked to the online version of the paper atwww.nature.com/nature.
Acknowledgements This work was supported in part by the NASA Outer PlanetsResearchandPlanetaryGeologyandGeophysicsprogrammes.LPIcontributionno.1399.
Author Contributions Global mapping and topographic analyses were conductedby P.S.; P.S. and F.N. conducted preliminary examination of alternative models;numerical modelling of stress patterns was conducted by I.M.; and P.S wrote thepaper, with contributions from I.M. and F.N.
Author Information Reprints and permissions information is available atwww.nature.com/reprints. Correspondence and requests for materials should beaddressed to P.S. ([email protected]).
NATURE | Vol 453 | 15 May 2008 LETTERS
371Nature Publishing Group©2008
![datos tecnicos - COVASAB] [06] Tapones... · 2020. 12. 23. · 084000 084400 Tapón macho BSP GAS 60º Tapón macho BSPP con junta para llave allen BSP GAS 60º male plug BSPP male](https://static.fdocuments.in/doc/165x107/60e3de08a70c8f6a2f009281/datos-tecnicos-covasa-b-06-tapones-2020-12-23-084000-084400-tapn.jpg)
