PLANETARY SCIENCE

Dunes on PlutoMatt W. Telfer,1*† Eric J. R. Parteli,2† Jani Radebaugh,3† Ross A. Beyer,4,5

Tanguy Bertrand,6 François Forget,6 Francis Nimmo,7 Will M. Grundy,8

Jeffrey M. Moore,5 S. Alan Stern,9 John Spencer,9 Tod R. Lauer,10 Alissa M. Earle,11

Richard P. Binzel,11 Hal A. Weaver,12 Cathy B. Olkin,12 Leslie A. Young,9

Kimberly Ennico,5 Kirby Runyon,12 The New Horizons Geology, Geophysics andImaging Science Theme Team‡

The surface of Pluto is more geologically diverse and dynamic than had been expected,but the role of its tenuous atmosphere in shaping the landscape remains unclear. Wedescribe observations from the New Horizons spacecraft of regularly spaced, linear ridgeswhose morphology, distribution, and orientation are consistent with being transversedunes. These are located close to mountainous regions and are orthogonal to nearby windstreaks. We demonstrate that the wavelength of the dunes (~0.4 to 1 kilometer) is bestexplained by the deposition of sand-sized (~200 to ~300 micrometer) particles of methaneice in moderate winds (<10 meters per second). The undisturbed morphology of the dunes,and relationships with the underlying convective glacial ice, imply that the dunes haveformed in the very recent geological past.

Dunes require a supply of particulate ma-terial on a surface and a fluid boundarylayer to entrain the grains (i.e., wind, fordunes on a planet’s surface). They havebeen identified in some surprising loca-

tions: Contrary to predictions (1), Saturn’s moonTitan has a broad belt of linear dunes encirclingits equatorial latitudes (2), and despite the lackof a persistent atmosphere, eolian landforms(i.e., those related to wind) have also beensuggested to occur on comet 67P/Churyumov-Gerasimenko (3). On 14 July 2015, NASA’s NewHorizons spacecraft flew past Pluto, which pro-vided spectral data and imagery of the surfaceat resolutions as detailed as 80 m/pixel (4). Thecombination of Pluto’s low gravity (0.62 m s−1,or 1 16= that of Earth), sparse atmosphere [1 Pa (5)],extreme cold [~45 K (5)], and surface com-position [N2, CO, H2O, and CH4 ices (6)] madepre-encounter predictions of surface processeschallenging. However, pre-encounter speculationincluded that eolian processes, and potentiallydunes, might be found on Pluto (7), because, despitethe relatively thin atmosphere, the winds could

possibly sustain saltation (i.e., particle movementby ballistic hops) in the current surface conditions.We examined images from the Long Range Recon-naissance Imager (LORRI) instrument (8) on NewHorizons, taken during the probe’s closest ap-proach to Pluto, to search for landforms with themorphological and distributional characteristicsof dunes. We also searched spectroscopic datafrom the Multispectral Visible Imaging Camera[MVIC (9)] for evidence of sufficient sand-sized iceparticles to form dunes, and discuss how subli-mation may play a role in lofting these particles,enabling them to be saltated into dunes.

Observations from New Horizons

The surface of Pluto, as revealed byNewHorizons,is diverse in its range of landforms, composi-tion, and age (4, 10). One of the largest features,Sputnik Planitia (SP), is a plain of N2, CO, andCH4 ice [(6) and fig. S1] that extends acrossPluto’s tropics and at its widest point covers30° of longitude (Fig. 1A). Polygonal features onthe surface of SP, tens of kilometers across andbounded by trenches up to 100m deep (Fig. 1, Band C) have been interpreted as the result ofthermally driven, convective overturning of theice (11, 12), which, together with the uncrateredsurface of SP (4), suggests a geologically young[<500 thousand years (ka)] (11, 12) and activesurface. Much of the western edge of the ice isbounded by the Al-Idrisi Montes (AIM), a moun-tainous region with relief of up to 5 km. On theSP plain bordering these mountains, distinct,regularly spaced, linear ridges are evident withina belt of ~75 km from the mountain margin(Fig. 2A). They have positive relief as evidentfrom shadows consistent with the mountains.The ridges show pronounced spatial regularity(~0.4 to 1 km wavelength), substantial length/width ratios (sometimes >20 km length), con-sistent shape along these lengths, and the pres-ence ofmerging and bifurcation junctions (Figs. 1,C and D, and 2, D and E). These junctions are

approximately evenly spread between 47 north-facing bifurcations and 42 south-facing splits, andthere is no clear spatial patterning to the directionof junctions. Farther from the mountain margin,toward the southeast, the ridges become morewidely spaced and generally larger, while stillin isolated fields or patches. Dark streaks are alsofound across the surface of the ice, typically be-hind topographic obstacles, and have been inter-preted as wind streaks (4). These features indicatethat there are loose particles near and on the sur-face, as the streaks are thought to result from thedeposition of suspended, fine particles in the lee ofobstacles to wind flow (4, 5, 13) (Fig. 1, C and E).We have identified 357 pale-colored, linear

ridges on SP adjacent to the AIM (Fig. 2, A to C),as well as six darker wind streaks in addition tothe seven previously identified (4). The ridgesclosest to the SP/AIMmountain front are orientedapproximately parallel with it, and ridges fartherto the southeast shift orientation clockwise by~30° over a distance of ~75 km (Fig. 2, A and B);the ridges farther from the SP/AIM margin aresignificantly (Mann-Whitney U = −7.41; p <0.0001) more widely spaced (Fig. 2C). Beyondthe ~75-km-wide belt in which the linear ridgesare predominantly found, the morphology of thesurface changes, with preferential alignment ofthe ridges gradually disappearing (fig. S2), untilthe landscape is dominated by weakly aligned orunaligned, but still regularly dispersed, pits likelycaused by sublimation of the ice (14).Wind streaksadjacent to the SP/AIM border are perpendicularto the ridges and mimic the shift in orientationshown by the ridges (Fig. 3, A and B). Streakswithin the zone in which the ridges are found(i.e., <75 km from the SP/AIM border) are geo-graphically (i.e., clockwise from north) oriented113 ± 4° (1 standard deviation, s, with samplenumber n = 4), while more distant wind streaksare oriented significantly [(heteroscedastic Student’st=9.912; p < 0.001 (Fig. 3B)] differently at 153 ±10° (1s, n = 9).

Interpretation as dunes

The ridges found on western SP have morpho-logical similarities to dunes (Figs. 1, C and D,and 4, A to C). In addition to analog similarities,we argue that these landforms are most con-sistent with an initial eolian depositional origin(i.e., dunes) on the grounds that (i) a depositionalorigin is favored by the superimposition of manyof the dunes on the trenches bordering SP’s con-vective cells (Figs. 1D and 2, D and E); (ii) thedistribution of the dunes with pattern coarsen-ing (enlarging toward the southeast), away fromthemountains (Fig. 4C), is characteristic of dune-fields; (iii) their orientation, and systematicregional changes to this orientation, are morereadily explained by the wind regime than varia-tions in incoming solar radiation; (iv) the pres-ence of pronounced wind streaks, orthogonalto the dunes, demonstrates the potential efficacyof Pluto’s winds; (v) their location, on amethane-and nitrogen-dominated ice cap adjacent tomountains, is where the strongest winds anda supply of sediment might be expected; and

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1School of Geography, Earth and Environmental Sciences,Plymouth University, Drake Circus, Plymouth, Devon PL48AA, UK. 2Department of Geosciences, University of Cologne,Pohligstraße 3, 50969 Cologne, Germany. 3Department ofGeological Sciences, College of Physical and MathematicalSciences, Brigham Young University, Provo, UT 84602, USA.4Sagan Center at the SETI Institute, Mountain View, CA94043, USA. 5NASA Ames Research Center, Moffett Field,CA 94035, USA. 6Laboratoire de Météorologie Dynamique,Université Pierre et Marie Curie, Paris, France. 7University ofCalifornia Santa Cruz, Santa Cruz, CA, USA. 8LowellObservatory, Flagstaff, AZ, USA. 9Southwest ResearchInstitute, Boulder, CO, USA. 10National Optical AstronomyObservatory, Tucson, AZ 85726, USA. 11Department of Earth,Atmosphere, and Planetary Science, Massachusetts Instituteof Technology, Cambridge, MA 02139, USA. 12Johns HopkinsUniversity Applied Physics Laboratory, Laurel, MD, USA.*Corresponding author. Email: matt.telfer@plymouth.ac.uk†These authors contributed equally to this work. ‡The NewHorizons Geology, Geophysics and Imaging Science Theme Teamauthors and affiliations are provided in the supplementary materials.

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(vi) their differing morphologies and undeformedregular alignment differ from the randomlyaligned, shallow pits that border on the duneregions of SP (Fig. 4E and fig. S2) and the deeplyincised, discrete, aligned pits that can be foundtoward SP’s southern and eastern margins (Fig.4D). These pit-like features are morphologicallydistinct from the dune-like ridges farther northnear the AIM that we discuss here (Fig. 4, A andD). To test this hypothesis, we use amodel (15) toexamine the saltation of sand-sized (in this case,~200 to 300 mm) particles on Pluto. Once initiated,themodel indicates that saltation can be sustainedeven under the low (Earth-like; 1 to 10m s−1) windspeeds predicted at the surface today (16). How-ever, the model also suggests that an additionalprocessmay be necessary to initially loft particles(15). This can be accomplished by sublimation,which is capable of lofting particles, andwemod-el this process to find that particles can be en-trained. This function of sublimation is in additionto the role sublimationmayplay in erodingmaturedunes tomore altered forms,which is alsodiscussedin more detail below. Thus, under the current con-ditions, if there are sufficiently noncohesive sand-sized particulates on the surface of Pluto, we shouldexpect to find dunes.Terrestrial and planetary dunes that form

straight ridges can occur either perpendicular tothe wind, forming transverse dunes, or parallelto the net local wind regime, forming longitudinal(or linear) dunes, and regional variation in thealignment of such dunes on Earth is typicallyassociated withmeso- or large-scale atmosphericpatterns (17). Wind streaks are well known onVenus and Mars, are present even under thetenuous atmosphere of Triton, and are generallyconsidered to represent the wind direction (13).The presence of pronouncedwind streaks (Fig. 1C)within the dunefield, very nearly orthogonal tothe dune trends, suggests that the observed dunesare transverse forms (Fig. 3A). The transversenature of the dunes is further supported by thelack of consistency in bifurcation orientation;within dunefields oriented parallel to net sediment-transporting winds, such defects tend to clusterin terms of their orientation (18). The transverseorientation also shows that these ridges cannot besastrugi (erosional snow ridges that formparallelto net winds) (19), or other erosional features anal-ogous to yardangs (wind-carved ridges). The dunesin the northwestern portion of SP/AIM (Fig. 4A)are even more regularly spaced and parallel thanmany transverse dunes on Earth. Possible explan-ations for this include a highly consistent windregime, lack of topographic deflection of winds,or a smooth substrate.

Conditions for the formation of dunesand sublimation pits

The existence of dunes on the surface of Plutorequires three necessary criteria to be met. First,there must be a fluid atmosphere of sufficientdensity to make eolian transport possible. Sec-ond, there must be a granular material of a sizeand density, and with sufficiently low cohesion,that it can be entrained by winds. On Earth, this

role is typically played by sand-sized mineralgrains of a variety of compositions, includingsnow and ice. Third, given the high wind speedsneeded to lift surface particles against cohesionforces (20) (Fig. 5), a specific mechanism mustexist to loft large quantities of ice particles intothe atmospherewhere they are available for eoliantransport. The presence of these criteria alone isnecessary but not sufficient to identify the surfacefeatures as dunes. To justify our interpretation ofthese features as being dunes, we also examine theconditions required for the other most likelycandidate: aligned sublimation pits.

Winds

The orientations of the dunes and the windstreaks change locally, and consistently; in thecase of the dunes, over a distance on the orderof 10 to 102 km. This implies that the topographyand/or surface composition has influenced the

local wind regime, as was anticipated (21). Theseorientations are consistent with sublimation-driven and topographic mechanisms for thehorizontal displacement of the atmosphere, aswinds are generated by a gravity-driven flowtoward lower regions. Modeling of Pluto’s cur-rent atmosphere suggests that surface windson the order of 1 to 10 ms−1 are possible; theyshould be strongest where there are topographicgradients and when driven by sublimation ofsurface ices by sunlight (15). The location of thedunes at the western margins of the SP and AIMshould thus be among the windiest locationson the known regions of Pluto. Aswith Earth andMars, once grain transport along the surface ofPluto has begun, increased efficacy of grain-splash(the ejection of new particles due to grains insaltation colliding with the ground) promotes ahysteretic effect that further sustains sedimentflux (22, 23). We use a numerical model (15) to

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Fig. 1. New Horizons flyby imagery of landforms attributed to eolian origins. All images areunrectified, and thus all scales are approximate. Color-composite MVIC images are shown here forcontext; dune identification was performed on grayscale LORRI images (shown below). (A) Overviewof Pluto centered on ~25° latitude, ~165° longitude, showing the locations of images (B) and (E)and Fig. 3A and fig. S3 (47). (B) The spatial context for SP and the AIM mountains to the west (48).Insets (C) and (D) show details of the highly regular spatial patterning, which we attribute toeolian dune formation, and two newly identified wind streaks (arrows x), along the margins of theSP/AIM border. Here the dunes show characteristic bifurcations (arrows y) and a superposition withSP’s polygonal patterning (arrow z), suggesting a youthful age for these features (49). (E) Twofurther wind streaks on the surface (x’), downwind of the Coleta de Dados Colles (4). These windstreaks, farther from the SP/AIM margin, are oriented differently than those close to the icefield’sedge and are still roughly orthogonal to the dunes there (50).

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demonstrate that despite the high wind speedsneeded for initial eolian entrainment, eoliantransport can, once established, be sustainedwith wind speeds of ~10 m s−1 (Fig. 5).

Sediment supply

Although terrestrial dunes are typically associatedwith quartz, basalt, or gypsum sand, other ma-terials can form the grains for dune development.Snow dunes of a very large scale are observedin the center of the Antarctic continent (24); onTitan, it is generally assumed to be atmosphere-derived organics, perhaps initially tholins, whichform the equatorial belt of giant dunes (25).Whereas tholins are thought to form the darkpatches of Pluto’s equatorial regions (6), thedunes evident on SP are light in color and arethus not formed from the same complex, organic,photochemically derived haze seen in Pluto’satmosphere (4). The most likely candidates arethus N2 and CH4 ices. The surface of SP hasgenerally been interpreted as predominantlycomposed of N2 ice (4, 5), just as solidified ni-trogen snows are believed to account for Triton’sice-covered surface (26, 27). The zone in whichthe ridges occur is coincident with the latitudesin which net N2 condensation occurs over thecourse of a Pluto year (16, 28) (fig. S3). However,recent analyses suggest that the compositionmay be a more complex mix of N2, CH4, and COices (29). Our analysis of data from the MVICinstrument, using a CH4 filter (15), suggests that

the location of the ridges and streaks coincideswith a region of enhanced CH4 ice content (fig.S4). To the west of SP, the Enrique Montes inCthulhu Macula (CM) have been shown to becapped withmethane, presumably as the resultof condensation or precipitation (29, 30). CH4

ice retains hardness and rigidity under Plutosurface conditions, which is ideal for saltationand dune formation, whereas N2 ice is likely tobe softer. These constraints lead us to concludethat the dunes are formed predominantly ofgrains of methane ice, though we do not ruleout that there could also be a nitrogen ice com-ponent. The presence of transverse forms, in-dicating sediment-rich local conditions, asopposed to more sediment-starved isolatedbarchans (discrete, crescentic dunes), suggeststhat locally, the sediment supply to this region ofSP must be, or must have been, abundant. Giventhe strength of the color and boundary delinea-tions of methane in the AIM (fig. S3), the meth-ane ice may be quite thick and perhaps similarto valley glaciers in these isolated regions. Ifsuch high-altitude methane snowpack is a re-gular, seasonal occurrence, this may be a substan-tial reservoir fromwhich to derive the abundantsand across the northwestern surface of SP re-quired to form these transverse dunes.

Grain size

Credible sediment sizes are required for duneformation under the likely eolian regime. The

grain sizes proposed for nitrogen ices (e.g., onTriton) have varied from micrometer (31, 32)to meter scale (33). We develop a method (15) toapproximately constrain average grain size (d)and formative wind speed (U) from the meancrest-to-crest distance, or wavelength (l), of thetransverse dunes. For eolian dunes, the relevantlength scale controlling this wavelength is thesaturation length (Lsat) of the sediment flux,which is the distance needed by the flux toadapt to a change in local flow conditions. Bycombining theory (34), which predicts Lsat asa function of wind speed and attributes of sedi-ment and atmosphere, with a mathematicalmodel (35) for l as a function of Lsat and U,we obtain the values of d and U that are con-sistent with l. These values are shown in fig. S5,for l ≈ 700 m and l ≈ 560 m, which correspondto the transverse dunes far from and near to themountainous area of Fig. 1, respectively. Giventhat expected formative wind speeds on Plutoare not larger than 10 m s−1 (16), fig. S5 impliesthat grain size does not exceed ~370 mm and ismost probably in the range between 210 and310 mm. The spectral response of the MVIC CH4

filter offers an additional constraint on the pos-sible grain sizes observed, as Hapke modelingof the scattering within a granular mediumprovides a grain size–dependent control on theequivalent width of the absorption band. Wefind (15) that the observed response is consistentwith a granular medium of ~200 to 300 mm.

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indicates the mean trend of the border of SP and the Al-Idrisi Montesin this area (194°). (C) Frequency of dune spacings in clusters close to [redline representing dunes within the red dashed line of (A)] and far from[green line representing dunes within the green dashed line of (A)] theicefield/mountain interface. Dunes farther from the mountains are morewidely spaced (�x = 700 m) than those close to the mountains (�x = 560 m).(D) Detail of the image interpretation process of the highest-resolutionswath, showing linear ridges, which sometimes bifurcate but areotherwise notable for their regularity. (E) The same image with ridgelines highlighted.

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LoftingAlthough eolian transport can be maintainedunder Pluto’s current wind regime, the speedsnecessary for initial entrainment are orders ofmagnitude greater than those believed to bepresent at Pluto’s surface (Fig. 5). An additionalprocess is thus likely to be necessary to initiateeolian activity. In Sputnik Planitia, this processmay be related to the intense, solar-driven sub-limation of surface ices that injects more than103 m3 m−2 of gas into the atmosphere everyafternoon [figure 8 of (16)]. When sunlightpenetrates through, the upper layers of semi-transparent ice particles are lofted, sometimesat high vertical velocities, due to a mechanismoften referred to as a solid-state greenhouse(36). Therefore, initial entrainment of ice grainsthat eventually form dunes may result from sub-limating subsurface ice, as has been observed in thethin atmospheres of Mars’ northern polar region(37) and proposed for comet 67P/Churyumov-Gerasimenko (38, 39) and Triton (24, 25). Model-ing (15) suggests that subsurface N2 sublimationunder Pluto surface conditions is capable oflofting even the densest candidate particles [N2

ice, at 1030 kg m−3, is denser than CH4 ice, at494 kg m−3 (40)] with sizes ~200 mm, even at0.1 Pa; within the range of both Pluto’s atmo-spheric pressure and the solid N2 vapor pressure.Surface ices of mixed composition offer an ad-ditional potentialmechanism for facilitating grainlofting. At the nitrogen frost point temperatureof 63 K (11), pure methane ice particles mixedwith nitrogen should not sublimate at all. Asmethane particles are slightly heated by theSun, they should enable the sublimation of thenitrogen ice that they touch and thus be readilylofted into the atmosphere. Similar processeshave recently been suggested for the migrationof tholin deposits on the surface of Pluto (41).Past periods of higher atmospheric pressures,which have been suggested (42), could facilitateinitial entrainment due to increased efficacy ofeolian processes.

Sublimation

The landscape of SP contains evidence ofsublimation-driven landforms (4, 7, 14), andthis process is important in shaping parts ofPluto’s surface. We consider whether the land-forms described here are more consistent withorigins attributable to eolian or sublimation pro-cesses. Locally, sublimation pits are deeply incisedand may align to form linear troughs up to tensof kilometers long and up to ~1 km deep (4, 7).Frequently, and especially toward the southernand eastern margins of SP, any alignment is sub-sequently heavily deformed, presumably driven byglacial flow and convective overturning. Analoglandforms on Earth are provided by sublimation-driven textures of snow and ice surfaces: ablationhollows (suncups) and penitentes (14, 43). On Earth,ablation hollows on snow may become aligned toleave ridges (penitentes), which align themselvesto within ±30° of east-west (i.e., the annual meannet Sun path) (44). Although the orientation of anypenitentes on Pluto is likely to be more complex

and seasonally dependent, they are only likely toform wavelengths in excess of ~1000 m (45). It ispossible that sublimation has acted upon alreadyformed dunes in some regions (Fig. 2A). In polarregions on Earth, wind-driven snow or ice grainscan produce dunes, which then become hardenedby sintering and begin to undergo modificationby wind and sublimation processes, thus changingfrom depositional to erosional landforms (44, 45).Given the tendency of ices to sinter together un-der the right conditions, this could also happen inthe CH4 or N2 ices of Pluto’s dunes. Sublimationerosion of Pluto’s dunes may enlarge and roundthe areas between the dunes, and sharpen thedune crests while preserving the overall dune ori-entation and spacing. This morphology may beseen just at the resolution limit in the featuresfarthest from the mountains in Fig. 2A (enlargedview in fig. S2). This is supported by modeling (15)of the net accumulation of ices across Pluto’s sur-face during the past two (Earth) centuries (fig. S4),which suggests that for the past ~30 Earth years,the dunefield has been experiencing net sublima-

tion. Some of these features may have progressedso far toward being erosional that we have notidentified them as dunes (fig. S2).

Age

An upper limit on the age of the dunes, whichsit atop the ice of the western margins of SP,is imposed by the recycling rate of the uppersurface of the convectional cells within the ice(i.e., <500 ka) (11, 12). This overturning of thesubstrate, inferred from the complete absenceof identified craters on SP, provides an ageconstraint for superficial landforms that is notavailable for dunes on other solar system bodiesand implies a geologically and/or geomorpho-logically active surface (4, 10, 46). Surface fea-tures, undistorted by the convectional overturningwithin the ice, must be much younger than thetime scales of convection, and therefore closerto the time scales of Pluto’s strong seasons (i.e.,terrestrial decades to centuries). Further evidencethat the dunes form on a time scale substantiallyshorter than that of the convection is suggested

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by the superposition of the dunes over the de-pressions at the cell margins (Fig. 1G).

Summary and conclusions

We have presented evidence that the highlandsadjacent to SP accumulate methane. The ridged,dune-like landforms nearby, and accompanyingwind streaks, are rich in methane relative totheir underlying substrate. Although the windspeeds needed for eolian entrainment are higherthan the likely wind speeds present on the sur-face, sublimation provides a credible mechanismfor lofting grains. Numerical sediment transportand spectralmodeling suggest that thesemethanegrains are ~200 to 300 mm. Our models suggestthat eolian transport is highly effective underPluto surface conditions once initiated. An amplesediment supply appears to be available from aseasonally abundant snowpack in the adjacentmountains. The result is the formation of trans-verse dunes, as we identify in the images fromNewHorizons. The orientation of the dunes per-pendicular to the wind is supported by the localtopography and surface, and accompanying windstreaks. The presence of these dunes indicatesan active atmosphere that produces geologicallyyoung landforms.

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10 km

A Pluto

5 km

C Earth

10 km

B Earth

10 km

E Pluto

D Pluto

10 km

NN

N

F Mars

500 m

N

N

Fig. 4. Analogs and comparison with sublimation features. (A) Details of the dunes on westernSputnik Planitia, centered on 34.35° 159.84° (location shown in Fig. 1). (B) Analogous terrestrial transversedunes of the Taklamakan Desert, western China [Image credit: image CNRS/SPOT, DigitalGlobe andcourtesy of Google Earth], and (C) the same location down-sampled to a relative resolution similar to that ofthe Pluto dunes (i.e., ~5 to 10 pixels per crest-crest spacing). (D) The aligned and distorted sublimationfeatures abundant on southern and easternSP (image centered on−4.78° 189.48°) and (E)weakly aligned torandomly oriented, shallow sublimation pits. (F) An example of a landscape revealing both eolianand sublimation-derived landforms atMars’ southern polar ice cap from theMars Reconnaissance Orbiterreveals both dark eolian bedforms (dunes and ripples), as well as sublimation pits developing in theunderlying CO2 ice. [Image credit: NASA/JPL/University of Arizona, ESP_014342_0930_RED]

Fig. 5. Minimal threshold windspeeds. The wind speedsrequired for initiation (Uft, orangeline) and continuation (Ut,black line) of saltation on Pluto,at a reference height of 10 mabove the soil, were computedfor different values of theaverage particle diameter (15).The dashed horizontal lineindicates maximum likelywind speeds at Pluto’s surface.

0 400 800 1200 1600 2000 2400Average particle diameter, (µm)

101

102

103

Thr

esho

ld w

ind

velo

city

at 1

0 m

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m s

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threshold for transport initiation, ftthreshold for transport continuation, t

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ACKNOWLEDGMENTS

We thank everyone involved, from concept to data retrieval, withthe New Horizons mission. This research has made use of theUSGS Integrated Software for Imagers and Spectrometers(ISIS). Funding: E.J.R.P. thanks the German ResearchFoundation for grant RI2497/3-1. All New Horizons teammember authors are funded by the NASA New Horizons Project.Author contributions: M.W.T. conducted the spatial analysisand image interpretation, coordinated the research, and co-wrote the paper. E.J.R.P. developed and conducted thenumerical modeling and co-wrote the paper. J.R. coordinatedthe research and co-wrote the paper. R.A.B. produced andprovided LORRI mosaicking. T.B. and F.F. provided data on

surface/atmosphere exchanges. F.N. performed calculations onthe effectiveness of sublimation modeling. W.M.G. conductedthe Hapke modeling. J.M.M., S.A.S., and J.S. contributed to themanuscript. T.R.L. produced and provided LORRI mosaicking.R.P.B. and A.M.E. provided circulation model data. H.A.W., C.B.O.,L.A.Y., and K.E. are project scientists and contributed to themanuscript. K.R. provided discussion of ideas. Competinginterests: There are no competing interests to declare. Dataand materials availability: The LORRI data are archived in thePlanetary Data System (PDS) Small Bodies Node at https://pds-smallbodies.astro.umd.edu/holdings/nh-p-lorri-3-pluto-v2.0/.MVIC data are available via the PDS at https://pds-smallbodies.astro.umd.edu/holdings/nh-p-mvic-3-pluto-v2.0/

SUPPLEMENTARY MATERIALS

www.sciencemag.org/content/360/6392/992/suppl/DC1The New Horizons Geology, Geophysics and Imaging ScienceTheme TeamMaterials and MethodsFigs. S1 to S5References (51–69)

6 July 2017; accepted 19 April 201810.1126/science.aao2975

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Dunes on Pluto

Science Theme TeamCathy B. Olkin, Leslie A. Young, Kimberly Ennico, Kirby Runyon and The New Horizons Geology, Geophysics and ImagingGrundy, Jeffrey M. Moore, S. Alan Stern, John Spencer, Tod R. Lauer, Alissa M. Earle, Richard P. Binzel, Hal A. Weaver, Matt W. Telfer, Eric J. R. Parteli, Jani Radebaugh, Ross A. Beyer, Tanguy Bertrand, François Forget, Francis Nimmo, Will M.

DOI: 10.1126/science.aao2975 (6392), 992-997.360Science 

, this issue p. 992; see also p. 960Sciencedunes form under Pluto conditions will help with interpreting similar features found elsewhere in the solar system.the atmosphere by the melting of surrounding nitrogen ice or blown down from nearby mountains. Understanding how sand-sized grains of solid methane ice transported in typical Pluto winds. The methane grains could have been lofted intoSputnik Planitia region on Pluto (see the Perspective by Hayes). Modeling shows that these dunes could be formed by

used images taken by the New Horizons spacecraft to identify dunes in theet al.67P/Churyumov-Gerasimenko. Telfer Wind-blown sand or ice dunes are known on Earth, Mars, Venus, Titan, and comet

Methane ice dunes on Pluto

ARTICLE TOOLS http://science.sciencemag.org/content/360/6392/992

MATERIALSSUPPLEMENTARY http://science.sciencemag.org/content/suppl/2018/05/30/360.6392.992.DC1

CONTENTRELATED http://science.sciencemag.org/content/sci/360/6392/960.full

REFERENCES

http://science.sciencemag.org/content/360/6392/992#BIBLThis article cites 56 articles, 10 of which you can access for free

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