AHceb

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Nhc1

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AHcp

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AHlu2

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Figure 5

Figure 4

Figure 7

Figure 2

Figure 3

Figure 8

Figure 6

Canillo

Ehden

Zaranj

Doba

Phedra

Tavua

Linpu

Torbay

Platte Aban

Sinda

Marbach

Pina

Imgr

Telz

Brush

Ikej

Tomari

Souris

H E P H A E S T U S F O S S A E

Xui

U T O P I A P L A N I T I A

H

e

p

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N E P E N T H E S M E N S A E

N E P E N T H E S

M E N S A E

A M E N T H E S

C A V I

N E P E N T H E S

P L A N U M

N E P E N T H E S P L A N U M

A M E N T H E S C A V I

T E R R A C I M M E R I A

125°

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120° 121° 122° 123° 124°

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115° 116° 117° 118° 119°

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Figure 8. Image showing an example of the narrow troughs (black 

arrows), which commonly bound Amenthes Cavi. We interpret these as 

fractures that occur in the Nepenthes flow unit (Htnf). Note the braided 

channel-like depressions (white arrows) that emanate from the narrow 

grooves. We interpret these channel features as forming through the 

eruption of subsurface fluids, which emplaced the Utopia lowland 1 unit 

(Hlu1), the approximate margin of which is identified by the dashed 

line. Excerpt of Context Camera image number P03_00280_1945 

(centered at lat 13.58° N., long 119.46° E.; location shown on map). 

5 KILOMETERS

Htnf

Htnf

Hlu1

N

Figure 7. Image showing small tholi (mounds) located in Nepenthes 

Planum. Mounds (white arrows) have ovoid planimetric shape and 

commonly have small cone-shaped landforms at their apex. Mounds 

are often associated with crenulated (wrinkle) ridges and lobate scarps 

(black arrows). We interpret the small tholi as mud volcano-like 

constructs formed through the vertical and (or) horizontal contraction 

of fluid-rich sediments (Tanaka and others, 2003b; Skinner and 

Tanaka, 2007; Skinner and Mazzini, 2009). Alternatively, these 

features may have formed by igneous volcanism, as posited by Brož

and Hauber (2013). Excerpt of Thermal Emission Imaging System 

image number V27503026 (centered at lat 11.98° N., long 124.90° E.; 

location shown on map).

5 KILOMETERS

wrinkle ridge

Htnf

wrinkle ridge

wrinkle ridge

N

Figure 6. Image showing complexly overlapping lobate materials and source vents 

located between Nepenthes Planum and Amenthes Cavi. The Nepenthes vent unit (Htnv) 

occurs throughout Nepenthes Planum as isolated and coalesced pitted cones as well as 

low-relief mounds. We interpret these features as eruptive vents for the surrounding 

Nepenthes flow unit (Htnf), which characteristically contains lobate scarps (black 

arrows) suggestive of flow-like emplacement. Unit Htnf contains smooth and rough 

surface textures, which we interpret as differences in erupted material and (or) 

post-emplacement modification. The Utopia 1 unit (Hlu1) occurs as smooth material that 

occupies Amenthes Cavi, which are commonly bounded by narrow trough (white 

arrows) interpreted to be fractures. Note the occurrence of a large pitted cone along these 

subdued grooves, suggesting these grooves are the surface expression of fractures that 

served as pathways for erupted material. Excerpt of Thermal Emission Imaging System 

image mosaic (centered at lat 16.05° N., long 111.50° E.; location shown on map).

5 KILOMETERS

Hlu1

Htnf

(rugged)

Htnf

(rugged)

Htnf

(smooth)

Nhc1

Htnv

Htnv

Htnv

Alban

Sinda

AHc

N

Figure 5. Image showing raised sinuous ridges and depression in the 

Cimmeria 3 unit (HNhc3) between Nepenthes Mensae and Terra 

Cimmeria. We interpret the raised ridges (black arrows) as inverted 

channels formed by the erosion of unit HNhc3, which here forms the 

floor of a 25-kilometer-diameter irregularly shaped basin. Unit erosion 

is evidenced by raised ridges that transition into sinuous depressions 

(black bracket), which corresponds to a south-north gradation from a 

rough to smooth surface. White arrows identify grooves and 

hummocks that mark the eroded margin of unit HNhc3. Excerpt of 

Thermal Emission Imaging System image number V38543032 

(centered at lat 10.60° N., long 110.27° E.; location shown on map).

5 KILOMETERS

N

HNhc3

HNhc3

Nhc1

Nhc1 Nhc1

Nhc1

smooth surface

rough surface

Figure 4. Image showing braided, sinuous channels in the Cimmeria 3 

unit (HNhc3) circumventing high-standing massifs of the Cimmeria 1 

unit (Nhc1) in Nepenthes Mensae. The channels (white arrows) 

migrate around the lobe-like southern margins of the Nepenthes flow 

unit (Htnf), implying temporal overlap of the emplacement of units 

HNhc3 and Htnf. The lobate scarps (black arrows) are characteristic of 

unit Htnf. Excerpt of Thermal Emission Imaging System image 

number V27416032 (centered at lat 10.26° N., long 114.57° E.; 

location shown on map).

5 KILOMETERS

Nhc1

Nhc1

Nhc1

Nhc1

HNhc3

HNhc3

Htnf

N

Figure 3. Image showing an example of the troughs of Hephaestus 

Fossae in the northeastern part of the map region. The troughs occur in 

the Utopia 2 unit (AHlu2). Small pitted cones are common, where they 

are either isolated or grouped into narrow, arcuate ridges (black 

arrows). Ridges of small pitted cones are aligned on either side of 

shallow, narrow depressions (white arrows), providing evidence that 

these cones and narrow, arcuate ridges pre-date the formation of 

Hephaestus Fossae. Excerpt of Thermal Emission Imaging System 

image number V26667039 (centered at lat 19.43° N., long 124.27° E.; 

location shown on map).

5 KILOMETERS

N

AHlu2

AHlu2

Figure 2. Image showing landforms associated with the southern 

margin of the Utopia lowland 2 unit (AHlu2). South-facing lobes 

(black arrows) onlap and surround low-relief topographic 

promontories, which are mapped and interpreted as erosional vestiges 

of the Nepenthes flow unit (Htnf). Narrow, arcuate ridges have similar 

orientations as the marginal lobes but are commonly made up of small 

diameter pitted cones (white arrows). The cones locally form a dense 

field, particularly on the south side of knobs (labeled “knobby”). 

Excerpts of Thermal Emission Imaging System image numbers 

V39182003 and V19691008 (centered at lat 19.04° N., long 122.94° 

E.; location shown on map).

5 KILOMETERS

N

Hlu1

Htnf

Htnf

AHlu2

AHlu2

knobby

Htnf

Htnf

Htnf

Figure 1. Color shaded-relief image of the Nepenthes Planum region of Mars. Geologic units 

grouped in this map are based on regions indicated on the left. Constructed from a digital 

elevation model of Mars Orbiter Laser Altimeter (MOLA) data (463 meters/pixel), an artificially 

illuminated MOLA hillshade (illumination from northwest), and a Thermal Emission Imaging 

System (THEMIS) daytime infrared image (IR) mosaic (100 meters/pixel). 

-5020 -4153 -3311 -2423 -1580 -692 104 969 METERS

ELEVATION

A m e n t h e s C a v i

A m e n t h e s C a v i

Hephaestus

 Fossae

Marbach

Linpu

Tavua

Phedra

Zaranj

Canillo

Doba

Ehden

U T O P I A P L A N I T I A

N E P E N T H E S P L A N U M

N e p e n t h e s M e n s a e

N e p e n t h e s M e n s a e

Hephaestus Rupē s

Hephaestus Rup ē s

Hephaestus Rup ē s

Utopia region Nepenthes region Cimmeria region

T E R R A C I M M E R I A

110° E

22.5° N

7.5° N

125° E

Figure 3

Figure 2

Figure 6

Figure 5 Figure 4

Figure 7

Figure 8

Contact—Dashed where approximately located; 

internal contacts shown in impact crater units 

mark superposition relations

Ridges

Crenulated (wrinkle) ridge crest

Narrow, arcuate ridge crest—Unit AHIu2 only

Depressions

Subdued groove—Size of symbol may vary 

Trough—Dashed where discontinuous

Channel—Locally forms positive relief sinuous 

ridges

Scarps

Base of scarp—Barb points downslope

Lobate scarp—Hachures point downscarp

Crater rims—For all impact craters >5 kilometers in 

diameter

Raised rim of impact crater

Subdued, degraded, or buried rim of impact 

crater

Large pitted cone—1.9 to 9.1 km in diameter

Small pitted cone—~500 m and ~1.0 km in diameter

Small tholi—2.6 to 6.6 km in diameter

Rugged surface—Unit Htnf only

EXPLANATION OF MAP SYMBOLS

Unit label Unit definition Additional characteristics Interpretation

LOWLAND PROVINCE

Unit name

DESCRIPTION OF MAP UNITS

[Note: Unit groups, names, and labels are discussed in the accompanying pamphlet. Unit definitions are based exclusively on characteristics observed in Thermal Emission Imaging System (THEMIS) camera daytime infrared range mosaics and include morphologic character, interior and marginal 

landforms, infrared brightness or albedo (where diagnostic), and cross-cutting and embayment relationships. Additional characteristics are based on THEMIS visible range images (image numbers denoted by “V”) and Context Camera (CTX) visible range images (image numbers denoted by “P”, “B”, 

or “G”). See Geologic Summary in pamphlet for further discussion of map units.] 

Utopia region units

Narrow, arcuate ridges frequently made up of small pitted cones 

(V18618016). Hummocks dominate intersecting arcuate ridges 

(V27491028). Marginal lobes ramp onto (V19691008) and surround 

(P14_006671_1983) knobs and plateaus. Unit onlaps and buries ejecta 

of some large diameter (>5 km) craters (B20_017589_2003) 

Sedimentary plains deposited by local to regional outflow channel and 

(or) atmospheric fallout. Lobe and ridge morphologies may reflect 

deposition or modification, perhaps by liquefaction. Thickness 

uncertain, though southward thinning implied by onlap relations 

Smooth, undulating, to hummocky unit located in southern Utopia 

Planitia. Margin made up of south-facing lobes as much as tens of 

kilometers across. Contains dense networks of narrow, arcuate ridges 

and aligned, small pitted cones. Circular, narrow fractures and scarps 

frequent 

AHIu2

Embays narrow fractures of the Nepenthes flow unit (Htnf) 

(P19_008609_1948). Crenulated ridges common in depressions of 

Amenthes Cavi (G03_019382_1928). Locally surrounds the 

Nepenthes vent unit (Htnv) (V16509009) 

Sedimentary and (or) volcanic plains deposited as low viscosity flows. 

Erupted from fractures that surround Amenthes Cavi, perhaps 

triggered by surface impact or seismic events. Close association with 

Amenthes Cavi indicate contemporaneous origin. Deformed by local 

contraction 

Smooth, planar unit located in (and extending north) of Amenthes 

Cavi. Abuts and partly buries outer ejecta of Marbach and Phedra 

craters. Low-relief knobs, plateaus, and scarps common, oriented 

north-south. Buried and partly buried impact craters frequent 

HIu1

Utopia 2 unit

Utopia 1 unit

TRANSITIONAL PROVINCE

Rugged texture locally defined by closely spaced hummocks 

(V27516027) and sharply crested hills, swales, or ridges 

(P21_009374_1964). Complexly overlapping lobes dominant 

(P21_009163_1958). Buries some cones of the Nepenthes vent unit 

(Htnv) (V26006025). Channels that emanate from subdued grooves 

around Amenthes Cavi are frequent (P03_002280_1945, 

G03_019382_1928) 

Lava and (or) sedimentary flows erupted from large pitted cones and 

mounds of the Nepenthes vent unit (Htnv). Variable rugged to smooth 

texture results from different eruptive styles and (or) erosional 

modification. Gradation with the Nepenthes vent unit (Htnv) indicates 

contemporaneous origin 

Rugged to smooth, undulating unit that dominates Nepenthes Planum 

and Amenthes Cavi. North-south- and east-west-oriented ridges and 

knobby ridge segments common. Emanates from and surrounds the 

Nepenthes vent unit (Htnv) cones. Contains narrow, subdued grooves 

that define the depressions of Amenthes Cavi. Makes up plateaus and 

knobs in Utopia 1 (AHlu2) and 2 units (Hlu1). Buried and partly 

buried impact craters abundant. South-facing lobes make up part of 

the unit’s southern margin 

Htnf

HIGHLAND PROVINCE

Overlapping circular depressions common at centers of cone-shaped 

outcrops (V27054039). Subtle knob or mound common near center of 

mound-shaped outcrops (B20_017549_1923). Unit locally associated 

with narrow fractures (G04_019712_1964) 

Constructional vents deposited by effusively erupted lava and (or) 

fluidized sediment (mud breccia). Morphologic variation due to 

different eruptive styles, volatile content, and (or) tapping depth. 

Gradation with the Nepenthes flow unit (Htnf) indicates 

contemporaneous origin 

Smooth, sloping unit located in Nepenthes Planum and some 

depressions of Amenthes Cavi. Isolated and coalesced, cone- and 

mound-shaped outcrops diagnostic. Cones locally emanate lobes of 

the Nepenthes flow unit (Htnf) 

Htnv Nepenthes vent unit

Nepenthes flow unit

Nepenthes region units

Occupies depressions between knobs and plateaus of the Cimmeria 1 

unit (Nhc1; P15_006737_1901 and G02_019079_1899). Ridge 

crenulations common (V27778024). Burial by the Cimmeria 3 unit 

(HNhc3) locally mutes ridge morphology (V06300021) 

Highland regolith consisting of various undifferentiated 

amalgamations of impact units and degraded sedimentary plains 

emplaced by fluvial, colluvial, and (or) lacustrine processes. Local 

volcanic rocks and sediments likely. Deformed by regional and (or) 

local tectonic compression. Grades with older Cimmeria 1 unit (Nhc1) 

and younger Cimmeria 3 unit (HNhc3) 

Smooth, undulating, ridged, and moderately cratered unit expanses 

located in inter-crater plains in northern Terra Cimmeria; some 

exposures occur in Nepenthes Mensae. Forms parts of the floors of 

impact basins. Speckled bright-dark surface common 

Nhc2

Massifs made up of rugged undulations and hillocks with sinuous 

grooves and linear gullies (V05214009). Crenulated ridges commonly 

transect massifs and plateaus (V05214009). Subdued grooves and 

troughs deform some knobs and plateaus (V06587016, 

B21_017747_1933) 

Intact and fractured regolith and crustal rocks. Massifs composed of 

crustal rocks uplifted by basin forming impacts. Intermixed 

impact-related, volcanic, and erosional rocks and sediments likely. 

Knobs and plateaus formed by extension along highland-lowland 

boundary 

Rugged, densely cratered, high-standing unit composed of massifs, 

knobs, plateaus, and crater basin rims in northern Terra Cimmeria. 

Forms high-relief knobs and plateaus in Nepenthes Mensae and 

Nepenthes Planum. Flat-floored, rimmed and rimless impact basins 

common. Ridges, scarps, and subdued grooves frequent 

Nhc1

Cimmeria region units

Margins locally lobate and show clear abutment of transitional knobs 

and plateaus (V06587016). Pits and hummocks characteristic 

(V31184011; B19_016956_1884). Margins frequently defined by 

low-relief scarps between knobs and plateaus (P13_006223_1919) 

Intact and degraded sedimentary plains emplaced by fluvial, colluvial, 

and (or) lacustrine processes. Braided ridges are likely inverted 

channels. Channel convergence indicates northward transportation. 

Locally overlain by (and perhaps interbedded with) dust mantles 

Smooth, sloping, moderately cratered unit located on slopes and 

between knobs and plateaus of Nepenthes Mensae and on floors of 

impact and basins in northern Terra Cimmeria. Narrow, braided 

valleys and ridges common. Forms patches of bright, sloping, and 

hummocky surface at the margins of some highland basins 

HNhc3

Cimmeria 2 unit

Cimmeria 1 unit

Cimmeria 3 unit

WIDELY OCCURRING

Crescentic ridges, hummocks, and lineaments oriented radial to crater 

center common (V18094017). Shallow, sinuous grooves with fan-like 

extensions evident but rare (P18_008029_1951) 

Rocks and sediments emplaced by impact-related ejection of target 

units. Layered, lobate ejecta indicates water- and (or) ice-rich target 

rocks 

Hummocky, lineated, and lobate unit located around all impact craters 

with diameters ≥16 km. Multiple, rugged, overlapping, 

outward-facing lobes characteristic. Hummocks typical near crater 

rim, grading outwardly into lobes and lineaments 

AHcea

Smooth to undulating surface with overlapping lobes and lineaments 

oriented radial to crater center common (V28826014) 

Layered sediment and breccia formed by the impact into – and 

ejection of – stratified units. Layered, lobate ejecta indicates waterand (or) ice-rich target rocks. Smooth surface indicates uniform flow 

with no velocity gradient during emplacement 

Smooth, lineated, and lobate unit located around all impact craters 

with diameters ≥16 km. Multiple, smooth, overlapping, 

outward-facing lobes characteristic. Located peripheral to crater ejecta 

unit, facies a (AHcea) 

AHceb

Impact crater units

Lineaments and sinuous striations common on ejecta lobes 

(V27441027). Floor peaks and wall slumps common on craters with 

diameters >8 km (V27129025) 

Rocks and sediments emplaced by impact-related ejection and 

deformation of target units. Pervasive layered and lobate ejecta 

morphologies indicate water- and (or) ice-rich target rocks 

Ejecta, rim, wall, and floor units of well-preserved impact craters with 

diameters between 5 and 16 km. Layered and lobate ejecta 

morphologies well-preserved and pervasive 

AHc

Crater ejecta unit, facies a 

Crater ejecta unit, facies b 

Crater unit, undivided

Locally hummocky to undulating where extending onto crater floor 

(V26792019). Concentric ridges and grooves common between 

hillocks (B18_016679_1897) 

Layered sediment and breccia formed by the impact into – and 

ejection of – stratified units. Layered, lobate ejecta indicates waterand (or) ice-rich target rocks. Smooth surface indicates uniform flow 

with no velocity gradient during emplacement 

Rugged unit composed of hillocks, blocks, and scarps located near 

interior base of crater rim. Discontinuous horizontal to slightly tilted 

terraces common 

AHcw

Low-relief surface pits, scallops, and sinuous scarps common 

(V19117013). Layering locally exposed (B20_017457_1903) 

Impact-melt and (or) impact-generated fines, modified by 

de-volatilization of interstitial water and (or) ice reservoirs. Likely 

includes post-impact sedimentary fill 

Smooth, planar to sloping, locally pitted unit located between interior 

rim and central peak of impact craters with diameters ≥16 km 

AHcf

Rim crest often splays into two or more closely spaced, discontinuous, 

and sub-parallel scarps or ridges (V19117013). Interior rim wall 

exposes layers; lower slopes smooth to lineated (B21_017958_1957) 

Upturned target rocks and sediments, locally deformed by mass 

wasting 

Rugged unit that defines the continuous to discontinuous, sharply 

crested rim scarp of all impact craters with diameters ≥16 km. Steep 

interior, basin-facing wall with narrow grooves and gullies 

AHcr

Crater wall unit

Crater floor unit

Subdued to sharply crested radial ridges common (V19117013, 

V26580031). Smooth to etched surface frequent (G02_019145_1942, 

P15_006895_1894) 

Deformed, fractured, and uplifted materials of the pre-impact surface. 

Central pit perhaps formed because of vaporization and collapse of 

water- or ice-rich target rocks 

Grooved, rugged, mound- or cone-shaped unit located at or near 

center of all impact craters with diameters ≥16 km. Circular to ovoid 

planimetric shape. Central pits common 

AHcp Crater peak unit

Crater rim unit

Nhc1

HNhc3

Nhc2

Hlu1

AHlu2

Htnv Htnf

AHc AHcea AHceb AHcr AHcw AHcf AHcp

Hephaestus Fossae

Phedra, Marbach, Tavua

Amenthes Cavi

reticulate ridges

Ehden, Canillo

Nepenthes Mensae

unnamed cavi

Cimmeria channels

Nepenthes Planum

Hephaestus Rupes

Tectonic extension

Impact

Mass wasting

Subsidence

Tectonic contraction Utopia Cimmeria ridges Cimmeria scarps

Linpu

CORRELATION OF MAP UNITS

Impact crater units

LOWLAND

PROVINCE

EARLY

AMAZONIAN

LATE

HESPERIAN

EARLY

HESPERIAN

LATE

NOACHIAN

MIDDLE

NOACHIAN

EARLY

NOACHIAN

HIGHLAND

PROVINCE

TRANSITIONAL

PROVINCE WIDELY OCCURRING EVENTS*

*Colors correspond to interpreted formational process (see text for summary). Dashed lines indicate uncertain temporal control.

Utopia region

units

Nepenthes region

units

Cimmeria region

units

QUADRANGLE LOCATION

Map showing the location of the Nepenthes Planum region (Mars Transverse 

Mercator (MTM) 10237, 10242, 10247, 15237, 15242, 15247, 20237, 20242, and 

20247 quadrangles; hachured region) and major physiographic features. 

Image is Mars Orbiter Laser Altimeter (MOLA) artificial hillshade overlain on 

a Thermal Emission Imaging System (THEMIS) daytime infrared (IR) mosaic. 

Orthographic projection centered at long 90° E.

0°

0° E 90° E

0°

180° E

30°

-30°

-60°

60°

30°

-30°

-60°

60°

VASTITAS BOREALIS

UTOPIA PLANITIA

ISIDIS

PLANITIA SYRTIS

MAJOR

PLANUM

HELLAS

PLANITIA

HESPERIA

PLANUM

TERRA

ARABIA

NOACHIS

TERRA

CIMMERIA

TERRA

TERRA

TYRRHENA

Elysium

Mons

E LY S I U M P L A N I T I A

N i l o s y r t i s M e n s a

e

N e p e n t h e s

M e n s a e

L i b y a M o n t e s

Prepared for the

National Aeronautics and Space Administration

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3389

Pamphlet accompanies map

Geologic Map of the Nepenthes Planum Region, Mars

By

James A. Skinner, Jr. and Kenneth L. Tanaka

2018

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

https://doi.org/10.3133/sim3389

Printed on recycled paper

Descriptions of nomenclature used on map are listed at 

http://planetarynames.wr.usgs.gov/

Elevations are based on topography derived from the Mars Orbiter 

Laser Altimeter (MOLA) experiment data set. For more information on 

the MOLA data, see Smith and others, 2001.

Any use of trade, product, or firm names in this publication is for descriptive purposes only 

and does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at https://doi.org/10.3133/sim3389

Suggested citation: Skinner, J.A., Jr., and Tanaka, K.L., 2018, Geologic map of the 

Nepenthes Planum Region, Mars: U.S. Geological Survey Scientific Investigations Map 

3389, pamphlet 11 p., scale 1:1,506,000, https://doi.org/10.3133/sim3389.

Prepared on behalf of the Planetary Science Division, Science

Mission Directorate, National Aeronautics and Space Administration

Edited by Scott D. Darling

Cartography by D. Paul Mathieux

Manuscript approved for publication November 16, 2017

150 75 0 150 KILOMETERS

SCALE 1:1 506 000 (1 mm=1.51 km)

TRANSVERSE MERCATOR PROJECTION

PLANETOCENTRIC LATITUDE AND EAST LONGITUDE COORDINATE SYSTEM