Here we develop a plan to explore mud volcanoes near Acidalia Mensa with an MSL-class rover and propose a traverse based on geologic observations

Allen, C. C.

Oehler, D. Z.

Saper, L. M.

NASA Technical Reports Server

ROVER EXPLORATION OF ACIDALIA MENSA AND ACIDALIA PLANITIA: PROBING MUD 
VOLCANOES TO SAMPLE BURIED SEDIMENTS AND SEARCH FOR ANCIENT AND EXTANT LIFE  
L. M. Saper1, C. C. Allen2, D. Z. Oehler2. 1Brown University Dept. of Geological Sciences (lee_saper@brown.edu ), 
2Astromaterials Research and Exploration Science, NASA-JSC (carlton.c.allen@nasa.gov, doro-
thy.z.oehler@nasa.gov). 
 
      Here we develop a plan to explore mud volcanoes 
near Acidalia Mensa with an MSL-class rover and 
propose a traverse based on geologic observations. 
Introduction: 
      Bright pitted cones are common in the northern 
plains of Mars and have been documented to occur in 
numerous locations including Acidalia Planitia [1,2,3]. 
Various interpretations of these features have been 
proposed but growing consensus in recent literature 
has favored mud volcanism as the most likely forma-
tion mechanism [3,4,5,6,7]. Mud volcanoes are pro-
vocative targets for exploration because they bring to 
the surface sedimentary materials otherwise inaccessi-
ble by normal surface exploration [3,8] and can aid in 
reconstructing the sedimentary history of the northern 
plains. Also, by sampling fluids and sediments from 
deep in the Martian crust, mud volcanoes may be 
among the best places to search for ancient and extant  
life. 
Geologic Setting 
      The geologic history of Acidalia Planitia can be 
summarized in five stages (i) basin formed by a mega-
impact into early Noachian crust, (ii) volcanic resur-
facing by Hesperian ridged plains, (iii) deposition of 
sediments likely derived from outflow channels, (iv) 
formation of Vastitas Borealis (ABv), possibly by 
ocean sedimentation or as a sublimation lag from a 
frozen water body, (v) Amazonian resurfacing by 
obliquity-related periglacial processes [9,10,11]. The 
current surface of the planitia is dissected by kilometer 
scale polygon-forming troughs, bright pitted mounds 
and cones, and high concentrations of pedestal and 
rampart craters, all evidence of a volatile-rich subsur-
face history [7,12]. 
      Acidalia Mensa is an isolated massif and is one of 
the highest topographic landforms in the northern 
plains, exposing the oldest bedrock north of the di-
chotomy boundary [9]. The mensa is modified by 
troughs and fractures and is adjacent to a knobby colles 
indicating a volatile-rich history (Fig.1). 
Geologic Observations in Exploration Area 
      The oldest unit in the exploration area is inter-
preted to be Nepenthes Mensa (Nn), as mapped by [9, 
and is comprised of knobs and mesas that erode to 
aprons of high-albedo material. The unit is dissected 
by linear troughs that extend tens of kilometers and are 
several kilometers in width (Fig.1A, white arrows) 
[13]. 
      The next oldest unit is interpreted to be volcanic 
that appears to embay Nn, flowing into and filling 
troughs and craters and will not be accessed by the 
rover. 
      Dome and cone shaped high-albedo mounds occur 
south of the mesa and are interpreted to be mud volca-
noes. The mounds often express one to several muted 
central depressions or vents and occasionally are asso-
ciated with flow-like protrusions (Fig. 1B,C). The fea-
tures have a CRISM [14] visible spectral response best 
matching ferric oxide coatings, consistent with previ-
ous observations of similar mounds [3]. 
      The mounds are located within a low-albedo unit 
having concentric flow features with lobate margins 
and is interpreted to be younger than the mounds, al-
though evidence for the stratigraphic relationship re-
mains unclear. This unit contains circular to quasi-
circular features of that appear to be collapsed domes, 
possibly of relict mud volcanoes. The domes are up to 
6 km in diameter and are often associated with topog-
raphic highs and occasionally have mud-like flows 
protruding from their rims (Fig. 1D). 
      The youngest feature is a ray of ejecta and secon-
dary craters emanating from Bonestell Crater ~160 
kilometers to the southeast that superposes all other 
units. 
Table 1. Summary of exploration parameters. 
Name Acidalia Mensa 
Ellipse Center Lat/Long 44.58°N, 331.48°E 
Ellipse Elevation -4650 meters 
Launch Window Summer 2024 
EDL/Traverse Assume MSL capability 
Primary Science Targets 
(minimum distance from 
ellipse) 
Mud volcanoes (6km), 
Noachian Acidalia Mensa 
Scarp (3km) 
Landing Hazards Few sub-km craters (5% 
total area) 
Dust Cover Index ~0.9674 (low-med) 
Ellipse Slopes (10m) <1° to the South 
Rock Abundance Approx. ~1% 
Outstanding Questions to be Addressed in Exploration 
      (1) What is the nature of the supposed mud volca-
noes? Do they contain organics? What can they tell us 
about the sedimentary history of the northern plains? 
(2) How did Acidalia Mensa form? What was the role 
of volatiles? (3) What is the composition of the 
younger flow unit (mud or volcanic)? How does it re-
late to the mounds? What are the composition and ori-
gins of the collapsed domes? (4) How have tectonics 
shaped the Nepenthes Mensa unit and the formation of 
troughs on the mensa? (5) What is the nature of the 
https://ntrs.nasa.gov/search.jsp?R=20120002676 2019-08-30T19:20:12+00:00Z
Figure 1.  Background – MOLA DEM. Stretch is -5700m to -4000m. Inset (right) – CTX (P18_007889_2288_XI_48N023W, 
P17_007520_2267_XN_46N028W) mosaic showing proposed landing ellipse (red), nominal traverse (black), and context of explo-
ration area. White squares indicate locations of magnified insets: A – Bonestell secondaries, mensa scarp (white arrows), and first 
mud volcano (black arrow), B – Mound with extensive flow feature, C – well-formed mound with central edifice and vents, D – 
flow-like feature protruding from enigmatic annular raised-rim feature (B, C, D – HiRISE image ID ESP_018649_2250). 
interaction of ejecta rays and secondary craters with 
preexisting terrains? 
Exploration Plan: 
      A traverse has been formulated that would address 
the main science questions within two Martian years 
allowing time for winter ‘hibernation’ (Fig. 1). Upon 
arrival at each scientific target detailed measurements 
of bulk chemistry, mineralogy, grain size, and sedi-
mentary structures if applicable will provide geologic 
context and allow for correlation of materials among 
different locations along the traverse. A possible pay-
load of instruments would include a similar suite to 
MSL including color and hyperspectral imaging cam-
eras, a microscopic imaging camera (preferably with 
the ability to detect microfossils), mass and laser spec-
trometers, gas chromatograph, XRD/XRF, and rock 
abrasion tools. 
    Upon landing on the mensa the rover will assess its 
surroundings and perform chemical analyses to deter-
mine the composition and origin of the landing materi-
als. After ~75 days and 6 kilometers of traverse the 
rover will encounter the first science target – a string 
of secondaries from Bonestell superimposed on the 
landing materials. After a brief investigation of secon-
dary impact processes the rover will begin to descend 
off the mensa during which it can sample the scarp of 
the Nepenthes Mensa unit, looking for any sedimen-
tary structures and evidence of water. 
      At the base of the mensa the rover will and arrive 
at its first mud volcano (Fig. 1A) after a traverse of 
around 15 kilometers and 300 days of surface opera-
tions. Here the rover will perform detailed analyses of 
mound materials, possibly accessing the interior. If it is 
a mud volcano, the rover should administer the full-
suite of analyses on the matrix material as well as a 
collection of 5-10 different clasts. These analyses 
would include a search for organics in samples with 
the best preservation potential and analysis of aqueous 
indicators (hydrated minerals, structures). Next the 
rover would travel towards the largest flow feature 
after 22-km of traverse (Fig. 1B), taking time along the 
way to investigate the proposed collapsed domes. 
Similar analyses will be made at subsequent mud vol-
canoes, with attention to sedimentary structures and 
possible flow events. The rover will continue to trav-
erse over flow materials towards the mound that best 
represents similar features elsewhere on Mars (Fig. 
1C), at 27-km. Here the rover will attempt to drive to 
the central edifice of the mound to explore a potential 
vent. The final exploration target is a lobate structure 
emanating from collapsed dome feature (Fig. 1D). 
      Possible long-term targets include more mud vol-
canoes, isolated mesas and knobs in the plains (poten-
tially a ‘layered’ mesa to the west), more of the scarp 
of Acidalia Mensa, and a 
nearby gullied mesa. 
References: [1] Amador  ES et 
al. (2009) LPSC XLI, Abs. 1037, 
[2] McGowen EM (2011) Icarus, 
212, 622-628, [3] Oehler DZ, 
Allen CC (2010) Icarus, 20 8, 
636-657, [4] Skinner JA, Tanaka 
KL (2007) Icarus, 186, 41-59, [5] 
McGowen EM (2009) Icarus, 202, 
78-89, [6] Skinner JA, Mazzini A 
(2009) Marine & Petr. Geol., 26, 
1866-1878, [7] Farrand WH, et al. 
(2005) JGR, 110,  E05005:1-14, 
[8] Kopf AJ (2002) Rev. Geophys., 
40(2), 1005, [9] Tanaka KL (2005) 
Nature, 437, 991-994, [10] Oehler 
DZ, Allen CC (2010), LPSC XL, 
Abs. 1034  [11] Carr MH et al. 
(2010) EPSL, 294, 185-203 [12] 
Kadish SJ, et al. (2009) JGR, 114, 
E10001:1-25, [13] Martinez-
Alonso S, et al. (2011) Icarus, 
212, 596-621. [14] Murchie S, et 
al. (2007) JGR, 112, E05S03:1-57. 


Rover Exploration of Acidalia Mensa and Acidalia Planitia: Probing Mud Volcanoes to Sample Buried Sediments and Search for Ancient and Extant Life

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