Analogue Sites for Mars Missions (2011)
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The Cuatro Cienegas Basin in Coahuila, Mexico: An Astrobiological Precambrian Park
and Mars Analogue
V. Souza1*, J. Siefert2, J. J. Elser3 and L. E. Eguiarte1.
1
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional
Autónoma de México, AP 70-275, CP 04510, Mexico DF. Mexico. 2Department of
Statistics, Rice University, Houston Texas, USA. 3School of Life Sciences, Arizona
State University, Tempe, Arizona, USA.
Introduction: The candidate mission MSL 2018 has targeted four landing sites.One of
them, Gale crater appears to have
recorded a diverse stratigraphy in a well
defined mound that may likely reflect
deposition during dynamic environmental
conditions. Additionally, it has been
postulated that biosignatures may be
preserved in the sulfate bearing strata in
the mound. Herein we describe the
parallel ecological parameters and the
astrobiological research at our site that
make the environmental phenomenon of
Gale crater the most analogous MLS
target to Cuatro Cienegas Basin.
The Cuatro Cienegas Basin (CCB) is an oasis in the Chihuahuan desert in the
state of Coahuila in the North of Mexico. Despite the arid climate, the CCB harbors an
extensive system of springs, streams, and pools of significant scientific interest. It
presents an extreme elemental stoichiometry with regards to phosphorus, (900:150:115820:157:1 C:N:P ratio) 1, 9 when compared to similar environments. Its spring-fed
ecosystems are dominated by microbial mats and living stromatolitic features (see
figure 1) supported by an aquatic sulfur cycle and a terrestrial gypsum based ecology in
large parts of the valley1. Our work there indicates that the microbial lineages of the site
carry a signature of an ancient marine ancestry in their genomes2-8 and understanding
the link between this signal and the palogeochemistry of the oasis is a current focus of
our research. These unique biosignatures, the abundance of fossil and living
microbialites, the geologic history, and the biodiversity make CCB interesting for
Astrobiology. Moreover, molecular clock studies on the genomes of Bacillus and
Exiguobacteria as well as Cyanboacteria from CCB demonstrate that many species
from Cuatro Cienégas have diverged from related true marine species in the late
Proterozoic.7, 8 It is our inference that CCB represents an extant ecological “time
machine” suggestive of earlier times in Earth’s history and by extension, other similar
Analogue Sites for Mars Missions (2011)
extraterrestrial planet bodies during their
paleoecological past. One of the primary research
concerns of the CCB team is to understand in broad
terms how microbial life colonizes, adapts and
diversifies. Our ultimate goal is to use CCB to
provide empirically generated rules of microbial
evolution that can be extrapolated to alternative
ecologies. As results are tallied, we are continually
refining our system of rules of ‘coexistence’ in the
bacterial communities of CCB. Special attention is
given to descriptive and chemical biosignatures that
are evidenced by the adaptive response to the
geologic environment.
The ability to extrapolate, even in first order
terms, the adaptive potential of earth based
microbial life provides a platform on which to
consider the profoundly different evolutionary
trajectory from Earth to sister planets such as Mars.
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Table 1
Site Name
CUATRO
CIENEGAS
COAHUILA
Center Coordinate
26°59′N 102°03′W
Elevation
740 masl
Areal Extent
40 km by 30 km
Prime Science
Questions
How early life on
Earth survived,
diversified and
changed the destiny
of the planet?
Distance to road
4 km.
Environmental
characteristics
Max temp:55 C
Min temp: -2 C
Precipitation: 150
mm
Vegetation
coverage:30%
gypsophylic shrubs,
and halophyle grass
Mission Description: Gale crater as a primary MSL
target has been chosen due to the mound and moat
Previous studies
10 years of
preservation and the accompanying stratigraphy that at analogue site
research and 15
publications
indicates the fluvial system was supplied by
underground hydrologic sources. All of these
Primary Landing
Gale crater(17)
considerations can be informed by the CCB
Site Target
analogue site presented herein. A more far ranging
Other
Any other items of
goal of the MSL and subsequent sampling initiatives
interest
involve the exploration to determine the presence,
precedent, or absence of microbial life as Gale crater and the efforts at CCB are easily
extrapolated to provide an exploratory platform for this discovery.
Science Merit Related to Mission Objectives: The CCB presents a dynamic
hydrologic system. Over roughly 11,000 years, the oasis valley floor records waxing and
waning of many spring fed pool systems, as well as multiple sites where evaporative
systems have come and gone. Additionally, a more ancient geologic history indicates
that CCB was at the very nexus of the breaking apart of Pangea that created what we
now know as the Northern hemisphere 220 million years ago. Much later CCB became
isolated from the sea with the subsequent uplifting of the Sierra Madre Oriental, roughly
~35 million years ago.11 It is possible that the CCB was not “buried” by the normal
succession of new sediments and this in turn suggests that the ancient microbial mats
may have survived these changes as they became isolated from their original marine
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source. 2, 12, 13 Therefore in the MSL/Mars 2018 mission it should be possible to view the
Gale crater candidate landing site as more similar to CCB with regards to the dynamics
of the geology. We propose that there may be sites similar to CCB where evaporitic
processes might indicate the presence of past water and where it would be feasible to
look for evidences of rudimentary microbial mats, i.e., banded structures with isotopic
anomalies.
Most Important Question Answered by Site: CCB provides a living laboratory in
which a diverse group of scientists have the opportunity to understand microbial
evolution in concert with its environment. The ability to directly and empirically evaluate
these processes provides the definition for rules and adaptation of earth based
microbial populations and provides a definition and estimation of the veracity for
biosignatures extra terrestrially. These biosignatures are part of a much larger
astrobiological definition effort involving the Virtual Planet Laboratory at U Washington
and the ASU Follow the Elements team. Interestingly, the success of the collaborative
efforts at CCB by geochemists, geologists, ecologists, and population biologists directly
impacts the team’s ability to interact with mission specialists in a way that makes
crossing disciplinary boundaries and impacting mission outcomes in a positive way.
Logistic and Environmental Constraints: CCB is in the center of the Chihuahuan
desert and can be accessed by several routes using international air carriers and land
vehicles. Transportation involves air carrier to Monterrey or Saltillo. Overland vehicles
complete the route to CCB in 4.5 hours from both airports. Travel directly from Houston
through Piedras Negras (Coah, Mx) can be accomplished in roughly 10 hours. The
charming town has a population of 10,000 people, has hotels, restaurants and modern
amenities such as reliable cell phone connection and WiFi. The field sites are 30km in
average from the town. CCB has similar weather as Phoenix. The Mexican team has all
the collecting permits in order and has extended its permits to the international
collaborators without problem.
References
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Microbiol. 11, 16-34.[7] Moreno-Letelier, et al. (2011) International Journal of Evolutionary Biology on line.
[8] Domínguez-Escobar (2011). FEMS Microbiology Letters, on line.[9] Peimbert, M in corrections to be
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Jackson, S. (2008) Journal of Biogeography 35: 188-190[13] Wilson J. S and Pitts J. P. (2010). Progress
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