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Title: MICROBIAL MATS IN ANTARCTICA AS MODELS FOR THE SEARCH OF LIFE ON EUROPA


1
MICROBIAL MATS IN ANTARCTICA AS MODELS FOR THE
SEARCH OF LIFE ON EUROPA
  • Suman Dudeja
  • (Senior Lecturer)
  • A.R. S. D. College,South campus
  • University of Delhi
  • sdudeja.arsd_at_du.ac.in, dudejasuman_at_gmail.com

2
  • SUMAN DUDEJA
  • ARANYA B. BHATTACHERJEE
  • AND
  • JULIAN CHELA-FLORES
  • Associate ICTP
  • Max Planck Institute 
  • fur Physik Komplexer Systeme, 
    Nothnitzer Str. 38, 01187 Dresden,Germany
  • The Abdus Salam International Centre for
    Theoretical Physics, Trieste, Italy and Instituto
    de Estudios Avanzados, Caracas 1015A, Venezuela.
  • Permanent Institute Department of Physics and
    Chemistry, A.R.S.D College, University of Delhi,
    South Campus,
  • Dhaula Kuan, New Delhi-110021, India.

3
Out line of talk
  • Motivation
  • Life in extreme Environments
  • Microbial mats
  • Antarctica Sub glacial Lakes I/II
  • Europa and Laplace mission
  • Conclusions

4
Motivation
  • Observation of Europa by Galilean spacecraft.
  • Possibility of a warm ocean under the ice crust.
  • Possible existence of extra-terrestrial
    biological activity as Sulfur patches are found.
  • Anaerobes living in extreme environments found in
    sub glacial lakes in Antarctica.

5
Life In Extreme Environments
  • Extremophiles microorganisms not only tolerate
    harsh environments but thrive in them.
  • Examples
  • Thermophiles surviving in higher temp. till
    74-114ºC.
  • Psychrophiles are able to grow at -20ºC found in
    Antarctica
  • Halophiles tolerating salt concentration up to
    saturation.
  • Acidophiles live at pH as low as 0.5.
  • Alkalipihiles can survive till pH10-14.
  • Bacterium D. Radiourans can withstand ionizing
    radiations ( up to 20kGy of ?- radiation) and UV
    radiations (upto 1000Jm-2).
  • The Extreme environments and their microbes
    living in Mirobial Mats can thus act as models
    for extraterrestrial life.

Rothschild L. J. and Mancinelli R. L.(2001) Life
in extreme environments Nature,  409,  1092
Seckbach J., Oren A. and Chela-Flores, J. (sep
2008). European Planetary Science Congress in
Münster Germany. Seckbach, J. and Chela-Flores,
J. (2007)., in Hoover, R.B., Levin, G.V.,
Rozanov, A.Y. and Davies, P.C.W. (eds.),
Instruments, Methods, and Missions for
Astrobiology X. Proceedings of SPIE Vol. 6694,
66940W
6
Relevance of Microbial Mats in Astrobiology
7
Microbial mats on surface of some lakes
  • The mat has patches of white, yellow, and dark
    brown areascolonised by different groups of
    microorganisms, such as sulfur-oxidizers,
    sulfate-reducers, methanogens, and
  • other heterotrophs.  

What are sulfate reducers?
8
Sulfate Reducing Bacteria (SRB)as transport
agents
Under anaerobic conditions, sulfate is used by
bacteria as an electron acceptor for oxidation of
organic carbon by following reaction, called as
sulphate respiration or Dissimilatory bacterial
sulfate eduction, (SRB/BSR) 2ltCH2Ogt SO42-(aq) 
2H(aq) ? CO2(g)H2S(g) 2H2O (e- donor) The
isotope 32S increases in product H2S and thereby
reduced in SO42-. Presence of organic carbon
increases the rate of SRB. What is the source of
organic carbon? EPS (Exocellular Polymeric
Substance A metabolic product of microbes)
Biochemical sulfur cycle in a sedimentary
ecosystems with oxic/anoxic zones (Guerrero et.
al, 2002) thesis Alvarez (2005)
Jorgenson B. B. (1982a),. Nature, 296, 643-645
and (1982b),. Phill. Trans. R. Soc. Lond. B 298,
543-562. Rabus et al., (2006) The Prokaryotes,
Spinger, v2, p 659-768.
9
Antarcticas Subglacial Lakes and Mirobial Mats
  • Part-I
  • Perennially ice covered Lakes-Location
  • Dry valley Lakes/McMudro Lakes
  • Wright Valley/Victoria Valley/Taylor Valley lakes
  • Lake Boney/Lake Fryxel /Lake Chad// Lake Hoare
  • Lift-Off Microbial mats

10
Antarctica
11
Antarctica-Where are Dry Valleys?
How they are formed ?
12
McMudro Dry Valley Areas (Antarctica)
13
Taylor Valley Lakes Fly-over
14
Data of 4 of the 20 lakes of the McMurdo Dry
Valleys, Antarctica
__________________________________________________
__________________________________________________
________________
Lake Maximum depth, m Elevation, m ( above sea level) Lake type Microbial Mats
__________________________________________________
____________________
Lake Chad (Taylor Valley) 1.0 58 Perennial ice cover liquid water MM, ICM, FM, CLM, PRM
Lake Fryxell (Taylor Valley) 18 17 Perennial ice cover liquid water MM, ICM, FM, CLM, APRM, ANPRM
Lake Hoare (Taylor Valley) 34 73 Perennial ice cover liquid water, MM, ICM, FM, CLM, APRM, ANPRM
Lake Vanda (Wright Valley) 69 123 Perennial ice cover liquid water PM, APRM
__________________________________________________
__________________
15
Lake Hoare
Lake Hoare
                                              Lake Hoare from the North Shorewith Canada Glacier in the background
Lake Hoare
                                              Lake Hoare from the North Shorewith Canada Glacier in the background
from the North Shore
Lake Hoare Ice - 2005

                   
2006
Microbial mats in Lake Hoare (top view)
16
Antarctica's perennially ice-covered Lake Hoare
with sand and microbial mats (FM ICM) surface
down into the ice. Soil blows onto the lake from
a nearby dry valley, warms in the sun, and melts
downward, leaving a bubble column in its trail.
17
Estimated annual removal of selected chemical
constituents (Kg) by escaping algal mats in
lakes Chad, Hoare and Fryxell, Antarctica.

Chad Hoare Fryxell Organic
matter 8343.0 247.0 1450.0 Ca 279.5 105.9
552.1 Fe 352.3 76.6 309.5 S 104.0
56.0 40.1 Na 49.4 18.6 147.4 Cl 9.2
4.6 419.4 Parker et al. J. Phycol. Vol. 18,
72, (1982)
18
Benthic microbial mat community in Lake Hoare A
Bottom View
Underwater beneath the 4.5 meter thick ice-cover
of Lake Hoare, looking back at the dive hole.
.
19
Prostate microbial mats in lake Hoare at 8m
water depth
Pinacles (APRM) appearing (magnified)
Smooth-flattened (ANPRM)
Pinnacle mat (PM) morphology
20
Microbial Lift-Off (CLM)Mats in Antarctica dry
valley lakes
  • Benthic microbial mat in Lake Bonney. Gas buildup
    can cause mats tolift-off the bottom and
    sometimes tear loose and float up to the bottom
    of the ice cover in Antarctica dry valley lakes

SCUBA diver collecting sediment cores from Lake
Hoare in Taylor Valley.
21
Microbial community
Schematic representation of a cyanobacterial
microbial mat with associated depth-related
light and chemical gradients.
22
Antarctica-How dry valleys form?
Antarctica-Dry valley areas
  • Are the dry valley lakes microbial mats
    again present or in stage of evolution at
  • Lake Vostok ? and
  • may harbour life at Europa?

23
Antarcticas Subglacial Lakes Part-II
  • Lake Vostok
  • Location
  • Unexplored Lake beneath
  • 4km ice cover
  • Microbes found in 3.7km
  • Harboring hydrothermal vents

Nature Siegert et al., 2001, 414(6) 603 Jouzel
et al, 1999, Kapista et al., 1996, 381,
684, Priscu J. C. et al., Science, 1999, 286,
2141 Doran et. al., 1998
24
Antarctica subglacial lakes
Overview of Antarctica with Lake Vostok
25
Aerogeophysical data collected on a grid of
flight lines can be used to map Lake Vostok
The left image shows the ice surface.
On the right, you can
"see" through the ice. The image shows the
rocks outside the lake (brown colors) and the
lake surface beneath 4 km of ice (blue colors).
26
Digging across accreted (melted and refrozen) ice
in Lake Vostok
Mirobes found throughout 3.7km ice cover
of Lake Vostok
3540 m Interface
Environmental Microbiol., 3, 570-577, 2001
27
  • Thus, Lake Vostok
  • Appears to harbor hydrothermal vents beneath
    the water surface.
  • Geothermal heating will warm the bottom water.
  • Leading to vertical convective circulation in
    the lake
  • This warming of water appears to be responsible
    for supporting microbial growth in lake, as
    samples of accreted ice (melted and refrozen ice)
    are detected to contain many microbes.
    Proteobacteria having lineage to SRB
  • Suggestive of, what may be occurring on Europa
  • Ice cores drilled into ice of Antarctica exhibit
    the presence of mirobial life at all levels.
  • Shen Y. et. Al., Earth Sci. Rev., (2004) 64,
    342-272.

28
Overview of Jupiters Moon Europa Quick-Look
Statistics
Discovery Jan 7, 1610 by Galileo Galilei
NASAS missions Voyager (1975-76), Cassini
(2000), Galileo (1995-2003) Diameter (km) 3,138
Mean Distance from Jupiter (km) 670,900
Surface Composition Water Ice
29
Photos taken by the Galileo spacecraft, Nov 1998.
A small region of disrupted ice crust
False-color image reddish brown ridges and
terrain indicate the presence of contaminants in
the icy Europan surface
Double ridges, dark spots, and smooth icy plains
Greenberg R. Europa- The occean Moon, Springer
, 2005
30
Evidence of Mercaptans on Europa
Near Infra-red Mapping Spectrometer (NIMS)
Experiment by Galileo
3.88 micro-meter absorption line
Attributed to S-H bond of Mercaptans
T.B. McCord et. al., Jour. Geochem. Res. Vol.
103, N0. E4, pp. 8603 (1998).
31
EUROPAS CROSS SECTION
WATER
Silicate
Fe
ICE
32
How can an icy-moon EUROPA be habitable?
  1. Presence of liquid water ?
  2. Adequate energy source to sustain necessary
    metabolic reactions ?
  3. A source of chemical elements (C,N,H,P,O,S) ?
  4. Relevant pressure and temperature conditions ?
  1. Induced magnetic field measured by Galileo
    mission- PUTATIVE EXISTANCE OF OCEAN BENEATH ICE
    CRUST
  2. High level of radiation on Europa's surface may
    provide storage of chemical free energy SOURCE
    IN IRRADIATION PRODUCTS
  3. By recent models, liquid water is in contact with
    silicate core- FAVORABLE FOR PROVIDING VARIETY OF
    CHEMICALS
  4. Interactions in ocean and silicate core, can be
    the cause of HYDROTHERMAL ACTIVITY

Plot of biosignatures as a function of Depth
33
Laplace Resonance keeps the orbital periods of
IO, Europa and Ganeymade in the ratio of 124.
Orbital energy gained by IO due to tidal torques
exerted by Jupiter is distributed among 3 moons
locked in LR. This resonance is essential for
ongoing tidal heating inside Europa and may allow
for the existence of an ocean inside Europa over
billion of years.
34
The question of origin of Sulfur?
  • Ions implanted from the Jovian plasma.
  • Sulfurous material may be of geologic origin (
    Carlson et. al. Science, vol.286 (1999).
  • Accumulated effect of biogenic process over
    geologic time.

35
Parameters for biogenic Sulfur
  • Delta Sulfur parameter (d xS)
  • Isotope fractionation factor
  • Temperature

36
SIGNIFICANCE OF DELTA SULFUR (d xS) PARAMETER
Where, x  33, 34 or 36
Standard troilite of the Canon 
Diablo meteorite (CDM)
Metabolic  pathways of sulfur bacteria have enzyme
s that preferentially select  the  isotope 32S
 over 34S. This implies that where  there is an ab
undance of sulfur bacteria, the  value of  d34S 
would be negative.
37
Effect of Temperature
  • The magnitude of isotope fractionation xa ,
  • by microbial sulfate reduction also depends 
    upon temperature
  •  



Canfield D.E. , Olesen C.A. and  Cox R.P. (2006)
Temperature and its control of isotope
fractionation by a sulfate reducing bacterium,.
) Geochimica Cosmochimica Acta,  70, 548-561
38
Isotope fractionation as a function of temperature
39
SULFUR ION IMPLANTATION ON THE SURFACE OF EUROPA
  • Sulfur of biogenic origin if present on the
    surface of Europa is contaminated by energetic
    sulfur ions from Jovian atmosphere.
  • d34S value changes from its biological value due
    to contamination.
  • Future probe to Europa has to go beyond the 
    maximum stopping   depth of  the sulfur ions
  • (4.810-5cm)  to measure  d34S of biogenic
    origin.

40
Figure 2 Density distribution of sulphur ions n(x
) (atoms/cm3) implanted from the Jovian atmosphere
 as a function of dimensional depth (x/Rp)
for t  106 years , ? 9.0 106(cm 2 -s)-1 and
 Rp 4.8 10-5 cm.  The  maximum density is at th
e range x  Rp. The distribution is  Gaussian 
Graph based on the LSS(Lindhard, Scharff an
d Schiøt) theory of ion implantation
41
Major Questions
  • How biological processes would effect measurable
    and observable quantities?
  • What is the best way to detect them?
  • Drop penetrating probes and in situ Chemical
    and Physical laboratory (CPL).
  • Scan the surface for a window to the underlying
    ocean.

42
A proposed future mission for Jupiter and its
Moons
What should characterizemicro-penetrators
? Very low mass projectiles (c.f. Lunar A
13.5Kg DS-2 3.6Kg) High impact
speed Penetrate surface few metres Perform
initial important science on planetary surface
(2015-2025)
Blanc M. et al., Geopyical Research Abstracts,
vol10, EGU2008.
43
Europa Penetrators
  • Low mass projectiles 4KgPDS
  • High impact speed 200-500 m/s
  • Very tough 10-50kgee
  • Penetrate surface 0.5-few metres
  • Perform science from below surface

Low mass projectiles 4KgPDS High impact
speed 200-500 m/s Very tough
10-50kg Penetrate surface 0.5-few
metres Perform science from below surface
44
Conclusions
  • The experience with sub glacial lakes of
    Antarctica especially presence of Microbial mats
    at extreme environments is relevant for the
    exploration of the Solar system.
  • In the Solar System, Europa is the best candidate
    for the search of life outside the Earth.
  • Our calculations are in (IC/2008/34, and in
    Microbial Mats (Springer to be submitted by
    invitation)
  • These arguments suggest that with LAPLACE
    equipped with penetrators, only a penetration of
    a few millimeters would be sufficient for
    deciding on biogenicity.

45
AND SEARCH BEGINS
ALL TRUTHS ARE EASY TO UNDERSTAND ONCE THEY ARE
DISCOVERED THE POINT IS TO DISCOVER THEM -
GALILEO GALILEI
  • THANKS

dudejasuman_at_gmail.com , suman_dudeja_at_yahoo.co.in,

46
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47
  • Oceans verifying their existence, finding their
    locations, studying the structure of their icy
    crusts, and assessing active internal processes
  • Astrobiology determining the types of volatiles
    and organics on and near the surfaces, and the
    processes involved in their formation and
    modification
  • Jovian System Interactions studying the
    atmospheres of the satellites and the
    interactions among Jupiter and the surfaces and
    interiors of the satellites

48
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49
Effect of Temperature
  • The magnitude of isotope fractionation
    by microbial sulphate reduction also depends 
    upon temperature 



The isotope fractionation factor at equilibrium ca
n be derived from the ratios of the 
partition function (Q), 

50
The partition function is derived

Q  
Where, 
ui
h is the Planck constant, k is the Boltzman consta
nt, T is the temperature in Kelvin and 
 is the ?th vibrational frequency of the molecule)
 .
51
Based on the LSS(Lindhard, Scharff and Schiøt) the
ory of ion implantation, the implant profile in an
 amorphous material canbe described
by the equation (Sze, S. M.1988) 


(7) Where, 
Where, 


,
  is the implanted dose, t is the time of implanta
tion, Rp is the projection range and is equal to
the average distance an ion travels before it
stops and ?Rp is the standard deviation of Rp whic
h is roughly 1/5Rp from  the known  data  for 
different ions and impact surface. The value of Rp
 for sulfur ion for the Europan  surface  is
4.810-5cm  and  ? 9.0 106 (cm2 -s)-1
,
  
52
Graphs based on the LSS(Lindhard, Scharff and Schi
øt) theory of ion implantation
53
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