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@du. ac. in, dudejasuman@gmail. com
SUMAN DUDEJA# * ARANYA B. BHATTACHERJEE +* AND JULIAN CHELA-FLORES ** # Associate ICTP + Max Planck Institute f¨ur Physik Komplexer Systeme, N¨othnitzer Str. 38, 01187 Dresden, Germany ** The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy and Instituto de Estudios Avanzados, Caracas 1015 A, Venezuela. * Permanent Institute: Department of Physics and Chemistry, A. R. S. D College, University of Delhi, South Campus, Dhaula Kuan, New Delhi-110021, India.
Out line of talk • • Motivation Life in extreme Environments Microbial mats Antarctica Sub glacial Lakes I/II • Europa and Laplace mission • Conclusions
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.
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 p. H as low as 0. 5. – Alkalipihiles can survive till p. H 10 -14. – Bacterium D. Radiourans can withstand ionizing radiations ( up to 20 k. Gy of γ- radiation) and UV radiations (upto 1000 Jm-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, 66940 W
Relevance of Microbial Mats in Astrobiology
Microbial mats on surface of some lakes • The mat has patches of white, yellow, and dark brown areas: colonised by different groups of microorganisms, such as sulfur-oxidizers, sulfate-reducers, methanogens, and other heterotrophs. What are sulfate reducers?
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) 2<CH 2 O> +SO 42 -(aq) + 2 H+(aq) CO 2(g)+H 2 S(g) +2 H 2 O (e- donor) The isotope 32 S increases in product H 2 S and thereby reduced in SO 42 -. 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) Jorgenson B. B. (1982 a), . Nature, 296, 643 -645 and (1982 b), . Phill. Trans. R. Soc. Lond. B 298, 543 -562. Rabus et al. , (2006) The Prokaryotes, Spinger, v: 2, p 659768. Biochemical sulfur cycle in a sedimentary ecosystems with oxic/anoxic zones (Guerrero et. al, 2002); thesis Alvarez (2005)
Antarctica’s Subglacial Lakes and Mirobial Mats Part-I • Perennially ice covered Lakes-Location – Dry valley Lakes/Mc. Mudro Lakes • Wright Valley/Victoria Valley/Taylor Valley lakes – Lake Boney/Lake Fryxel /Lake Chad// Lake Hoare • Lift-Off Microbial mats
Antarctica
Antarctica-Where are Dry Valleys? How they are formed ?
Mc. Mudro Dry Valley Areas (Antarctica)
Taylor Valley Lakes Fly-over
Data of 4 of the 20 lakes of the Mc. Murdo Dry Valleys, Antarctica __________________________________________________________ Maximum depth, m Lake Elevation, m ( above sea level) Lake type & Microbial Mats ___________________________________ Lake Chad (Taylor Valley) 1. 0 Lake Fryxell (Taylor Valley) 18 Lake Hoare (Taylor Valley) 34 58 Perennial ice cover; liquid water; MM, ICM, FM, CLM, PRM 17 Perennial ice cover; liquid water; MM, ICM, FM, CLM, APRM, ANPRM 73 Perennial ice cover; liquid water, MM, ICM, FM, CLM, APRM, ANPRM CLM 69 123 Perennial ice cover; liquid Lake Vanda water; PM, (Wright Valley)__________________________________ APRM
from the North Shore Lake Hoare Ice - 2005 2006 Microbial mats in Lake Hoare (top view) Lake Hoare L a
Antarctica's perennially ice-covered Lake Hoare with sand 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.
Estimated annual removal of selected chemical constituents (Kg) by escaping algal mats in lakes Chad, Hoare and Fryxell, Antarctica. Chad Organic matter 8343. 0 Ca 279. 5 Fe 352. 3 S 104. 0 Na 49. 4 Cl 9. 2 Hoare Fryxell 247. 0 105. 9 76. 6 1450. 0 552. 1 309. 5 56. 0 18. 6 4. 6 Parker et al. J. Phycol. Vol. 18, 72, (1982) 40. 1 147. 4 419. 4
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.
Prostate microbial mats in lake Hoare at ~8 m water depth Smooth-flattened (ANPRM) Pinacles (APRM) appearing (magnified) Pinnacle mat (PM) morphology
Microbial Lift-Off (CLM)Mats in Antarctica dry valley lakes • Benthic microbial mat in Lake Bonney. Gas buildup can cause mats to lift-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.
Microbial community Schematic representation of a cyanobacterial microbial mat with associated depth-related light and chemical gradients.
Antarctica-How dry valleys form? Antarctica-Dry valley areas v Are the dry valley lakes microbial mats again present or in stage of evolution at Lake Vostok ? and v may harbour life at Europa?
Antarctica’s Subglacial Lakes Part-II Lake Vostok – Location – Unexplored Lake beneath 4 km ice cover: Microbes found in ~3. 7 km – 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
Overview of Antarctica with Lake Vostok Antarctica subglacial lakes
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).
Digging across accreted (melted and refrozen) ice in Lake Vostok Mirobes found throughout ~3. 7 km ice cover of Lake Vostok ~3540 m Interface Environmental Microbiol. , 3, 570 -577, 2001
Thus, Lake Vostok Ø Appears to harbor hydrothermal vents beneath the water surface. Ø Geothermal heating will warm the bottom water. Ø Leading to vertical convective circulation in the lake Ø 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* ØSuggestive of, what may be occurring on Europa Ø 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.
Overview of Jupiter’s Moon Europa & Quick-Look Statistics Discovery: Jan 7, 1610 by Galileo Galilei NASA’S missions: Voyager (1975 -76), Cassini (2000), Galileo (1995 -2003) Diameter (km): 3, 138 Mean Distance from Jupiter (km): 670, 900 Surface Composition : Water Ice
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
T. B. Mc. Cord et. al. , Jour. Geochem. Res. Vol. 103, N 0. E 4, pp. 8603 (1998).
EUROPA’S CROSS SECTION WATER Silicate Fe ICE
How can an icy-moon EUROPA be habitable? 1. 2. 3. 4. 1. 2. 3. 4. Presence of liquid water ? Adequate energy source to sustain necessary metabolic reactions ? A source of chemical elements (C, N, H, P, O, S) ? Relevant pressure and temperature conditions ? Induced magnetic field measured by Galileo mission- PUTATIVE EXISTANCE OF OCEAN BENEATH ICE CRUST High level of radiation on Europa's surface may provide storage of chemical free energy SOURCE IN IRRADIATION PRODUCTS By recent models, liquid water is in contact with silicate core- FAVORABLE FOR PROVIDING VARIETY OF CHEMICALS Interactions in ocean and silicate core, can be the cause of HYDROTHERMAL ACTIVITY Plot of biosignatures as a function of Depth
Laplace Resonance: keeps the orbital periods of IO, Europa and Ganeymade in the ratio of 1: 2: 4. 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.
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.
Parameters for biogenic Sulfur • Delta Sulfur parameter (δ x. S) • Isotope fractionation factor • Temperature
SIGNIFICANCE OF DELTA SULFUR (δ x. S) PARAMETER Where, x = 33, 34 or 36 Standard: troilite of the Ca˜non Diablo meteorite (CDM) Metabolic pathways of sulfur bacteria have enzymes that preferentially select the isotope 32 S over 34 S. This implies that where there is an abundance of sulfur bacteria, the value of δ 34 S would be negative.
Effect of Temperature The magnitude of isotope fractionation ‘xα’ , 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
Isotope fractionation as a function of temperature
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. • δ 34 S 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. 8× 10 -5 cm) to measure δ 34 S of biogenic origin. S of biogenic origin
F i g u r e 2 : D e n s i t y d i s t r i b u t i o n o f s u l p h u r i o n s n ( x) ( a t o m s / c m 3 ) implanted from the Jovian atmosphere as a function of dimensional depth (x/Rp) f o r t = 1 06 y e a r s , ф = 9. 0 × 1 06 (c m 2 - s )- 1 a n d R p = 4. 8 × 1 0 - 5 c m. The maximum density is at the range x = Rp. The distribution is Gaussian Graph based on the LSS(Lindhard, Scharff and Schiøt) theory of ion implantation
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.
A proposed future mission for Jupiter and its Moons What should characterize micro-penetrators ? Very low mass projectiles (2015 -2025) (c. f. Lunar A 13. 5 Kg; DS-2 3. 6 Kg) High impact speed Penetrate surface ~ few metres Perform initial important science on planetary surface Blanc M. et al. , Geopyical Research Abstracts, vol: 10, EGU 2008.
Europa Penetrators Detachable Propulsion Stage – Low mass projectiles Low mass ~4 Kg+PDS projectiles Point of Separation ~4 Kg+PDS – High impact speed ~ 200 -500 m/s High impact speed ~ 200 -500 m/s – Very tough Payload Instruments ~10 -50 kgee Very tough – Penetrate surface ~10 -50 kg ~0. 5 -few metres Penetrate surface – Perform science ~0. 5 -few metres from below surface Perform science from below surface Penetrator PDS (Penetrator Delivery System)
Conclusions n 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. n In the Solar System, Europa is the best candidate for the search of life outside the Earth. n Our calculations are in (IC/2008/34, and in “Microbial Mats” (Springer to be submitted by invitation) n These arguments suggest that with LAPLACE equipped with penetrators, only a penetration of a few millimeters would be sufficient for deciding on biogenicity.
AND SEARCH BEGINS “ALL TRUTHS ARE EASY TO UNDERSTAND ONCE THEY ARE DISCOVERED; THE POINT IS TO DISCOVER THEM” - GALILEO GALILEI THANKS dudejasuman@gmail. com , suman_dudeja@yahoo. co. in,
• 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
Effect of Temperature The magnitude of isotope fractionation by microbial sulphate reduction also depends upon temperature The isotope fractionation factor at equilibrium can be derived from the ratios of the partition function (Q), =
The partition function is derived Q = Where, ui= h is the Planck constant, k is the Boltzman constant, T is the temperature in Kelvin and is the ίth vibrational frequency of the molecule).
Based on the LSS(Lindhard, Scharff and Schiøt) theory of ion implantation, the implant profile in an amorphous material canbe described by the equation (Sze, S. M. 1988): Where, = , is the implanted dose, t is the time of implantation, Rp is the projection range and is equal to the average distance an ion travels before it stops and ΔRp is the standard deviation of Rp which is roughly 1/5 Rp from the known data for different ions and impact surface. The value of Rp for sulfur ion for the Europan surface is : 4. 8× 10 -5 cm and ф =9. 0× 106 (cm 2 -s)-1
Graphs based on the LSS(Lindhard, Scharff and Schiøt) theory of ion implantation
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