Post on 24-Feb-2016
description
Bacterial morphologies in carbonaceous meteorites and
comet dustChandra Wickramasinghe1, Max K. Wallis1, Carl H. Gibson2, Jamie Wallis1, Shirwan Al-
Mufti1 & Nori Miyake1
1 Cardiff Centre for Astrobiology, Cardiff University, UK.2 Depts of Mechanical and Aerospace Engineering and Scripps Institution of Oceanography, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla CA 92093-0411, USA
To re-visit evidence for microbial fossils in carbonaceous chondrites, linking with extensive modern evidence of Richard Hoover
Examine progress from Claus and Nagy, via Hans Pflug, to Richard Hoover and colleagues
To examine data for IDP’s in relation to embedded particles and organics
Discuss presence of acritarchs in cryosampler collections of cometary dust
Discuss relevance to cometary panspermia and cosmology
Aims
Early History of Microfossils Early in the 1960’s, Claus and Nagy
(1961) identified possible microfossils in carbonaceous chondrites (CCs), supported by chemical bio-markers
These were refuted vigorously on grounds of contamination and the subject fell into disrepute – some ragweed pollen but possibly small component
In the 1980’s the matter was re-opened by Hans Dieter Pflug using modern techniques
Pflug prepared ultra-thin sections (< 1mm) of the Murchison meteorite
H.D.Pflug•The sections were placed on membrane filters and exposed to hydrofluoric acid vapour.
• In situ demineralisation was achieved leaving carbonaceous structures indigenous to the meteorite in tact.
• A wealth of morphologies revealed.
Structures resembling the influenza virus
Laser ion probe showed biomarkers within the microfossils
Richard Hoover has found a wealth of microfossil structures with biomarkers + low N that leaves no room for dispute..
This is consistent with the distribution of biologically relevant molecules discovered in the Murchison meteorite by Schmidt-Koplin et al (2010)
If comets carriers of microbial life, a diversity of organic molecules as rich, or richer the terrestrial set is expected.
Water-ice and organics found in Tempel 13 areas less than 0.5% of surface, 1.5 & 2µm ice bands
Ice?
Ice could be surfaces of lakes exposed by im-pacts – and organics in plenty
Wavelength (m)
Normalised EmiissivityTempel-1 dust 9-12 micrometre bandEqual contributions to opacity by biologic grains and clay at peak99.51010.51111.51200.5
11.5Clay+biologic grains to aromatic ratio, z, at 11.2m
z=10:1z=1:1Data for Tempel 1+ Clay - evidence of liquid water in comets
Primordial radiogenic heating, with 26Al decays for comets forming 1My after incorporation of 26Al
Heat transfer calculations show melting for comets with radii in excess of 10km, with substantial volume fractions staying melted for periods of a fraction of My at least
Time (My)
Tem
pera
ture
(K)
0 1 2 3 4 50
100
200
300
400
500
600
INITIAL TEMPERATURE, 100KR = 30km, t = 1MyR = 20km, t = 1MyR = 15km, t = 1MyR = 10km, t = 1MyR = 8km, t = 1MyTime after melting (My)
Volu
me
frac
tion
of li
quid
wat
er
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60
0.1
0.2
0.3
0.4
0.5
0.6
R = 15km, t = 1MyR = 12km, t = 1MyPossibility of liquid water predicted theoretically
Conclusions so far...
Carbonaceous meteorites carry microfossils of living organisms
They are most likely relic comets that had liquid interior regions
Cometary pools sites for microbial replication?
Theories of cometary panspermia strongly supported by this data
Implication is that injection of microbes from comets is an ongoing process
Dust from modern comets
The Earth picks up debris from comets in the present day
Collection of comet dust in the atmosphere could provide additional proof of cometary life
Daily arrival rate 60 tonnes
Brownlee particles – collected from 1970’sAgglomeration of comet dust
18 micrometres
Similar to terrestrial fossil of iron-oxidising bacterium
Cyrosampler collections, from 2001 (ISRO)
Aseptic collection Low relative velocity preserves
fragile structures Searches for viable microbes + fossil
microbes possible Risk of contamination can be
minimised/avoided by going to sufficient heights
Stratospheric balloon with cryosampler probes launched from Hyderabad on 20
January 2001
•Each probe consists of a fully sterilised, evacuated stainless steel cylinder, of volume 0.35 litre•During flight the cylinders are immersed in liquid Ne, cooled to 25o K, thus producing a powerful cryopump.
•Over a hundred STP litres of air (and aerosols) in the height range 25-41 km is sucked in and frozen in situ
•When brought to ground level and room temperature, the air pressure ~ 200 bars•Collected air released through filters to trap aerosols
A wide range of particles from comets identified
Sizes from 0.1 – 10 µm
Mineral condensate mixed with carbonaceous material – possible nanobacteria, spores and fossil microbes C ~ 20%, O – 36%
Fe – 33%, low N+ Na + Ca + P
Acritarchs on Earth
Organic-walled microfossils found in sedimentary unidentified species
Present in sediments from 3.2Gy ago
Acritarchs in meteoritesRossignol-Strick + Barghoorn 1971 – revisited 2005 - acid macerated extract of the Orgueil CC meteorite- spherical hollow microstructures = well-defined walls
Mukhopadhyay, + SPIE 2009
Murchison SEM – part mineralised
Sulphur map
Achritarchs in cryoprobe sample2009About 9~10µm diam. spheres- Carbonaceous, often cracked, with cracks opening under the SEM heating
Lower image has fossilised flagella-whiskers
The carbon fraction ~ 60% also oxidised (O ~ 12%, N ~1%) Coating is mainly Na and Cl .. also some S, Si and K (< 1%)
Pair of 2.5-3 m acritarchs with intriguing coatings.
Very high C (58%)
Example of ~10m spherical particles + mineral coating
Very high in C (70%)
Consistently low N
Possible acritarchs occur abundantly in comet dust
collection
‘Grapes’ rich in C, O, Na, Fe and P.
Silicate whisker = 3 μm in length
‘CHO’ umbrella
+S1
+S2
S3+
Cracked shells and whiskers
Silica whiskers are abundantFirst thought to be contaminantNow found to be integral to acritarchs
Torroidal particles, with cracked shells
Diatoms most likely explanation
• Evidence of diatom silica in astronomical sources go back to work
of Hoover et al, 1984
Here the points are data for IR emission in the Trapezium nebula and the curve is for a mixed culture of diatoms
Only 10% mass from crystalline olivine is required
Diatom silica is consistent with comet spectraComet Hale-Bopp at 2.9 AU observed on 6-10-1996
Mix of olivine at temperature 175K and material resembling biomaterial including diatoms at 200K
We conclude with the intriguing possibility of living bacteria being included among the acritarchs
Samples are treated with carbocyanine dyes showing viable and dead cells.Viable (Green) and dead (Red) fluorescent stained bodies (bacteria) are obtained from air sampled at a height of 30-39km
Other bacteria detected by stains
Coccoidal forms in SEM – living bacteria
New work confirm thqt living bacteria are included in comet dust
More recently….
Concluding....
According to our favoured theory of cometary panspermia, living forms of the shapes we have seen were locked in frozen planets 10 million years after the Big Bang
The mass of each planet has a CNO content estimated to be ~ 1027 g.
The ingress of a single such planet into the pre-solar nebula provides material for 1011 Oort-cloud comets
Evidence of a disintegrating planet in the Helix Nebula provides striking evidence of such a process in action