Transcript attached - University of California, San Diego

Bacterial morphologies in
carbonaceous meteorites and comet
dust
Chandra 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
Aims





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
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 1
3 areas less than 0.5% of surface, 1.5 & 2µm ice bands
Ice?
Ice could be surfaces of
lakes exposed by impacts
– and organics in plenty
Tempel-1 dust 9-12 micrometre band
Equal contributions to opacity by biologic grains and clay at peak
1.5
Normalised Emiissivity
Clay+biologic grains to aromatic ratio, z, at 11.2m
z=10:1
z=1:1
Data for Tempel 1
+ Clay evidence of
liquid water
in comets
1
0.5
0
9
9.5
10
10.5
11
Wavelength (m)
11.5
12
Possibility of liquid water predicted theoretically
Primordial radiogenic heating, with 26Al decays for
comets forming 1My after incorporation of 26Al
600
0.6
Temperature (K)
400
Volume fraction of liquid water
INITIAL TEMPERATURE, 100K
R = 30km, t = 1My
R = 20km, t = 1My
R = 15km, t = 1My
R = 10km, t = 1My
R = 8km, t = 1My
500
300
200
100
R = 15km, t = 1My
R = 12km, t = 1My
0.5
0.4
0.3
0.2
0.1
0
0
0
1
2
3
Time (My)
4
5
0
0.2
0.4
0.6
0.8
1
1.2
Time afte r me lting (M y)
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
1.4
1.6
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’s
Agglomeration 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 meteorites
Rossignol-Strick + Barghoorn 1971 – revisited 2005
- acid macerated extract of the Orgueil CC meteorite
- spherical hollow microstructures = well-defined walls
Sulphur map
Murchison SEM – part mineralised
Mukhopadhyay, + SPIE 2009
Achritarchs in
cryoprobe sample2009
About 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 ~10m
spherical particles +
mineral coating
 Very high in C
(70%)
 Consistently low N
Possible acritarchs occur abundantly in
comet dust collection
S3
+
 ‘Grapes’ rich in C, O,
+
S2
Na, Fe and P.
+
S1
 Silicate whisker =
3 μm in length
 ‘CHO’ umbrella
Cracked shells and whiskers
Silica whiskers are abundant
First thought to be contaminant
Now 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
Diatom silica is consistent with comet spectra
Comet 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
Only 10% mass from crystalline olivine is required
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 presolar nebula provides material for 1011 Oortcloud comets
Evidence of a
disintegrating
planet in the
Helix Nebula
provides
striking
evidence of
such a process
in action