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 

 

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 1

3 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)

Te

mp

era

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)

Vo

lum

e f

rac

tio

n o

f li

qu

id w

ate

r

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