Astrobiology seeks to understand life in the context of the wider cosmos. Our own central conjecture is that life (and fossil life) is common in the solar system and exo-planetary systems – we research the evidence and mechanisms for transferring life between astronomical bodies, ie. panspermia.
to Royal Astro Soc. National Astronomy Meeting session
on Comets/Rosetta Mission, 6thJuly 2015. Publicised by the RAS at https://www.ras.org.uk/news-and-press/2654-do-micro-organisms-explain-features-on-comets
Icy structures and terrain in comet 67P
Max Wallisand N. Chandra Wickramasinghe
Despite the comet’s very black crust,
Rosetta’s remarkable images show several indicators of an underlying icy
morphology. Comet 67P displays smooth, planar ‘seas’ (the largest 600m X 800m) and flat-bottomed craters, both features seen also on comet
Tempel-1. Comet 67P’s surface is peppered with mega-boulders (10-70km)
like comet Hartley-2, while parallel furrowed terrain appears as a new ice
feature. The largest sea (‘Cheops’ Sea, 600 X 800m) curves around one
lobe of the 4km diameter comet, and the crater lakes extending to ~150m
across are re-frozen bodies of water overlain with organic-rich debris
(sublimation lag) of order 10 cm. The parallel furrows relate to flexing
of the asymmetric and spinning two-lobe body, which generates fractures in an
underlying body of ice. The mega-boulders are hypothesised to arise from bolide
impacts into ice. In the very low gravity, boulders ejected at a fraction
of 1m/s would readily reach ~100m from the impact crater and could land perched
on elevated surfaces. Where they stand proud, they indicate stronger
refrozen terrain or show that the surface they land on (and crush) sublimates
more quickly. Outgassing was already evident in September at 3.3AU, with
surface temperature peaks of 220-230K, which implies loosely bound H2O and/or unconsolidated organic mixtures.
Increasing rates of gassing as Rosetta follows comet 67P around its
1.3 AU perihelion will hopefully reveal the activation of possible
micro-organisms as well as the nature and prevalence of near-surface ices.
Wallis MK, Wickramasinghe NC (2015) Rosetta Images of Comet 67P/Churyumov–Gerasimenko: Inferences from Its Terrain and Structure. Astrobiol Outreach 3: 127. doi:10.4172/2332-2519.1000127 Open Access
Wickramasinghe NC, Wainwright M, Smith WE, Tokoro G, Al Mufti S, et al. (2015) Rosetta Studies of Comet 67P/Churyumov–Gerasimenko: Prospects for Establishing Cometary Biology. Astrobiol Outreach 3: 126. doi:10.4172/2332-2519.1000126 Open Access
Pioneer on martian meteorite biomorphs => Life-on-Mars
To a large
number in the scientific community, David McKay is best known as being the
point person in the Allan Hills 84001 (ALH84001) Life on Mars hypothesis. David was the lead author of the 1996 Science manuscript which jarred the
scientific community into reexamining our concepts about life on Mars. The paper was a team effort lead by David,
Everett Gibson and Kathie Thomas-Keprta.
The three team leaders and all of the other members of the team
(Christopher Romanek, Hojatollah Vali, Simon J. Clemett, Xavier D.F. Chillier,
Claud R. Maechling and Richard Zare) contributed to the hypothesis.
chain of evidence presented in the McKay et al. (1996) manuscript was believed
to be compatible with the existence of past life on Mars: (i) an igneous Mars
rock from (age around 4 to 4.5 Ga) which
had been penetrated by a low-temperature fluid along fractures and pore spaces,
which then became the sites for secondary mineral formations and possible
biogenic activity; (ii) a formation age for the carbonate globules (~3.9 Ga)
younger than the age of the igneous rock; (iii) SEM and TEM images of carbonate
globules and features resembling terrestrial microorganisms, terrestrial
biogenic carbonate structures, or microfossils; (iv) magnetite and iron sulfide
particles that could have resulted from oxidation and reduction reactions known
to be important in terrestrial microbial systems; and (v) the presence of
organic molecules associated with the carbonate globules. None of these
observations is in itself conclusive for the existence of past life. Although there are alternative explanations
for each of these phenomena taken individually, when they are considered
collectively, particularly in view of their spatial association, it provided
evidence for primitive life on early Mars (McKay et al., 1996). This paper has become one
of the most heavily cited papers in planetary science. With continued research, the team remains convinced
their evidence is solid and the best interpretation to explain these data is
that biogenic processes operated on early Mars.
McKay et al.
(1996) Search for past life on Mars: Possible relic biogenic activity in
Martian meteorite ALH84001, Science
Thomas-Keprta K.L., Clemett S.J., Gibson E.K. Jr., Spencer L. and Wentworth
S.J. (2009), Life on Mars: New evidence
from Martian meteorites. Proc. of SPI,, Instruments and Methods
for Astrobiology and Planetary Missions XII, Vol. 7441, 744102-1 to
733102-20 edited by R.B. Hoover, G.V. Levin, A.Y. Rozanov and K.D. Retherford. , San Diego, CA.
from Memorial tribute prepared by:
Gibson, Kathie Thomas-Keprta, Simon Clemett and Penny Morris-Smith
Research Office, NASA Johnson