Geoscience Reference
In-Depth Information
8.5.1.2
Formaldehyde
In February 2005, it was announced that the Planetary Fourier Spectrometer (PFS)
on the European Space Agency's Mars Express Orbiter had detected traces of
formaldehyde in the atmosphere of Mars. Vittorio Formisano, the director of
the PFS, has speculated that the formaldehyde could be the by-product of the
oxidation of methane and, according to him, would provide evidence that Mars is
either extremely geologically active or harboring colonies of microbial life. NASA
scientists consider the preliminary findings well worth a follow-up but have also
rejected the claims of life.
8.5.1.3
Meteorites
NASA maintains a catalog of 34 Mars meteorites. These assets are highly valuable
since they are the only physical samples available of Mars. Studies conducted by
NASA's Johnson Space Center show that at least three of the meteorites contain
potential evidence of past life on Mars, in the form of microscopic structures resem-
bling fossilized bacteria (so-called biomorphs). Although the scientific evidence
collected is reliable, its interpretation varies. To date, none of the original lines
of scientific evidence for the hypothesis that the biomorphs are of exobiological
origin (the so-called biogenic hypothesis) have been either discredited or positively
ascribed to non-biological explanations.
In July 2014, it was published a paper with a new study co-funded by the NASA
Astrobiology Institute, where it is shown that the ribosomal RNA core - which
originated over 3 Gyrs ago before the Last Universal Common Ancestor (LUCA)
of life - is essentially the same in all living systems, throughout the evolution of
life on planet Earth (Petrov et al.
2014
). So if meteorites containing encapsulate
ribosomal RNA cores were ejected (by asteroidal/cometary impacts) from the Earth
to Mars, or vice versa, there is a possibility that such molecular structures (ribosomal
RNA, etc.) evolved into more complex biological molecules and, hypothetically,
into initial living cells on Earth and on Mars, in a panspermia scenario (de Morais
2004
).
Over the past few decades, seven criteria have been established for the recogni-
tion of past life within terrestrial geologic samples. Those criteria are:
1. Is the geologic context of the sample compatible with past life?
2. Is the age of the sample and its stratigraphic location compatible with possible
life?
3. Does the sample contain evidence of cellular morphology and colonies?
4. Is there any evidence of biominerals showing chemical or mineral disequilibria?
5. Is there any evidence of stable isotope patterns unique to biology?
6. Are there any organic biomarkers present?
7. Are the features indigenous to the sample?
Search WWH ::
Custom Search