ORGANICS ON MARS
first spacecraft to visit Mars was Mariner 4 in 1965, which was followed
by Mars 2 (the first spacecraft to land on Mars) and the two Viking landers
in 1976. The search for evidence of extant or past life on Mars has so
far only produced inconclusive results (Klein 1992). No definitive evidence
for or against extant Martian life was provided by biological experiments
on the Viking lander.
The atmosphere of Mars today is composed chiefly of carbon dioxide (95.3
%), nitrogen (2.7 %) and argon (1.6 %). The atmospheric pressure is less
than 1/100th that of Earth. The current Mars environment is too cold (and
the atmosphere is too thin) to retain liquid water on its surface. However,
data from the Mars Pathfinder, which landed successfully on Mars in July
1997, suggested widespread flowing water in the previous history of Mars.
Water, an important ingredient for life, could also be trapped as underground
The past conditions of Mars may have eventually allowed life to develop.
However today, a combination of solar ultraviolet radiation, the extreme
dryness of the soil, and the oxidizing nature of the soil chemistry prevent
the formation of living organisms in the Martian soil.
Current and future Mars missions are searching for past and present life
with the help of instruments which can identify tracers for life, namely
organic molecules and fossils, hidden in rocks and in the Martian subsurface.
Whereas the detection of macromolecular kerogens and fossils would indicate
a biotic origin and represent an indication for life, other organic compounds,
such as PAHs, fullerenes, aliphatic chains, and others may be abiotic in
origin and be delivered by small bodies.
preparation for the EMF (Exobiology
Multi-User Facility) proposed for a MARS 2005 Lander (described in
the ESA Exobiology Science Team Study, 1998) in response to ESA-AO-LS-99,
this experiment will study the stability and evolution of organic molecules
on the Martian surface and their implications for extinct and extant life
on Mars. Various organics, embedded in Martian soil analogs, will be exposed
to simulated Martian atmospheres, UV radiation and oxidyzing agents. Among
the tested sustances are
will be undertaken with the support of the European
Space Agency ESA, by using a refurbished and equipped vacuum chamber.
Our knowledge on how biological processes would develop on Mars and if
life forms would form in the same way as on Earth is rather limited. This
experiment is dedicated to investigate the cycle of abundant organic molecules
identified in solar-system bodies and beyond, which may have been exogenously
delivered to the Martian surface. Early Earth and Mars may have been seeded
with organic material from meteorites and comets which have survived the
impact. Such molecules may have been destroyed, altered or displaced into
deeper soil layers, where they are protected from radiation and oxidation.
and aromatic hydrocarbons (5-20 carbon atoms per molecule)
ketones, aldehydes, organic acids
aromatic hydrocarbons (PAHs) (about 10-30 carbon atoms per molecule)
C60, C70 and their hydrogenated or exohedral compounds
and bitumens: complex organic mixtures (100.000 amu) of 3-dimensional networks
of aromatic and aliphatic structure, including a variety of heteroatoms
(also a reference material for meteorites).
the most likely distribution of meteoritic and cometary organic molecules
that could seed primitive planets is a key astrobiological objective since
it sets the initial conditions for at least part of their phase of prebiotic
and Beverly Sackler Laboratory for
at Leiden Observatory
O Box 9513
Space Agency, ESA, ESTEC, Noordwijk, The Netherlands
Observatory, Leiden, The Netherlands
für Planetologie, Westfälischen Wilhelms-Univ.Münster, Germany
AMES RESEARCH Center, Mountainview, USA
Institute of Geophysics and Planetology, Honolulu, USA
Laboratory for Astrophysics, Leiden, The Netherlands
Bremen, Bremen, Germany