Pascale Ehrenfreund


The 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 ice.
    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.

In 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 

  1. aliphatic and aromatic hydrocarbons (5-20 carbon atoms per molecule) 
  2. nitriles, ketones, aldehydes, organic acids 
  3. amino acids 
  4. polycyclic aromatic hydrocarbons (PAHs) (about 10-30 carbon atoms per molecule) 
  5. fullerenes C60, C70 and their hydrogenated or exohedral compounds 
  6. kerogens 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). 
This project 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.

Determining 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 chemical evolution. 

Principal Investigator:

Pascale Ehrenfreund 
Raymond and Beverly Sackler Laboratory for
Astrophysics at Leiden Observatory 
P O Box 9513 
2300 RA Leiden 
The Netherlands 
Tel: (31) 715275812 
Fax: (31) 715275819 


Bernard H. Foing 
European Space Agency, ESA, ESTEC, Noordwijk, The Netherlands 

Richard Ruiterkamp 
Leiden Observatory, Leiden, The Netherlands 

Elmar Jessberger 
Inst. für Planetologie, Westfälischen Wilhelms-Univ.Münster, Germany 

Max Bernstein 
NASA AMES RESEARCH Center, Mountainview, USA 

Luann Becker 
Hawaii Institute of Geophysics and Planetology, Honolulu, USA 

Guillermo Munoz 
Sackler Laboratory for Astrophysics, Leiden, The Netherlands 

Uwe Meierhenrich 
Univ. Bremen, Bremen, Germany 


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