The search for organic molecules and traces of life on Mars has been a major topic in planetary science for several decades. 26 years ago Viking, a mission dedicated to the search for life on Mars, detected no traces of life. The search for extinct or extant life on Mars is the future perspective of several missions to the red planet, for example Beagle 2, the lander of the Mars Express mission. In order to determine what those missions should be looking for, laboratory experiments under simulated Mars conditions are crucial. This review paper describes ongoing experiments that are being performed in support of future Mars spacecraft missions. Besides the description of the experiments, the experimental hardware and set-up, this paper also gives the scientific rationale behind those experiments. The historical background of the search for life on Mars is outlined, followed by a description of the Viking Lander biology and molecular analysis experiments and their results, as well as a summary of possible reasons why no organic compounds have been detected. A section concerning organic compounds in space and related experiments discusses the organic molecules we will use in simulation experiments. The set-up is discussed briefly in the following section. We conclude with an overview of future missions, stressing the relation between these missions and our laboratory experiments. The research described in this article has been developed as part of a Mars Express Recognized Cooperating Laboratory (RCL), and for planned future Mars missions such as the PASTEUR lander.