ABSTRACT
We wish to acknowledge the institutional support of the Centro de Astrobiologia. Special thanks to Prof. R. Lunar (Complutense University, Madrid), Prof. F. Rull (Valladolid University and CAB), Dr. A. Delgado (Estacion Experimental del Zaidin, Granada), Prof. L. Vazquez (Complutense University and CAB) and Dr. J. Gomez-Elvira (CAB). Also thanks to Prof. Dr. Sudhir Kumar Jain for his extremely kind invitation to write the present chapter, his constant help and editorial supervision. Finally, thanks to Dr. Andrew Hill for revision of the English version.
