The large-scale organization of chemical reaction networks in astrophysics

¹ ICREA-Complex Systems Lab, Universitat Pompeu Fabra (GRIB) Dr. Aiguader 80, Barcelona 08003, Spain
² Santa Fe Institute - 1399 Hyde Park Road, NM 87501, USA
³ Center of Astrobiology (NASA-associate) Ajalvir km 4, Torrejon de Ardoz, Madrid, Spain

Corresponding authors: ricard.sole@upf.edu andreea.munteanu@upf.edu

Received: 27 May 2004
Accepted: 31 August 2004

Abstract

The large-scale organization of complex networks, both natural and artificial, has shown the existence of highly heterogeneous patterns of organization. Such patterns typically involve scale-free degree distributions and small-world, modular architectures. One example is provided by chemical reaction networks, such as the metabolic pathways. The chemical reactions of the Earth's atmosphere have also been shown to give rise to a scale-free network. Here we present novel data analysis on the structure of several astrophysical networks including the chemistry of the planetary atmospheres and the interstellar medium. Our work reveals that Earth's atmosphere displays a hierarchical organization, close to the one observed in cellular webs. Instead, the other astrophysical reaction networks reveal a much simpler pattern consistent with an equilibrium state. The implications for large-scale regulation of the planetary dynamics are outlined.