Information Transmission via Molecular Communication in Astrobiological Environments

The ubiquity of information transmission via molecular communication between cells is comprehensively documented on Earth; this phenomenon might even have played a vital role in the origin(s) and early evolution of life. Motivated by these considerations, a simple model for molecular communication entailing the diffusion of signaling molecules from transmitter to receiver is elucidated. The channel capacity $C$ (maximal rate of information transmission) and an optimistic heuristic estimate of the actual information transmission rate $\mathcal{I}$ are derived for this communication system; the two quantities, especially the latter, are demonstrated to be broadly consistent with laboratory experiments and more sophisticated theoretical models. The channel capacity exhibits a potentially weak dependence on environmental parameters, whereas the actual information transmission rate may scale with the intercellular distance $d$ as $\mathcal{I} \propto d^{-4}$ and could vary substantially across settings. These two variables are roughly calculated for diverse astrobiological environments, ranging from Earth's upper oceans ($C \sim 3.1 \times 10^3$ bits/s; $\mathcal{I} \sim 4.7 \times 10^{-2}$ bits/s) and deep sea hydrothermal vents ($C \sim 4.2 \times 10^3$ bits/s; $\mathcal{I} \sim 1.2 \times 10^{-1}$ bits/s) to the hydrocarbon lakes and seas of Titan ($C \sim 3.8 \times 10^3$ bits/s; $\mathcal{I} \sim 2.6 \times 10^{-1}$ bits/s).