Animal migration associated with the Earth’s magnetic field has long been thought to be based on tiny magnetic particles. However, now it appears that there could be suitable chemical reactions that would do the trick. Peter J Hore and colleagues at Oxford University and Arizona State University have investigated the proposal that magnetically–sensitive free-radical reactions could be involved, in particular in the migration of birds.
The team has discovered that a carotenoid-porphyrin-fullerene system can respond to magnetic fields as weak as that of the Earth – around 50 μT. This is the first such system to be found. The idea is that light produces radicals, which can have their spins changed, via chemical effects, by an external magnetic field. The system investigated is probably a poor model for what might really happen in biological systems. Moreover, it can detect the weak magnetic field only at –150 °C. However, the result is a proof of principle and could lead to a new understanding of the magnetic senses of animals.