MIT Technology Review: In 2004 researchers found that the rate at which computer memories develop errors is directly related to the rate at which Earth is bombarded by high-energy neutrons, which are created when cosmic rays slam into the atmosphere. Now it appears that the rate of mutations in DNA may be similarly connected to that neutron bombardment. Augusto González of the Institute of Cybernetics, Mathematics and Physics in Havana, Cuba, studied data from a 26-year Escherichia coli experiment by Richard Lenski and coworkers at Michigan State University. In Lenski's experiment, 60 000 consecutive generations of E. coli were grown. Over a period of 20 000 generations, Lenski's team recorded about 300 million mutations, which equates to an average rate of 1 per second. González calculated that every 125 seconds a high-energy neutron would have entered the E. coli sample and transferred its energy to the water-like environment. Each neutron would have generated about 300 ions that radiate up to 100 nm, and another 30 ions that travel up to 0.1 mm. According to González, the rate at which those ions would collide with the bacteria correlates with the rate of the bacteria's mutation. However, he notes that further experimentation is necessary to reveal whether cosmic-ray neutrons are actually responsible for the mutation rate.
