About half of the heat emanating from the bowels of the Earth, left over from the formation of planets. Such a conclusion is made by scientists, the article is published in the journalNature Geoscience. Full article available here, and briefly on writes portal ScienceNOW.
Land, which was formed as the other planets in the solar system, from a single cloud of gas and dust about 4.5 billion years ago, all the time from now on is hot. Planet receives heat from two main sources: the first — the decay of radioactive elements in the Earth's interior (uranium and thorium), and the second — it's warm, left over from the time of formation of the planet.
The authors evaluated a new job, what is the contribution of each of these two sources, studying antineutrinos, which are created by the decay of radioactive elements. The researchers analyzed data collected from KamLAND neutrino detector on the island of Honshu in Japan. Neutrino — is very light elementary particles that are involved in only two of the four fundamental interactions — weak, and gravitational. Neutrinos interact very weakly with other types of substances, so they are difficult to detect.
In the period from March 2002 to November 2009, KamLAND detector registered 841 cases of generation neutrino. The source of 485 of them were nuclear reactors and nuclear waste disposal, and another 245 were formed by the collision of cosmic rays with the gas molecules in the Earth's atmosphere. Of the remaining 111 cases were born five neutrino questionable, so scientists have concluded that radioactive decay is given only 106 events of formation of these elementary particles.
Given how poorly neutrinos interact with other types of matter, from the data, scientists have determined the approximate intensity of their education in the bowels of the planet. According to their estimates, every second through a square centimeter of the Earth's surface is 4.3 million neutrinos. From these data, scientists have calculated the approximate intensity of the processes of decay and the number of generated heat — it was approximately equal to 20 terawatts. Decay of radioactive calcium additionally provides for about 4 TWh. Together, these processes provide about 54 percent of the total coming from the Earth's interior heat. Accordingly, the rest remained warm since the formation of the planet.
In earlier works were received about the same evaluation, but so far experts have relied not on the study of processes occurring inside the planet, and on the analysis of the composition of meteorites, also formed about 4.5 billion years ago.