Long-held theory of the Moon's magnetic crust debunked in study of past impacts

A new study of the Moon has offered scientists insights into why the Earth’s natural satellite’s crust is magnetized, ‘debunking’ one of two long-standing theories about the moon’s magnetic crust. The first is that the magnetization is the result of an ancient dynamo in the lunar core. The other is the result of an amplification of the interplanetary magnetic fields on meteoroid impacts. According to Australian researcher and study co-author Dr Katarina Miljkovic, from the Curtin University Space Science and Technology Centre, the research is a deep numerical study that challenges the second theory and essentially debunks it. “We found that meteoroid impact plasmas interact much more weakly with the Moon compared to the magnetization levels obtained from the lunar crust,” Miljkovic stated. He added that the findings led them to conclude that a core dynamo is the only plausible source of magnetization of the Moon’s crust. Dr Miljkovic provided the team with numerical estimates of the vapour formation that occurred during large meteoroid impact on the Moon some 4 billion years ago. During these impacts, the meteoroids hit the Moon at a very high speed, causing displacement, melting, and vaporization of the lunar crust. [caption id=“attachment_7458851” align=“alignnone” width=“1280”]  The study revealed regions on the Moon’s near side that have concentrations of radioactive elements unlike anywhere else on its surface that could explain its early stages of the moon’s formation.[/caption] The research calculated the mass and thermal energy of the vapour emitted during these impacts and then used them as an input for further calculations and investigation of the ambient magnetic field at the Moon. Lead author Dr Rona Oran stated that the impact simulations, combined with plasma simulations, harness the latest developments in scientific codes and computing power and allowed the team to perform the first simulations that could realistically capture and test this long-proposed mechanism. Dr Oran added that in addition to the Moon, Mercury, some meteorites and some other planetary bodies, all have magnetic crust. The scientist believes that the dynamo mechanism that is believed to have been in operation on the moon, could have been in effect there as well. The results of the study got published in the journal Science Advances.