Secondly, visual data was provided, which showed the high number of craters on the surface of the planet.[9] The visual data also allowed scientists to determine that Mercury had “not experienced significant crustal modification”.[10] This also added to the mystery of the magnetic field, as it was previously believed that the magnetic fields are caused by a molten dynamo effect, but since there was little crustal modification this undermined that idea. The visual data also allowed scientists to investigate the composition and age of the planet.[11]