Meteorites: rocky witnesses to the history of the formation of Earth and Mars

Rock samples from Earth and Mars are contemporary witnesses of planet formation. Their composition provides clues as to how both bodies became the planets we know today over the course of millions of years. New studies of the isotope ratios of the metals molybdenum, titanium, zirconium and zinc in Martian meteorites suggest that the building material of both planets originated largely from the inner solar system. In the final phase of their development, however, the two unequal neighbors must have evolved differently.