... SUN MOON MERCURY VENUS MARS, JUPITER SATURN . ... Observing . ... Supernova showered Earth with radioactive debris . ... Earth and Mars distinct to the core . New research uses silicon isotopes to distinguish between the formation of Earth's core and that of Mars. ... With Earth being eight times larger than Mars, the pressure of core formation could be higher, and different silicate phases may have been involved. ... Only registered members of Astronomy.com are allowed to comment on this article. ...