New information about what is inside Mars shows the red planet has a molten liquid iron core, confirming the interior of the planet has some similarity to Earth and Venus. Researchers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., analyzing three years of radio tracking data from the Mars Global Surveyor spacecraft, concluded that Mars has not cooled to a completely solid iron core, rather its interior is made up of either a completely liquid iron core or a liquid outer core with a solid inner core. Their results are published in the March 7, 2003 online issue of the journal Science.