Iron is known to occur in four different crystal structural forms. One of these, the densest form (epsilon phase, hexagonal close-packed) is considered to have formed Earth's core. Theoretical arguments based on available high-temperature and high-pressure iron data indicate the possibility of a fifth less dense iron phase forming the core. Study of iron phase transition conducted between pressures of 20 to 100 gigapascals and 1000 to 2200 Kelvin provides an experimental confirmation of the existence of this new phase. Thee epsilon iron phase transforms to this lower density phase before melting. The new phase may form a large part of Earth's core.