Deep-mantle garnet majorite explains Mars' oxidized rocks

Researchers at Ehime University found that majorite, a garnet forming at about 18 GPa near the base of Mars' mantle, traps oxidized ferric iron in its crystal structure. This resolves why Martian meteorites appear highly oxidized despite forming in a reducing environment.

• Majorite forms at about 18 GPa and 2150–2200 °C
• 11% to 21% of iron in majorite crystals was oxidized
• Experiments used a hydraulic press; analysis was done at the SPring-8 synchrotron
• Findings also apply to Earth's mantle transition zone where bridgmanite turns into majorite