The enigmatic beginnings of meteorites from Mars

In 1865, a 10-pound rock fell from space to Earth in the remote village of Sherghati, India. After more than a century of studying the meteorite fragments, researchers in the 1980s finally determined its alien origins: Mars. Until humans are able to bring back samples from Mars, the only pieces of the Red Planet found on Earth are Martian meteorites such as the shergottites. The journey for these little Martian travelers has been violent: for Mars rocks to get to Earth, they must have been ejected from the Red Planet’s surface with enough force to escape Martian gravity. This ejection was likely due to a large impact on Mars. The rocks withstood the massive temperatures and pressures of this impact and flew through the vacuum of space, eventually crash-landing on our own planet. For decades, scientists have worked on modeling the kind of Martian impact events that send bits of the Red Planet to Earth. Now, researchers at Caltech and the Jet Propulsion Laboratory (JPL) have conducted experiments to simulate the so-called “shock pressure” experienced by Martian rocks. They have found that the pressure required to launch a rock from Mars into space is much lower than originally thought.