How Martian meteorites crash-land on Earth? New study simulates impact

Martian meteorites such as the Shergottites are the only pieces of the Red Planet found on Earth. Over the years, scientists have dedicated considerable effort to understanding the impact events that propel these Martian rocks into space and eventually on Earth.

Recently, a team of researchers from Caltech and NASA's Jet Propulsion Laboratory (JPL) conducted groundbreaking experiments to replicate the "shock pressure" experienced by Martian rocks on Mars and found that the pressure required to launch a rock from Mars into space is much lower than originally thought.

The team, led by Caltech staff scientist Jinping Hu, conducted experiments to smash rocks containing plagioclase - a major component of Martian rocks - from Earth and observe how the mineral transforms under pressure.

The researchers devised a more accurate technique for simulating Martian impact events in shock-recovery experiments. They employed a powerful "gun" to blast rocks with projectiles travelling over five times the speed of sound. This innovative approach surpassed previous methods that relied on transmitting shock waves through a steel chamber, which failed to accurately replicate the process that takes place during an actual impact event on Mars.

The transition of plagioclase into maskelynite was previously believed to occur at a shock pressure of 30 gigapascals (GPa), equivalent to 300,000 times the atmospheric pressure at sea level or 1,000 times the pressure experienced by submersible diving under 3 kilometres of ocean water. However, this recent study reveals that the transition actually takes place at approximately 20 GPa, which significantly differs from the findings of previous experiments.

"It has been a significant challenge to model an impact that can launch intact rocks from Mars while shocking them to 30 GPa. In this context, the difference between 30 GPa and 20 GPa is significant. The more accurately we can characterize the shock pressures experienced by a meteorite, the more likely it becomes that we can identify the impact crater on Mars from which it originated," said Paul Asimow, Eleanor and John R. McMillan Professor of Geology and Geochemistry.

The new study is described in a paper in the journal Science Advances.