Evrim Yazgin
Cosmos science journalist
An asteroid struck Mars 10.7 million years ago, sending pieces of rock hurtling into space. One of those chunks landed on Earth – scientists analysing it have made an interesting discovery.
The Martian rock landed somewhere in the US state of Indiana. It was rediscovered in a drawer at Purdue University in 1931 and named the Lafayette Meteorite. How the rock made it into the drawer remains a mystery. Now scientists have aged and studied how the rock formed.
Findings from the analysis of the Lafayette Meteorite are published in Geochemical Perspective Letters.
First, the researchers had to determine when the rock formed.
“We dated these minerals and found that they formed 742 million years ago,” says lead author Marissa Tremblay, who believes the minerals in the meteorite would have been produced through interaction with liquid water while still on Mars.
“Dating these minerals can therefore tell us when there was liquid water at or near the surface of Mars in the planet’s geologic past,” she says. “We do not think there was abundant liquid water on the surface of Mars at this time. Instead, we think the water came from the melting of nearby subsurface ice called permafrost, and that the permafrost melting was caused by magmatic activity that still occurs periodically on Mars to the present day.”
Tremblay’s team measured the amount of radioactive isotopes in the minerals to date the meteorite. Previous attempts to do so had likely been affected by other processes on Earth. This meant earlier research trying to determine the age of the meteorite was problematic.
The team’s focus on argon isotopes has proven to give the most accurate age.
“We have demonstrated a robust way to date alteration minerals in meteorites that can be applied to other meteorites and planetary bodies to understand when liquid water might have been present,” Tremblay says.
