Mars meteorite reveals its age
Long difficult to estimate, date of space rocks' formation emerges with new technique
Providing a tool for unlocking secrets of the early solar system, a new technique accurately determines the age of meteorites, scientists report in the July 25 Nature.
Scientists disagree over estimates of meteorites’ ages because it’s hard to distinguish between when the rocks formed and when they got seared from an impact and flung into space toward Earth.
UCLA geochronologist Axel Schmitt and colleagues began by examining the structure of a meteorite’s mineral crystals, which differs depending on whether the crystals solidified gradually within a lava flow or rapidly after the intense heat and pressure of an impact. Then they determined the age of the crystals by measuring the ratio of uranium to lead. Uranium has two isotopes, each of which decays into its own lead isotope, providing researchers with multiple radioactive-dating measurements to cross-check for consistency.
The team analyzed the Martian meteorite Northwest Africa 5298 and found large, interlocking crystals about 187 million years old, which suggests that the rock formed during a volcanic eruption back then. The researchers also found zircon crystals that likely formed from an impact no more than 22 million years ago.
Schmitt says that by applying the technique to rocks from Mars, the moon, asteroids and even Earth, scientists can learn about when volcanoes erupted in the distant past.