Mars meteorites may be older than previously thought

New Scientist : The age of shergottites, which make up 80% of all meteorites that have fallen to Earth from Mars, has been a matter of debate: Radioactive lead in the samples indicates an age of 4.1 billion to 4.3 billion years, whereas other isotopes indicate an age of just 150 million to 600 million years. Now a team of researchers led by Stephanie Werner of the University of Oslo in Norway say that based on the meteorites’ composition, all shergottites probably originate from Mars’s Mojave crater and thus are most likely about 4.3 billion years old. They say that the discrepancy in isotope dating may be due to the very high pressures exerted on the meteorites while the crater was being formed, pressures that could have altered their various minerals and reset their ages.