About 5 million years ago, an asteroid or comet slammed into Mars so hard that rocks and other debris launched into space.
Some eventually landed on Earth, becoming the "shergottites," the biggest of three main types of meteorites from Mars.
Now researchers say they have pinpointed the source of the shergottites. The finding, if confirmed, would give scientists fresh insights into Mars' history.
"If one were able to say, 'Oh, this Martian meteorite is from exactly this spot on Mars,' then . . . we'd know exactly what material it is made of, we'd know how old it was when it formed," said Carl Agee, the director of the University of New Mexico's Institute of Meteoritics.
University of Oslo planetary scientist Stephanie Werner and colleagues say the shergottites come from the 55-km-wide (34-mile-wide) Mojave Crater in the planet's equatorial region. They point to the crater's large size, relative youth and chemical composition as good matches for the shergottites.
Others say the evidence is far from ironclad. Agee said most scientists believe the shergottites are much younger.