CAPE CANAVERAL, Florida About 5 million years ago, an asteroid or comet slammed into Mars so hard that rocks and other debris launched into space.
After traveling millions of years, some eventually landed on Earth, becoming the biggest of three main types of meteorites hailing from the Red Planet.
Now researchers say they have pinpointed the source of those Martian meteorites classified as the "shergottites." The finding, if confirmed, would give scientists fresh insights into Mars' history and evolution.
"If one were able to say, 'Oh, this Martian meteorite is from exactly this spot on Mars,' then that would have significant added value to what you could get out of it," said Carl Agee, meteorite curator and director of University of New Mexico's Institute of Meteoritics.
"We'd know exactly what material it is made of, we'd know how old it was when it formed. You'd get more of the missing pieces of the puzzle of how Mars formed," Agee said.
University of Oslo planetary scientist Stephanie Werner and colleagues say they have done just that.
The shergottites, Werner said, come from a 34-mile (55-km) wide impact basin known as Mojave Crater in the planet's equatorial region.
The scientists point to the crater's large size, relative youth and chemical composition as good matches for the shergottites, which account for about 75 percent of the roughly 150 Mars meteorites found so far.
Others say the evidence is far from ironclad.
"The (study) strikes me as somewhat speculative," said Agee, who was not involved in the research.
Werner, for example, says the shergottites crystallized some 4.3 billion years ago, roughly the same age as the crater's original terrain.
But Agee said most scientists believe the shergottites are much younger.
"I'm not convinced," Agee said.
Werner's research is published in this week's issue of the journal Science.