A meteorite found in Algeria has opened a rare window into nearly 2 billion years of Mars’ history that had largely been missing from the geological record.

Researchers at Boston College have determined that Northwest Africa (NWA) 13,441, a rock blasted from Mars before eventually reaching Earth, crystallized about 1.273 billion years ago. Its age places it squarely within a huge gap in the known record of shergottites, the most common type of Martian igneous meteorite. Even more unexpectedly, its chemistry points to a deep Martian source unlike any previously identified in this group.

“The characteristics of this meteorite were entirely surprising,” said Ethan Baxter, a Boston College professor of Earth and Environmental Sciences and founder of the university’s Center for Isotope Geochemistry. “No other Martian meteorite like this has an age of 1.27 billion years.”