Scientists have discovered the origin of roughly three-quarters of all Martian meteorites found on Earth. The Martian rocks are most likely from a single giant crater on Mars.
Around 75 percent of all Martian meteorites on Earth are referred to as Shergottites. These meteorites are named after a single meteor that crashed at an Indian town named Shergati. A team of researchers was able to determine that these Shergottites came from a 34-mile Martian crater called "the Mojave Crater" found in the Oxia Palus quadrangle on Mars.
By comparing the Martian meteorites and the material that makes up the Mojave Crater, scientists were able to determine that many of the igneous rocks that make up Martian meteorites originated from this specific area of the Red Planet.
"We tried to find good arguments to convince ourselves that [Mojave Crater] was five million years or younger," said Stephanie Werner, a planetary scientist at the University of Oslo and the lead author of the study. "You don't expect this size of crater so recently formed, statistically at least."
The team was also able to determine the age of the crater using a technique called "crater counting." By counting the number of craters located in a single area, the researchers were able to come up with a rough estimate regarding when these Martian rocks were ejected from the planet. In general, a higher number of larger craters in a single location means that the location is more ancient compared to areas with smaller craters. The team was able to estimate that the Mojave Crater was around 5 million years old.
"We show that the less than 5 million-year-old and 55-km-wide Mojave Crater is the ejection source for the meteorites classified as shergottites. Shergottites and this crater are linked by their coinciding meteorite ejection ages and the crater formation age, and mineralogical constraints," said Werner and her colleagues.
Aside from crater counting, the researchers also used data gathered by the Mars Express Orbiter and the Mars Reconnaissance Orbiter to complete their analysis. According to the data, the Shergottite meteorites and the Mojave Crater both had similar amounts of pyroxene minerals.
When analyzing the age of the Shergottite meteorites however, the scientists found a major discrepancy. The plateau surrounding the Mojave crater is believed to be around 4.3 billion years old. On the other hand, the Shergottite meteorites have been found to be around 150 to 600 million years old based on the crystallization of the meteorites. Werner believes that the discrepancy in age is due to a resetting of the crystallization age of the meteorites due to melting, which can be caused by meteorite impacts.
"It will be quite interesting to see how that will be discussed in the future," Werner said.
The researchers published their findings in the online journal Science.