Martian meteors origins have been explained after scientists compared the crystalline structure of shergotite meteorites that landed on Earth and composition of the Mojave Crater on Mars. Due to the similarities it is believed that 75% of more than 150 Martian meteorites on Earth resulted from a single impact on the Red Planet that ejected all of the mass into space and flung it millions of miles to land on Earth. These Martian meteors are placed in three categories: shergotites, nakhlites, and chassignites. The age of nahklites and chasssignites has been set at 1.3 billion years, but the age of shergotites is proving more difficult to pin down.
Stephanie Werner, a planetary scientist at the University of Oslo led the study to determine the origin of the Martian meteor. They went on to try to determine the age of the Mojave Crater, which is 34 miles wide and lies near the Mars equator, to further attribute the meteors to this area. The main specimen was Yamato 000593, a 30 pound rock that is believed to be at least 150 million years old due to its internal crystalline structure. The team estimated the age of the Mojave Crater by using a technique known as crater counting, where the size and number of craters in an area are counted to give an idea of when the impacts occurred. Generally, areas that feature many large concentrated impacts are older, where smaller sparser blemishes are younger. Crater counting led Ms. Werner and her team to estimate the Mojave Crater was formed 4.3 billion years ago.
Here there is an issue, despite the Martian meteor origins explained the apparently huge difference in age between the crater and Yamato 000593 raised eyebrows for the whole team. Ms. Werner had an explanation however, saying that she theorizes the crystals in the meteorite were altered when they melted during the descent through the atmosphere. Because heat and pressure are such overpowering factors in the formation of stones and crystals on Earth, it makes sense they would have the ability to alter the composition of the Martian meteors as well. Ms. Werner has said she is excited to see how this difference is discussed in the future.
Although it so far is the best answer available, several of Ms. Werners colleagues are sceptical that it is completely accurate explanation for the Martian meteors. Inconsistencies in age aside, it has been pointed out that one sample used in the comparison of crystalline structures between the meteorites and the Mojave Crater has had much more exposure to cosmic rays than the rest, making its relevance and reliability as a comparative test subject questionable.
Although all the answers may not be at hand just yet regarding the Martian meteor, research into the composition of Mars is considered an important field of study. It is expected that a better understanding of the ancient time line of Mars will allow researchers to make informed decisions about how it was formed, when it cooled, and what caused the mysterious loss of its magnetic field. Having the Martian meteor origins explained is a big step to answering questions about the Red Planet and the universal system that Earth is also a part of.
By Daniel O’Brien