An unexpected tool is giving us new insight into the fine structure of Mars’ outer layers.
Using meteorites that long ago broke away from the red planet about 11 million years ago and were hurled into space to eventually land on Earth, scientists have been able to study how volcanism shaped crust and mantle of Mars to ascertain the presence of silicate reservoirs that fueled their formation.
It’s very clever research, really – we have new information about the structure and evolution of Mars without having to go all the way to get it. Martian meteorites are proving to be quite an asset to understanding the planet’s history, and they’ll be delivered right here on our doorstep.
“Martian meteorites are the only physical material we have from Mars,” says geologist James Day of the Scripps Institution of Oceanography.
“They enable us to make precise and accurate measurements and then quantify the processes that have taken place inside Mars and near the surface of Mars. They provide direct information on the composition of Mars that can ground the mission’s science to the truth , like the ongoing operations of the Perseverance Rover taking place there.”
The meteorites examined by Day and his colleagues come in two forms; chassignites, after a rock found in 1815 at Chassigny, France, and nakhlites after a specimen discovered at Nakhla, Egypt, in 1905.
The two types of rock also have different compositions. Nakhlite is basaltic, contains inclusions of augite and olivine minerals. Chassignite is almost entirely olivine.
Here on Earth, basalts are more abundant in the crust, and olivine more abundant in the mantle. March is no different.
By conducting a careful examination and comparison of the two types of rocks and their unique chemical characteristics, the researchers were able to determine that they were formed in the same volcano about 1.3 billion years ago. Their difference is due to a process called partial crystallization, which occurs when different conditions cause liquid magma to solidify into different configurations.
The Nakhlites were part of the Martian crust; chassignites were part of the mantle below. Furthermore, some of the nakhlites were close enough to the crust to interact with and be altered by the Martian atmosphere.
“By determining that the nakhlites and chassignites are from the same volcanic system, and that they interacted with Martian crust that was altered by atmospheric interactions, we can identify a new type of rock on Mars,” says Day.
“With the existing collection of Martian meteorites, all of volcanic origin, we are able to better understand the internal structure of Mars.”
Interestingly, the two rocks show that volcanism on Mars is both similar and different from volcanism on Earth. Partial crystallization appears to occur in the same way, forming the basalt-dominant rock in the crust and the olivine-dominant rock in the mantle, just like volcanic activity here at home.
“On the other hand, the reservoirs on Mars are extremely ancient, separating from each other shortly after the formation of the red planet,” says Day. “On Earth, plate tectonics has helped mix reservoirs together over time. In this sense, Mars provides an important link between what the early Earth may have looked like to what it looks like today.”
The research was published in Advances in science.
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