An unexpected tool gives us new insight into the fine structure of Mars’ outer layers.
Using meteorites that broke off from the red planet way back about 11 million years ago and were flung into space to eventually land on Earth, scientists have been able to study the way volcanism shaped Mars’ crust and mantle to reveal the presence from silicate reservoirs. nourished their formation.
It’s actually quite a clever bit of research: we have new information about the structure and evolution of Mars, without having to go all the way. Meteorites from Mars are proving to be a great resource for understanding the planet’s history, and they’re delivered right here to our homes.
“Mars meteorites are the only physical material we have available from Mars,” says geologist James Day of the Scripps Oceanography Institute.
“They allow us to make precise and accurate measurements and then quantify processes that have occurred on Mars and close to the surface of Mars. They provide direct information about the composition of Mars that can inform truth mission science such as the ongoing Perseverance rover operations taking place there.”
The meteorites examined by Day and his colleagues come in two forms; chassignites, from a rock found in 1815 in Chassigny, France, and nakhlites from a specimen discovered in 1905 in Nakhla, Egypt.
The two types of rock also have different compositions. Nakhlite is basalt and contains inclusions of the minerals augite and olivine. Chassignite is almost entirely olivine.
Here on Earth, basalt is more abundant in the crust, and olivine more abundant in the mantle. Mars is no different.
By conducting a careful examination and comparison of the two types of rocks and their unique chemical properties, 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 fractional crystallization, where different conditions cause the liquid magma to harden into different configurations.
The nakhlites were part of the crust of Mars; the chassignites were part of the mantle below. Furthermore, some nakhlites were close enough to the crust to interact with and be changed by Mars’ atmosphere.
“By establishing that nakhlites and chassignites come from the same volcanic system, and that they interacted with the Martian crust that was altered by atmospheric interactions, we can identify a new rock type on Mars,” Day says.
“With the existing collection of Martian meteorites, all of which are of volcanic origin, we can better understand Mars’ internal structure.”
Interestingly, the two rocks show that volcanism on Mars is both similar to and different from volcanism on Earth. The fractional crystallization appears to occur in the same way, creating basalt-dominant rocks in the crust and olivine-dominant rocks in the mantle, much like the volcanic activity here at home.
“On the other hand, the reservoirs on Mars are extremely old and separated from each other shortly after the formation of the red planet,” says Day. “On Earth, plate tectonics has helped reservoirs come back together over time. In this sense, Mars provides an important link between what early Earth may have looked like and what it looks like today.”
The research was published in Scientific progress.