When a meteorite hit Mars eleven million years ago, pieces of the Red Planet flew into space – and some of them landed on Earth in the form of meteorites, providing unprecedented evidence about the planet’s composition.
Now scientists at UC San Diego’s Scripps Institution of Oceanography have released a report following their detailed study of the Martian meteorites collected from locations around the world, including Africa and Antarctica.
Scripps geologist James Day and his colleagues analyzed the chemical composition of the Martian debris and said the results are important not only for understanding how Mars formed and evolved, but also for providing accurate data that will inform current NASA missions such as Insight and Perseverance and the Mars can inform. Example return.
“Mars meteorites are the only physical material we have available from Mars,” Day says. “They allow us to make precise measurements and then quantify processes that occurred on Mars and near 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.”
Day’s team pieced together its account of the formation of Mars using meteorite samples called nakhlites and chassignites, all of which came from the same Martian volcano and were named after the locations where they were found on Earth. The first of these was discovered in 1815 in Chassigny, France and then in 1905 in Nakhla, Egypt.
Since then, more such meteorites have been discovered in locations such as Mauritania and Antarctica. Scientists can identify Mars as their place of origin because these meteorites are relatively young and come from a recently active planet. They have different compositions that are more abundant in the element oxygen than compared to Earth, and maintain the composition of the Martian atmosphere as measured at the surface by the Viking landers in the 1970s.
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In the study published May 31 in the journal Science Advances, the team, funded by NASA, analyzed the two keystone meteorite types nakhlite and chassignite. Nakhlites are basaltic, similar to lava that erupts in Iceland and Hawaii today, but are rich in a mineral called clinopyroxene.
Chassignites are made almost exclusively from the mineral olivine. On Earth, basalt is a major component of the Earth’s crust, especially beneath the oceans, while olivines are abundant in the mantle.
The same goes for Mars. The team showed that these rocks are related through a process known as fractional crystallization in the volcano in which they formed. Using the composition of these rocks, they also show that some of the then-melted nakhlites contained parts of the crust near the surface that also interacted with Mars’ atmosphere.
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“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 said. “With the existing collection of meteorites on Mars, all of which are of volcanic origin, we can better understand the internal structure of Mars.”
The team, made up of colleagues from the University of Nevada Las Vegas and the French National Center for Scientific Research, was able to do this thanks to the distinctive chemical properties of nakhlites and chassignites, which reveal an atmospherically altered upper crust on Mars, a complex deeper crust and a mantle where plumes from deep within Mars have penetrated to the base of the crust. The interior of Mars, which formed early in its evolution, has also melted, creating several types of volcanoes.
“What’s remarkable is that Martian volcanism has incredible similarities, but also differences, with Earth,” Day says. “On the one hand, nakhlites and chassignites formed in similar ways to recent volcanism in places like Oahu, Hawaii. There, newly formed volcanoes press on the mantle and generate tectonic forces that cause further volcanism.”
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“On the other hand, the reservoirs on Mars are extremely old and separated from each other shortly after the formation of the Red Planet. On Earth, plate tectonics has helped reservoirs come back together over time. In that sense, Mars provides an important link between what early Earth may have looked like and what it looks like today.”
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