Martian meteorites providing unprecedented insight into Red Planet

By Stephen Beech via SWNS

Meteorites that came from Mars 11 million years ago are providing unprecedented insight into the Red Planet's internal structure.

They were fired into space when a massive meteor plowed into the fourth planet from the sun, say scientists.

Now the volcanic rocks from Mars are revealing the exact nature of the Red Planet's mantle and crust.

Researchers say the rocks that formed around 1.3 billion years ago before being ejected into space also provide a glimpse into what the early Earth looked like.

Scientists at Scripps Institution of Oceanography, part of the University of California, San Diego, have conducted a detailed study of the Martian rocks collected from locations all over our own planet, including Africa and Antarctica.

Scripps Oceanography Professor James Day and his colleagues analyzed the chemical compositions of the samples from the Red Planet.

They say their findings, published in the journal Science Advances, are important for understanding not only how Mars formed and evolved, but also for providing precise data that can inform recent NASA missions such as Insight and Perseverance and the Mars Sample Return.

Study leader Day said: “Martian meteorites are the only physical materials we have available from Mars.

“They enable us to make precise and accurate measurements and then quantify processes that occurred within Mars and close to the Martian surface.

"They provide direct information on Mars’ composition that can ground truth mission science like the ongoing Perseverance rover operations taking place there.”

Day’s team used meteorite samples that all came from the same volcano, known as nakhlites and chassignites.

He explained that, around 11 million years ago, a large meteor impact on Mars sheared away parts of the planet and sent the rocks hurtling into space.

Some of them landed on Earth in the form of meteorites, with the first of them being discovered in 1815 in Chassigny, France, and then another in 1905 in Nakhla, Egypt.

More similar meteorites have been discovered since in locations including Mauritania and Antarctica.

Scientists are able to identify Mars as their place of origin because the meteorites are relatively young, so come from a recently active planet.

They also have "distinct" compositions of the abundant element oxygen compared to Earth, and retain the composition of Mars’ atmosphere measured on the surface by the Viking landers in the 1970s.

Day's team analyzed the two keystone nakhlite and chassignite meteorite types.

Nakhlites are "basaltic" - similar to lavas erupting in Iceland and Hawaii today, but are rich in a mineral called clinopyroxene.

Chassignites are almost exclusively made of the mineral olivine.

On Earth, basalts are a main component of the planet’s crust, especially under the oceans, while olivines are abundant in its mantle.

Day says the same is true on Mars.

The researchers showed that these rocks are related to each other through a process known as "fractional crystallization" within the volcano in which they were formed.

Using the composition of those rocks, the research team also showed that some of the then-molten nakhlites incorporated portions of crust close to the surface that also interacted with Mars’ atmosphere.

Day said: “By determining that nakhlites and chassignites are from the same volcanic system and that they interacted with a Martian crust that was altered by atmospheric interactions, we can identify a new rock type on Mars.

“With the existing collection of Martian meteorites, all of which are volcanic in origin, we are able to better understand the internal structure of Mars.”

He explained that they were able to do so because of the distinctive chemical characteristics of nakhlites and chassignites, as well as the characteristic compositions of other martian meteorites.

Day said these reveal an atmospherically altered upper crust to Mars, a complex deeper crust and a mantle where plumes from deep within Mars have penetrated to the base of the crust, while the interior of Mars’, formed early in its evolution have also melted to produce distinct types of volcanoes.

Day said: “What’s remarkable is that Mars’ volcanism has incredible similarities, but also differences, to Earth.

“On the one hand, nakhlites and chassignites formed in similar ways to recent volcanism in places like Oahu in Hawaii.

"There, newly formed volcanoes press down on the mantle generating tectonic forces that produce further volcanism.

“On the other hand, the reservoirs in Mars are extremely ancient, separating from one another shortly after the Red planet formed."

He added: "On Earth, plate tectonics has helped to remix reservoirs back together over time.

"In this sense, Mars provides an important link between what the early Earth may have looked like from how it looks today.”