Uncovering a Novel Martian Rock Type Without the Actual Rock: A Scientific Breakthrough

a Martian space rock

A group of researchers conducted a chemical examination of chassignites and nakhlites, like the one shown, two types of Martian meteorites discovered on Earth, with only 35 examples in existence. Photo: Scripps Institution of Oceanography at UC San Diego

The collection of meteorites from Mars is remarkably limited: Under 400 of the recognized celestial stones found here come from the Red Planet. 

Even scarcer are the nakhlites and chassignites, two of the three primary categories of Martian meteorites, with just 35 specimens globally, as per The Meteoritical Society. However, despite possessing many of these rocks for years, scientists have had limited knowledge about them. James Day, a geologist and geochemist at UC San Diego, aimed to unveil their mysteries. 

Following the initial comprehensive analysis of this assortment by him and a team of researchers, they stumbled upon an unexpected discovery — a novel type of Martian rock — although no actual rock or any similar matches have been found on Earth.

The revelation is rooted in a mysterious geochemical signature ingrained within some of the samples. This distinctive rock type likely represents Mars’ crust, as indicated in the study published in the journal Science Advances. 

“It’s an unmistakable identifier. There’s no other possibility. It’s glaringly evident in the data,” he expressed. “We will likely encounter these rocks on Mars.”

Illustration of the Nahkla meteorite

A Martian meteorite fell in Nakhla, Egypt, in 1905. Similar specimens have been classified as nakhlites.Photo: Universal History Archive / Contributor / Universal Images Group via Getty Images

NASA approximates that around 48.5 tons of ancient meteoric material descend upon Earth daily, yet a significant portion vaporizes in the atmosphere or plunges into water, which covers over 70 percent of the globe. Over 82,000 meteorites have been unearthed, but merely about 0.5 percent originated from Mars. 

All known Martian meteorites originated from volcanoes. The nakhlites and chassignites seem to be interconnected through a process known as “fractional crystallization,” a primary mechanism for inducing chemical alterations in magmas. Scientists speculate that these two types emerged from the same volcanic system, ejected into space subsequent to a substantial meteor impact on Mars approximately 11 million years ago. This collision potentially propelled debris out of the Martian atmosphere into space. Over time, some of these fragments might have made their way to Earth.

Upon meticulous examination, the team discerned traces of the Martian atmosphere in certain nakhlites — though not in all of them. The composition aligned with the readings obtained by NASA’s Viking landers in the 1970s. The researchers theorize that the molten nakhlites flowed over the Martian surface, or just beneath it, melting portions of the crust and assimilating them. 

Artistic representation of the Viking spacecraft's landing sequence

NASA’s Viking landers gathered atmospheric data on Mars in the 1970s. Photo: NASA / Kennedy Space Center illustration

“Imagine being a Martian and having a fragment of Earth in your meteorite collection, originating from Hawaii. Unaware of its Hawaiian origin, you possess this rock,” Day illustrated. “When this rock forms, it melts, flowing over highly altered rocks, which retain traces of Earth’s atmosphere.”

By utilizing sulfur isotopes, altered in Mars’ atmosphere, the team could extrapolate the appearance of these rocks. The rocks, yet to be named by the team, exhibit basaltic characteristics. Basalts are abundant on Earth, forming the bedrock of the ocean floor and in regions where lava has flowed, such as Hawaii and Iceland.  

These rocks are notably ancient, given that the nakhlites themselves date back roughly 1.3 billion years. For crustal rocks to be integrated into the nakhlite material, they must be even older, Day explained. 

NASA observing a Martian volcano from orbit

However, why hasn’t any Martian crust material reached Earth in the form of a meteorite? Day posits that these rocks likely do not retain their structure well, making it improbable for fragments to survive a catastrophic meteor impact on Mars. Even if some debris were ejected into space, the chances of it reaching Earth’s surface intact are exceedingly slim.  

“It’s an unmistakable identifier. There’s no other possibility.”

In addition to the speculated new rock type, the study sheds light on the internal composition of the Red Planet — exhibiting similarities to Earth in some aspects and stark differences in others. The team proposes that Mars possesses an altered upper crust, a complex deeper crust, and a mantle penetrated by plumes at the base of the crust. During the planet’s early evolution, its interior liquefied, giving rise to distinct types of volcanoes, a configuration that seems to have endured. 

Nakhlites and chassignites formed akin to volcanic rocks in Hawaii and Iceland. In these regions, volcanic activity is spurred by the pressure exerted by volcanoes on the mantle, generating tectonic forces that promote further volcanic eruptions. However, on Earth, plate tectonics have homogenized the reservoirs supplying the volcanoes over time, unlike Mars, where the reservoirs have remained distinct.

Researchers examining a Chassigny meteorite

NASA’s Perseverance rover, a laboratory on wheels, has been gathering samples from the Jezero crater on Mars since 2021 for subsequent scientific analysis. This region, an ancient desiccated delta, is believed to have harbored microscopic life forms in the distant past. However, the Mars Sample Return mission, aimed at transporting rocks and grains to Earth for examination, faces challenges. Escalating costs have led to layoffs and warnings of potential cancellation from Congress. The agency is now appealing for external assistance to salvage the mission.

Day remains hopeful that NASA will devise a means to bring these samples back. Nevertheless, even if this endeavor fails, there is still a wealth of knowledge that can be gleaned from these meteorites. 

“One might assume that we have exhausted all avenues with these rocks. That’s not the case,” he remarked. “There is still a plethora of scientific exploration awaiting.”

Evan Brooks

Evan is a seasoned reporter with an insatiable curiosity for the latest gadgets and breakthroughs in science and tech.

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