Water may have interacted with the Martian crust on broad scales as recently as 2.1 billion years ago, according to studies of a comparatively water-rich Martian meteorite with properties akin to rocks and soil studied by ’s Curiosity and Spirit rovers.
Northwest Africa 7034, a 320-gram crustal volcanic specimen obtained in Morocco two years ago, holds 10 times as much minerally bound water as the Shergottite, Nakhlite, and Chassignite (SNC) classifications that dominate the relatively small population of Martian meteorites recovered on Earth.
Carl Agee, director of the University of New Mexico’s Institute of Meteoritics, led an examination of the meteoritic outlier by a team of 16 experts. Their findings appear in the Jan. 3 edition of Science Express.
NWA 7034 also emerges richer in geochemical features than its SNC siblings but on a par with geochemical characterizations emerging from Curiosity’s observations at Gale Crater and the Spirit Mars Exploration Rover at Gusev Crater. They also match the broad-scale geochemical signatures of the Martian terrain from observations made with the gamma ray spectrometer aboard’s Mars Odyssey, according to the findings.
“The meteorite has 10 times more water locked up in the minerals than any previous Martian meteorite. That in itself is an exciting discovery. What that means exactly for Mars and its surface environment is still an open question,” Agee told Aviation Week. “But it raises the possibility that surface activities involving water extended well into Martian geological times, not simply back to the earliest era. There may have been places on Mars at least 2 billion years ago where there was enough water present to interact with these volcanic rocks and incorporate into the mineral structure.”
Scientists generally separate Martian history into three broad eras synched to the formation of the Solar System 4.6 billion years ago, though the planet’s transition from an early warmer and wetter environment to the current cold, dry realm is not straightforward.
The Noachian era extended over Mars’ first 1 billion years and appears to have featured flowing water and precipitation. The Hesperian, which followed over the next 500 million to 1.5 billion years and predated the Amazonian, was marked by falling temperatures and changes to the atmosphere. Near surface water froze and pooled underground.
NWA 7034, with its emerging links to the Curiosity, Spirit and Odyssey observations, is raising further questions about the already unclear Martian origins of the SNCs, according to Agee and Andrew Steele, a co-investigator from the Carnegie Institution’s Geophysical Laboratory.
The analysis of NWA 7034’s macro molecular organic carbon, led by Steele, established the meteorite’s connection to the Martian surface.
Agee describes NWA 7034 as a “different kind of volcanic rock” — a breccia, or conglomerate of fragments from rocks that were shattered by volcanic violence and then welded back together by the extreme heat. Those textural characteristics of NWA 7034 further distinguish it from the SNCs, as well as a fourth category of Martian meteorite available to scientists and represented by Alan Hills 84001. A much older meteorite recovered from Antarctica, AH84001 became the focus of contested claims in 1996 that it hosted fossilized evidence of Martian microbial life.
“There are a couple of ways to look at this high water content,” Agee says of NWA 7034.
In one scenario, a volcano emerges from the Martian terrain, heating the rock structure and melting the permafrost, allowing the two to interact before an asteroid or comet struck with enough energy to launch NWA 7034 on a trajectory that would intersect the Earth’s orbit.
In an alternate scenario, the Martian climate did not change so severely, permitting an interaction between the breccia and surface or ground water.