Black Beauty, a rock discovered in the Sahara Desert, has been identified as the oldest Martian meteorite ever found, scientists say.
Earlier research had suggested Black Beauty was about 2 billion-year old, but new tests indicate the rock actually dates to 4.4 billion years ago.
The dark and glossy meteorite would have formed when the Red Planet was in its infancy.
The research is published in the journal Nature.
Lead author Prof. Munir Humayan, from Florida State University, US, said: “This [rock] tells us about one of the most important epochs in the history of Mars.”
There are about 100 Martian meteorites, but almost all of them are younger, dating to between 150 million and 600 million years old.
They would have fallen to the Earth after asteroid or comet impacts had dislodged them, setting the rocks free to travel through space before eventually crash landing here.
This particular Martian meteorite, which is formed of five fragments, is much older.
Black Beauty rock has been identified as the oldest Martian meteorite ever found
An earlier analysis of one piece, called NWA 7034, put the age at 2 billion years.
But this latest research has found that another piece, NWA 7533, dates to 4.4 billion years ago, which suggests that NWA 7034 also must be older.
The team said it would have formed when Mars was just 100 million years old.
“It is almost certainly coming from the southern highlands – the cratered terrain that makes up the southern hemisphere of Mars,” said Prof. Munir Humayan.
This would have been a turbulent period of Martian history, when volcanoes were erupting all over the surface.
Prof. Munir Humayan explained: “The crust of Mars must have differentiated really quickly, rather than gradually over time. There was a big volcanic episode all over the surface, which then crusted up, and after that the volcanism dropped dramatically.
“When it did this it also must have out-gassed water, carbon dioxide, nitrogen and other gases to produce a primordial atmosphere… and also a primordial ocean.”
He added: “This is a very exciting period of time – if there were to be life on Mars, it would have originated at this particular time.”
Prof. Munir Humayan said that team now plans to study the rock to see if there were any signs of past life. But he added that while the rock was lying in the Sahara Desert, living organisms probably would have occupied it, masking potential evidence.
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Scientists have discovered that a dark lump of rock found in the Moroccan desert in 2011 is a new type of Martian meteorite.
Weighing 320 g, the stone has been given the formal name Northwest Africa (NWA) 7034 – but is nicknamed “Black Beauty”.
Its texture and chemistry set it apart from all previous objects picked up off the surface of Earth but known to originate on the Red Planet.
The researchers’ analysis, reported in Science magazine, shows the meteorite to be just over two billion years old.
The study was led by Carl Agee from the University of New Mexico, US.
“It has some resemblance to the other Martian meteorites but it’s also distinctly different in other respects, both in the way it just looks in hand sample, but also in its elemental composition,” Carl Agee said.
There are just over 100 Martian meteorites currently in collections worldwide. They were all blasted off the Red Planet by some asteroid or cometary impact, and then spent millions of years travelling through space before falling to Earth.
Scientists say that a dark lump of rock, nicknamed Black Beauty, found in the Moroccan desert in 2011, is a new type of Martian meteorite
Their discovery was mostly chance (few were seen in the act of falling) but their dark forms mean they will have caught the eye of meteorite hunters who scour desert sands and polar ice fields for rare rocks that can trade for tens of thousands of dollars.
Virtually all the Martian meteorites can be put in one of three classifications referred to as Shergotty, Nakhla, and Chassigny after key specimens. Scientists will often refer to these rocks simply as the SNC meteorites.
Prof. Carl Agee and colleagues argue that NWA 7034 now be put in its own class.
This rock is a basaltic breccia in character. It is made of a jumble of fragments that have been cemented back together in the high temperatures of a volcanic eruption. There are many examples of Moon meteorites that look this way, but no SNC ones.
Geochemically, NWA 7034 is dominated by alkali elements such as potassium and sodium. This is precisely what the robot rovers studying basalts down on the ground on Mars also see. This is not a trait seen in the SNC meteorites, interestingly.
Prof. Carl Agee’s team also see much more water in the new meteorite – about 6,000 parts per million. That is about 10 times more water bound into the rock than is the case in the most water-rich SNC specimens.
This says something about the environment in which the rock formed, indicating there was a much greater abundance of water to interact with the basalt.
“This rock is from two billion years ago and a lot of the SNCs are from only about 200-400 million years ago,” explained Prof. Carl Agee.
“And of course those most recent times on Mars have witnessed a cold, dry planet with a thin atmosphere. A lot of people believe that early Mars, on the other hand, was a lot warmer and a lot wetter, and maybe even a harbor for life.
“So, what happened in between? When did this transformation to drier conditions occur? Well, NWA 7034, because of its greater age, may be able to address those questions.”
A meteorite from Mars has been given to science to help unravel the Red Planet’s secrets.
The Natural History Museum (NHM) in London has acquired the 1kg piece of the Tissint rock thanks to an anonymous benefactor.
The meteorite was seen to land in Morocco last July and retrieved quickly, resulting in minimal contamination with Earth.
Researchers hope Tissint’s geochemistry will provide insights into past conditions on Mars and the possibility that it may once have hosted life.
Just 61 out of the 41,000 meteorites known to science come from Mars. To get here, they would have been blasted off the surface of the Red Planet by a mighty impact and then travelled through the Solar System before crashing to Earth.
There have only been four other witnessed Martian meteorite falls, the last one in Nigeria in 1962.
“Tissint fell in a dry area, and was picked up soon after it fell and has absolutely minimal contamination,” explained Dr. Caroline Smith, meteorite curator at the NHM.
“It is as if it has just been blasted off Mars. It is effectively a pristine sample of Mars.”
The Natural History Museum (NHM) in London has acquired the 1kg piece of the Tissint rock thanks to an anonymous benefactor
NHM staff will use computed tomography (CT) scans to look at the internal structure of the rock, and perform tests to determine its chemistry.
Researchers will look for minerals formed in the presence of water, and for any signs of organics – carbon-rich molecules.
Energy, water, a source of carbon are the prerequisites for life as we know it. Finding evidence for any of these phenomena in Tissint tells scientists something about how habitable Mars might have been in the past.
This meteorite also contains a lot of glassy material called maskelynite, formed through the force of impact, most probably the blast that ripped it from the surface of Mars.
Scientists will analyze the gas trapped in bubbles in the glass to discern more about the Martian atmosphere.
Indeed, this is how meteorites like Tissint can be tied to the Red Planet – the gases held in the rocks contain types and abundances of atoms that are very similar to the atmosphere sampled by robots on Mars today.
Collectively, the class is known as the SNC group of meteorites, named after three representative members: Shergotty, Nakhla, and Chassigny.
“Looking at similar Mars samples, the ejection date of this sample could range from about 600,000 years ago up to about 17 million years ago,” said Dr. Caroline Smith.
Science would dearly love to retrieve fresh samples of Martian rock for study in Earth labs. The scale and breadth of the analytical techniques that are available in the best-equipped facilities dwarf those which can be deployed on a rover, even a huge (900kg) vehicle like the Curiosity robot just dispatched to the Red Planet by NASA.
But a Mars sample return mission is technically very challenging and would probably cost billions of pounds.
The NHM acquisition has been made possible through the generous support of a private donor.
The donor commented: “My family and I are delighted to partner with the Museum in such an important acquisition. We all now set off on an exciting voyage of discovery. Man may not set foot on Mars in the near future, but Mars has come to us.
“This close-up view will bring new scientific understanding, to spur our children on to further exploration on the surface of the planet itself.”
The rock first came into the possession of Darryl Pitt of the Macovich Collection in New York City. He had heard rumors of its existence over a period of weeks following the observed fall to Earth and had set out to track down its whereabouts. With every lead turning into a dead end, he nearly gave up until he received a helpful phone call.
Darryl Pitt offered it to the NHM with the anonymous benefactor funding the purchase.
“It is both humbling and an honor to be part of this meteorite’s journey, and the Natural History Museum is the perfect final residence,” Darryl Pitt said.