Agee found strong experimental support for a theory that the infant Earth completely melted to a depth of hundreds of miles, allowing heavy metals to separate rapidly from lighter rocky materials — like oil fleeing from water.
“That’s how you can go from a lab experiment a cubic millimeter in size to saying sweeping things like, ‘The whole process of differentiation and core formation wrapped up very fast in geologic terms, taking only a few million years,’ ” he says with a lingering flutter of amazement in his voice. “It’s incredible when you think about it.”
A Bit of Mars in the Lab
Despite these impressive successes, Agee’s interests began to drift to meteorites — another youthful passion — when he was named the director of the Institute of Meteoritics in 2002. The agency was founded in 1944 as a meteorite collection, but by the time Agee took over, it had evolved into a research collection dedicated to studying space from the ground.
That work brought Agee in contact with all sorts of exotic objects, including meteorites that apparently originated from the moon and Mars. But nothing prepared him for Black Beauty or, as it was originally cataloged, NWA 7034.
Like so many meteorites that came to Agee’s attention, this one racked up a lot of miles first. It was found by a nomadic meteorite hunter in Morocco (hence “NWA,” for Northwest Africa) who sold it to a local dealer, who sold it to a major collector named Jay Piatek, who finally donated it to the institute.
Agee treated NWA 7034 like any other new arrival, prodding it with his high-tech tools to classify it. “It’s sort of like a treasure hunt,” he says. “Usually after a session on the electron microprobe, I can say exactly what kind of meteorite it is. Is it a Martian? Is it a lunar? Maybe it is a terrestrial rock that just looks like it might have been a lunar or a Martian. We call those meteorwrongs.”
NWA 7034 didn’t fit into any category, however. Agee grew so frustrated that he set it aside for a month, then tried again. This time he cut into it with a diamond saw and began analyzing it from the inside. He was still puzzled by the result. “It was suggestive of Mars, but it wasn’t like any other Martian meteorite,” he says. Strangest of all, it was full of water — 10 times as much as any other known piece of the Red Planet. That oddity ultimately proved to be the key clue.
Black Beauty did not match up with the other Mars meteorites, Agee realized, but it did closely resemble something else: the rock and soil samples analyzed by NASA’s Spirit rover at Gusev Crater on Mars, where the minerals show clear evidence that water was once present.
By dumb bad luck, all the other Mars meteorites had originated from the dry parts of the planet. In contrast, NASA deliberately sent its rovers to places that looked like they were once wet. With Black Beauty, scientists on Earth finally had a sample that matched the potentially life-friendly locations that the rovers were exploring.
At last, the pieces of Black Beauty’s story began to fall into place. Radioactive dating indicated that the meteorite is 2.1 billion years old, placing its origin in the middle of a little-understood stage of Martian geologic history known as the Amazonian.
“It’s a period when Mars was probably transforming from a wet, warm place — perhaps a harbor for life — to what we see now: a dry, cold, inhospitable environment, not good for life,” Agee says. He interprets Black Beauty as a volcanic rock that got exposed to a lot of water on the way up to the Martian surface. Perhaps it erupted through groundwater, or perhaps it was part of a geothermal system.
“We don’t know what the state of the water was. We just know that there was plenty of it, and that’s very exciting,” Agee says.
The rock sat on the surface for eons until an asteroid struck Mars and flung bits of its crust into space. One chunk of that debris floated around in space for roughly
5 million years — Agee can tell by the traces of cosmic radiation etched into the rock — until it fell to Earth, and ultimately into Agee’s lab.
To Horton Newsom, a co-investigator on the Curiosity rover and Agee’s colleague at the University of New Mexico, having access to a water-rich Mars rock here on Earth is a revelation. “This sample is big enough to study with a wide range of laboratory techniques that really expand our knowledge of the surface of Mars,” he says.
Black Beauty will allow NASA scientists to recalibrate chemical results from their rovers and from orbiters. It will deepen our understanding of Mars’ formation as well as its comparatively recent climate history — “the whole planet, across space and time.” And, Newsom adds, “it is just thrilling to think that these samples you can hold are from other worlds.”
Agee has plenty of research yet to do on Black Beauty, including partnering with other scientists to search for traces of organic material that would help answer whether Mars could truly have supported life. But he is already anticipating what other inaccessible places he can get his hands on. “The next challenge is to find a meteorite from Venus,” he says. “That would be a jackpot for sure!”