Scientists: Earth’s Beginnings Can Be Found on Moon

UNM Team NASA Program Finalist

It is hard to think of the moon, floating serenely above the horizon on a warm summer evening, as a violent place.

Barbara Cohen is not fooled.

There was a time in our solar system’s deep past when the moon, the Earth and our other planetary neighbors were battered like overmatched, punch-drunk boxers. Massive chunks of asteroid pounded them again and again.

Then, around 3.9 billion years ago, the carnage quieted. Soon after, life on Earth got well and truly under way. That sequence is what makes the time so interesting — cataclysm as the foundation for life.

Most of the evidence on Earth for that cataclysm is long gone, victim of the mountain-building and erosion that perpetually reshapes our planet — which is why Cohen and a team of scientific colleagues have proposed to NASA a new journey to the moon.

Whatever caused that cataclysm hit everything in the neighborhood.

“When it comes crashing in, it hits the moon and hits the Earth,” explained Cohen.

Taking a trip to the moon these days is impractical. It has been nearly three decades since the last astronaut walked on the moon, and it is unclear when humans will return.

So a team of scientists is proposing to send robotic spacecraft to our nearest neighbor, to return with a few pounds of rocks.

Led by Michael Duke of the Colorado School of Mines, the team for the “Moonrise” mission includes Cohen and three of her colleagues from UNM’s Institute of Meteoritics.

NASA in July selected Moonrise as one of two finalists for the agency’s “New Frontiers” exploration program. The second finalist is a mission to Jupiter. The winner, to be announced next year, would launch by the end of the decade.

Founded in 1944 and based in UNM’s Department of Earth and Planetary Sciences, the Institute of Meteoritics has a long history of moon research.

Jim Papike, also part of the Moonrise team, was part of the original science team that studied the moon rocks brought back by NASA’s Apollo astronauts.

Even today, tiny samples of Apollo moon rock can be found at the UNM institute, undergoing yet more study.

New scientific tools, and new scientific questions, mean entirely new ways of studying the rocks the Apollo astronauts brought back to Earth in the late 1960s and early ’70s. It is as if the scientists are “studying lunar samples again for the first time,” as Papike put it.

But the samples are limited. The astronauts only went to a handful of places.

Much of the moon remains unstudied. It is as if a scientist was trying to understand Earth’s geology by grabbing a few samples of continental crust, missing the ocean basins entirely, said Chip Shearer, another of the UNM researchers on the Moonrise science team.

In the years since the Apollo missions, it has become clear that the missing piece of the lunar puzzle is a huge crater spanning the moon’s south pole — the South Pole-Aitken basin.

More than a thousand miles across, it is the largest known impact crater in the solar system.

It seems to be the remnant of that great 3.9 billion-year-old collision.

“The Earth,” the scientists wrote in their NASA mission proposal, “was born in violence.”

Collisions in the early solar system created Earth 4.5 billion years ago, as debris in the early solar system clumped together to form the planets.

Then a massive collision, likely with an object as big as Mars, smashed the Earth.

The impact flung off debris that clumped together anew to form the moon.

The bombardment continued, but the rain of solar system junk slowed to a drizzle after about 3.9 billion years ago.

The moon, the scientists wrote in their NASA proposal, “is a unique and pristine repository of the first 500 million years of Earth and inner Solar System history.”

Where Earth’s geologic processes have wiped out any obvious evidence of what happened back then, the moon’s relative serenity means the South Pole-Aitken basin’s rocks still bear clues about the impact.

The moon has always been seen by advocates of human space travel as the first step toward journeys to other planets.

But for scientists trying to understand Earth and those other planets, the moon also makes a useful steppingstone for other reasons.

First, it is close and therefore relatively easy to get to, noted Lars Borg, another of the UNM Moonrise team members.

Second, it is relatively pristine — no wind, rain or rising seas, no moving continents to obliterate the evidence of its history.

That makes it a perfect place to understand the solar system’s tumultuous past.

“All of us are convinced,” Papike said, “that the moon is a steppingstone to the solar system.”