Meteorites Might Explain How Life on Earth Started

Meteor Shower
The Perseid meteor shower is pictured in the sky over Las Machotas in San Lorenzo of Escorial, Madrid, Spain. Reuters Pictures

Newsweek published this story under the headline "To Catch a Falling Star" on May 11, 1981. In light of the Perseid Meteor Shower of 2017, Newsweek is republishing the story.

On a clear night scores of meteors streak the sky as the Earth is showered with stardust memories of its own creation. These cosmological leftovers, known as meteorites*, range in size from many tons to microscopic grains. They contain material unchanged since the birth of the planets-and perhaps clues to the beginning of life. Says Martin Prinz, a geologist at New York's American Museum of Natural History: "Meteorites are the Rosetta stones of the origin of the solar system."

Last week the public got a look at the largest collection of meteorites in captivity when the museum opened its new Hall of Meteorites. Dominating the exhibit is the 34-ton Ahnighito, which crashed into Greenland thousands of years ago, Struggling to move it to the museum in 1897, explorer Robert Peary reportedly said, "I now understand the meaning of the word inertia." Ahnighito sits on six columns sunk into solid bedrock, surrounded by smaller iron meteorites like court attendants around their queen. Micrographs along the walls reveal "cosmic marbles" hidden in stony meteorites, and visitors are free to touch the fallen stars--some of them 4.5 billion years old.

Blue Ice: The hall testifies to a newfound zeal among scientists for "meteoritics." In search of pieces of our past, they are dredging the seabed for meteorites, harvesting them from the blue ice of Antarctica and collecting "microtneteorites" in the form of interstellar dust. Meteorites have been called the poor man's space probe, since space can come to Earth for a lot less than it costs to put a satellite--or a man--into orbit. Nevertheless, NASA's spending for meteorite studies has grown from $500,000 in 1973 to $3 million today.

The Chinese chronicled how "the stars fell like rain" in 687 B,C., but scientists didn't realize that meteorites come from space until 150 years ago. The French Academy of Sciences thought they were terrestrial rocks struck by lightning, and the belief that meteors were atmospheric quirks spawned the term meteorology. Large meteorites actually come from the asteroid belt, an area between Mars and Jupiter filled with scraps of material that failed to coalesce into planets. When asteroids collide, they throw off their debris in the form of meteoroids. Iron meteorites were once the metal cores of asteroids; some of the stony meteorites were their crust. Many smaller particles that flash through the sky may come from comets, since meteor showers occur with clock like regularity whenever the Earth crosses the tracks of certain comets. Although more than 100 tons of space material hit the atmosphere every day, most of it burns up or falls as dust. Only 150 or so meteorites fall on land annually, and only about-twenty are recovered. The world's collection numbers about 2,000--half of them at the Natural History Museum.

The occasional large meteorite that does make it to Earth arrives with a bang. Some 20,000 years ago, a meteorite left a 3/4-mile-wide crater in Arizona. No one has ever been hit directly by a falling star, but there is now suspicion that a gigantic meteorite may have wiped out the dinosaurs 65 million years ago. Rocks of that age contain high concentrations of the element iridium, which geologists say could only come from outer space. If a meteorite 3 miles in diameter had hit the Earth, the resulting dust cloud could have blotted out the sun for as long as five years, halting photosynthesis and wiping out much of the chain of life.

Stony meteorites often contain minerals so primitive that they tell scientists what the universe was like before the solar system formed 4.5 billion years ago. The 2-ton Allende meteorite that landed in northern Mexico in 1969 is studded with clumps of minerals distributed like raisins in a tea cake. "Some of these condensed from the nebula that created the sun and planets and haven't changed since then," says Lawrence Grossman of the University of Chicago.

Collapse: Allende is drastically changing ideas of how the nebula became the solar system. Astronomers have long believed that a swirling cloud of dust and gas collapsed into the solar-system, but they don't know what caused the collapse. Allende may provide an answer. It contains high amounts of a form of magnesium that comes from radioactive aluminum; the aluminum, in turn, is a product of exploding stars called supernovas. Because the aluminum decays quickly, any meteorite that contains its magnesium must have captured the aluminum soon after the supernova exploded, "A nuclear factory maybe 25 times bigger than our sun blew up just before the solar system was born," theorizes Gerald Wasserburg of the California Institute of Technology. The shock wave from such an explosion could well be the trigger that formed the nebula into sun, moons and planets.

Meteorites seem to be carrying another intriguing cosmic message. Scientists examining interstellar dust have discovered that it contains carbon-rich compounds similar to the primitive molecules believed to have given rise to life on Earth. That raises the possibility that the seeds of life arrived on this planet via meteorites--and that sprinkled stardust may have created life elsewhere in the universe.