Scientists are still trying to explain the September 2007 meteorite that careened through Earth's atmosphere and smashed into the ground in Peru while awestruck witnesses actually watched.
The witnesses' reports and the crater formed by the impact puzzled scientists. This meteorite seemed to have flown in much faster than scientists thought possible for an object of this kind, and it apparently survived entering Earth's atmosphere intact, rather than breaking apart as experts thought it should have.
"Many people thought this was a fake," said Peter Schultz, a Brown University planetary geologist who traveled to Peru to analyze the crater. "It just didn't make sense with what we understand of collisions with this type of fragile rock. Coming through the atmosphere they get stressed so highly that they typically break apart. But this one didn't do that."
Schultz went to investigate the crater along with Peruvian scientists and government officials a few months later. He found fractured lines in sand grains and compressed mixtures of earth and meteorite around the 49-foot-wide crater near the village of Carancas. These, along with widespread debris from the meteorite's crash landing, told him it landed at high speed, likely around 15,000 miles per hour at the moment of impact.
The meteorite was a common type, a chunk of silicate rock called a stony meteorite. Usually a projectile such as this would be slowed down by the drag of Earth's atmosphere. By the time it landed, it would be traveling at the normal terminal speed of any object falling from the sky, and would probably make a dent in the ground, not a crater.
"Essentially Carancas threw us this high-speed curveball," Schultz told SPACE.com. "The mystery is why it didn't slow down and how did it make it all the way to the Earth intact to form a crater? These are questions we have to resolve."
Scientists have several hypotheses about what might have happened. Perhaps as the meteorite hurtled through the atmosphere it melted and morphed, becoming more of an aerodynamic needle-shape that could resist stress and survive in one piece. Plus, this shape would help it hold on to its speed, since the surface area exposed to atmospheric drag forces would be reduced.
"But the mystery is, why wouldn't all objects reshape?" Schultz said. "Maybe it requires special circumstances, like the angle of entry."
Source: Xinhua/ Agencies
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