CHEBARKUL, Russia —After a brilliant flash illuminated the sky on Friday morning like a second sun, Alyona V. Borchininova and several others in this run-down little town in the rust belt of western Siberian wandered outside, confused and curious.
They followed the light’s path to the town’s lakefront, where they trudged for about a mile over the open ice until they came to a startling sight: a perfectly round hole in the ice, about 20 feet in diameter, its rim glossy with fresh ice that had crusted on top of the snow.
“It was eerie,” Ms. Borchininova, a barmaid, said Saturday. “So we stood there. And then somebody joked, ‘Now the green men will crawl out and say hello.’ ”
Russians are still coming to terms with what NASA scientists say was a 7,000-ton chunk of space rock that came hurtling out of the sky at 40,000 miles an hour, exploding over the Ural Mountains, spraying debris for miles around and, amazingly, killing no one.
As the Russian government pursued the scientific mysteries of Friday’s exploding meteor by sending divers into the inky waters of the hole in Lake Chebarkul on Saturday, residents reacted with a kind of giddy relief and humor over their luck at having survived a cosmic near miss.
NASA estimates that when the meteor entered the atmosphere over Alaska, it weighed 7,000 to 10,000 tons and was at least 50 feet in diameter, a size that strikes the Earth about once every hundred years. They said it had exploded with the force of 500 kilotons of TNT.
The shock wave injured hundreds of people about 54 miles away in the industrial city of Chelyabinsk, most from broken glass; collapsed a wall in a zinc factory; set off car alarms; and sent dishes flying in thousands of apartments. Broken windows exposed people and pipes to the Siberian winter; many residents focused Saturday on boarding windows and draining pipes, to preserve heating systems.
If pieces of meteorite reached the surface, as NASA said was likely, they fell largely into the sea of birch and pine trees of Siberia, now blanketed in snow.
Lake Chebarkul is one of four sites the government believes to felt a significant impact, the minister of emergency situations, Vladimir Pushkov, told Interfax.
As the sun rose Saturday, the snow crystals sparkling in the sun like a million tiny mirrors, steam wafted from the site, apparently related to the work of divers, but the lake yielded little to shed light on the mystery.
Mr. Pushkov later said divers found nothing on the lake bed, but did not rule out meteor shrapnel as the cause of the hole.
“Experts are studying all possible places of impact,” he said. “We have no reports of confirmed discoveries.”
The discovery of a confirmed fragment could help scientists better apprehend the composition of the meteor, perhaps shedding light on how close it was to descending further before exploding from the heat, or of hitting the surface, potentially causing vastly more casualties in this region of military and industrial towns, a major nuclear research site and waste repository and other delicate infrastructure.
In Chelyabinsk, the worst hit town, most who had sought medical attention were released from hospitals by Saturday, the Ministry of Health reported. A total of 1,158 people, including 298 children, asked for medical assistance. Of these 52 people were hospitalized. By Saturday afternoon, 12 adults and three children remained in hospitals.
Health officials evacuated to Moscow a woman who broke two vertebrae after falling down a flight of stairs. One man’s finger was cut off by broken glass.
Overshadowing these misfortunes, a fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, was being hailed as a hero for saving 44 children from glass cuts by ordering them to crawl under their desks after she saw the flash. Having no idea what it was, she executed a cold war-era duck-and-cover drill, with salutary results.
Ms. Karbysheva, who remained standing, was seriously lacerated by glass that severed a tendon in her arm, Interfax reported; not one of her students suffered a cut.
