How Big Was That Russian Meteor?

( By Corey S. Powell | February 15, 2013 4:01 pm )

Task1 Could you fill in the blanks in the text with the sentences below?

A. Bits of it hit the ground, but they did not cause significant destruction, based on early reports.

B But Deep Space Industries, one of the private companies angling to build a fleet that could monitor asteroids and ultimately mine them for resources, is eager to change that.

C. A news report in the journal Nature now estimates that it probably weighed 7,000 metric tons when it entered the atmosphere, which would make it the biggest object to hit Earth since the Tunguska event in 1908.

D. Early reports pegged it as being much smaller, probably because the vast majority of the meteor disintegrated in the atmosphere.

E. Early news stories stated that similar bolides occur a few times a year.

F. The fragments hurtled through the atmosphere, trailing smoke across the sky and causing a strong shock wave that shattered windows in the city of Chelyabinsk, causing many injuries.

G. Meteor strikes of this size are not really that unusual. Several occur every year, according to the Russian Academy’s statement about today’s event.

As more information has been gathered about the meteor, numbers are being revised. Earlier in the day, the Russian Academy of Sciences stated that the meteor probably weighed 10 tons. _____1___I've left the story below as I wrote it earlier in the day, because it seems evident that all the facts are not yet in, and numbers like this may still change.

The meteor that streaked across Russia today probably weighed 10 tons as it entered the atmosphere at a velocity between 33,000 and 45,000 miles per hour, according to the Russian Academy of Sciences. And it probably broke up at 20 to 30 miles above the surface.___2____ According to the Russian academy, a meteor of this size will typically release most of its energy at an altitude between 9 and 12 miles. (In this case, the energy release is estimated at a few kilotons.) Some fragments of a meteor like this typically fall to the ground, but only 1 percent to 5 percent of the original mass. ___3___ The last time one of this size hit Russia was in 2002. It was named the “Vitim bolide,” after the Vitim River Basin where the meteor fell.

Reports are still coming in about the brilliant meteor (technically known as a bolide) that slammed into the atmosphere over Russia, causing injuries that sent hundreds of people to the hospital. In any breaking story like this, not all of the information is reliable and details keep getting updated as more facts come in. Here’s the latest.

* The original mass of the rock that hit over Russia may be much larger than originally estimated. Calculations by astronomer Margaret Campbell-Brown at the University of Western Ontario in London, reported in the journal Nature, put its mass at 7,000 metric tons. At a density of 3 grams per cubic centimeter (typical of a stony meteorite), that means the parent body was about 15 meters (50 feet) wide. _____4______

* Most of the injuries and damage seem to have been caused by shock waves–sonic booms–from the meteor streaking through and breaking up in the atmosphere. ____5_____The bulk of the injuries seem to have come from shattered glass from broken windows.

* Just as scientists kept revising their estimate of the mass of the meteor, so they kept changing their estimates of how often objects of similar size strike our planet. _____6____Others stated once every decade. Now Nature is reporting that this was the largest meteor strike since the Tunguska event of 1908.

* At present, we have no way to detect meteors this size before they reach the Earth. ___7___And you can help collect statistics by keeping a watch on meteor events from the ground (the American Meteor Society offers some tips).

Date: 2015-02-28; view: 900