HOW TO KILL AN ASTEROID

Big asteroids rarely strike our planet, but smaller ones not so rarely, and scientists are worrying.

Science journalist Andrews, author of Super Volcanoes, writes that an asteroid blew up over Chelyabinsk, a Russian city of 1.2 million, in 2013. Disintegrating before reaching the ground, it produced a vivid flash and deafening explosion that broke windows and damaged thousands of buildings. More than a hundred citizens were hospitalized. The explosion, equal to that of 500,000 tons of TNT, was caused by an asteroid 60 feet wide. History buffs remember the 1908 Tunguska meteor, which destroyed 800 square miles of remote Siberia, flattening 80 million trees with a blast equivalent to that of 12 million tons of TNT. It was 160 feet across. Surprise asteroids thrill movie audiences, but astronomers have detected most of the big ones. On the other hand, readers may be startled to learn that of the several hundred thousand Tunguska-size asteroids that astronomers call “near-Earth objects (NEOs)” (they’re also called “city killers”) thought to exist, only 7 percent have been found. Having set the scene, Andrews describes a NASA mission, DART, to send a spacecraft crashing into a distant NEO to shift its orbit. Launched in November 2021, it successfully completed its mission the following September, proving that this could be done. Andrews describes other missions to asteroids and comets, as well as ongoing NASA efforts at planetary defense, although readers may be dismayed to learn these are not a priority. A high-tech satellite, NEO Surveyor, designed to detect the mass of undetected asteroids, was proposed in the early 2000s, approved after many delays, and scheduled to launch by 2028, but that date became uncertain when its budget was cut. A member of the “science is boring” school, Andrews writes breezy prose peppered with flippant asides, jokes, and apologies for technical terms, but he has done his homework.

A skillful review of NASA efforts to save the Earth.