An image captured by the GOES-16 satellite shows a flash (purple) most likely caused by a bolide (exploding meteor) over New Hampshire on Oct. 10, 2021.
Credit: NOAA

A mysterious boom rattled houses, shook the ground, and frightened pets in southern New Hampshire around 11:30 a.m. on Sunday, October 10. Curious people in the Granite State took to the internet to find the cause. Was it an earthquake, an aircraft, a single thunderclap, a spaceship, or a meteor? There was nothing in the news about it, so one observer called the fire department, which also did not have any answers. Around 400 residents shared their observations on volcanodiscovery.com, an online forum where people report seismic activity (vibrations from earthquakes). What caused the boom?

While earthquakes do occur in the area of New Hampshire, the United States Geological Survey announced that there were no earthquakes in all New England on Sunday. The Geological Survey is a federal agency tasked in part with monitoring such hazards as earthquakes and volcanoes.

Ruling out an earthquake, many people kept researching. One cause of confusion was that even though there was an audible (able to be heard) boom and physical thud, there was no damage reported. Was it a powerful military plane? The Federal Aviation Administration announced there was no unusual military flight activity over the state. One concerned resident theorized that the sound came from the recently established New Boston Space Force Station, previously an air force base.

Meteorologists said the mystery blast was most likely a sonic boom caused by a meteor. A meteor appears when a piece of matter enters Earth’s atmosphere from space at high speed, causing it to heat up. A fireball is a meteor that burns brightly as it plunges through the atmosphere. If the fireball explodes at the end of its path, it is called a bolide.

Greg Cornwell, a meteorologist for the National Weather Service, said that a suspicious spot appeared in images from the weather satellite GOES-16, which in part maps lightning strikes, around the same time people reported the boom. Weather satellite images generally pick up storms and other weather patterns. Although it was overcast that morning, there were no thunderstorms to explain the blip. Bolides and fireballs have in the past appeared as false storms in satellite images. Cornwell also explained that this time of year is known for meteor showers.

Many experts considered it likely that a meteor explosion produced the mysterious boom. However, to officially pin the blast on a meteor, scientists need a direct eyewitness account or video evidence. No solid eyewitness account or video evidence has been brought forward, so residents may have to settle for a hunch.

October 13, 2017

Yesterday, on Thursday, October 12, a house-sized asteroid buzzed Earth, passing within the orbit of the moon and uncomfortably close to hundreds of orbiting communications and weather satellites. Officials at the United States National Aeronautics and Space Administration (NASA) insisted there was never any danger of a collision. They first discovered the space rock, called 2012 TC4, five years ago and have been following it ever since. The close shave by TC4 posed no threat, but it did provide NASA with an opportunity to test systems that detect orbiting objects and to develop plans to respond to a potentially catastrophic impact.

This illustration depicts the safe flyby of asteroid 2012 TC4 as it passes by Earth on Oct. 12, 2017. Credit: NASA/JPL-Caltech

Technicians from NASA and the European Space Agency’s Near-Earth Object program measured TC4 to be about 50 to 100 feet (15 to 30 meters) in diameter. It is traveling through space at about 16,000 miles (25,800 kilometers) per hour. At its closest, it will pass by southern Australia a mere 27,300 miles (44,000 kilometers) above the surface, just beyond the 22,400-mile (36,000-kilometer) plane of Earth’s most remote geosynchronous (fixed-orbit) satellites.

This illustration shows the path of asteroid 2012 TC4 as it passes within the moon’s orbit of Earth on Oct. 12, 2017. Credit: NASA/JPL-Caltech

Technicians at the space agencies determined that TC4 makes an elongated orbit around the sun every 609 days. They calculate that TC4 will pass close to Earth again in 2050 and 2079. For now, the calculations show that there is no danger of TC4 striking Earth. However, should TC4’s orbit be deflected by even a small amount, the chances of an impact could increase. Officials say there is a 1-in-750 chance that TC4 could strike Earth sometime after 2050. Those are long odds, to be sure, but NASA scientists continue to track TC4 nonetheless, as well as 12 other asteroids with a greater risk of impact.

Scientists know that Earth has been struck by asteroids and meteors repeatedly over the past 4.5 billion years. NASA experts estimate that objects the size of TC4 fly past Earth about three times per year. They point out, however, that the chances of a serious asteroid impact anytime soon are remote. But even the experts are occasionally taken by surprise. The Chelyabinsk meteor, a chunk of rock similar in size to TC4, fell into Earth’s atmosphere and exploded over the city of Chelyabinsk in southeastern Russia on Feb. 15, 2013. The impact frightened thousands of people and took NASA and other space-observing agencies by surprise. They did not see that one coming.

February 25, 2016

On February 6, a large fireball fell toward Earth and exploded in the atmosphere. Fortunately, it exploded over the Atlantic Ocean, some 600 miles (970 kilometers) off the coast of Brazil. Had it disintegrated over a populated area, it could have caused many injuries and deaths.

This photograph shows the Chelyabinsk meteor streaking through the sky above Chelyabinsk, Russia, on Feb. 15, 2013. The small asteroid was about 56 to 66 feet (17 to 20 meters) wide. Credit: M. Ahmetvaleev/NASA/JPL-Caltech

A meteor is a streak of light that appears in the sky. The brightest meteors are known as fireballs or bolides. A meteor appears when a piece of matter enters Earth’s atmosphere from space at high speed. Such a piece of matter is called a meteoroid. Most meteoroids that cause visible meteors are smaller than a pebble. As the meteoroid collides with the air, it is heated so that it glows, creating a shining trail of hot gases. Most meteoroids break apart in a second or less. Some fireballs explode as they descend through the atmosphere, sending powerful shockwaves toward Earth.

The February 6 fireball was the largest to reach Earth since the Chelyabinsk meteor exploded over southeastern Russia almost exactly three years earlier. That fireball passed over the city of Chelyabinsk and was recorded on video by dozens of people, giving scientists and the public alike a detailed view of the strike. The shockwave from the explosion damaged thousands of buildings and injured over 1,500 people, mostly with flying glass from broken windows. Scientists think the meteoroid was about 65 feet (20 meters) across and weighed more than 11,000 tons (10,000 metric tons).

An even larger bolide fell in the Tunguska River region of central Russia in 1908. Exploding over a forested area, the blast flattened thousands of trees and damaged the few structures in the area. Because it struck in such a sparsely populated region, only a few injuries and no deaths were reported.

Scientists are studying these strikes to improve their ability to detect potential meteoroids that could threaten major population centers on Earth. Researchers are also investigating ways to destroy would-be meteors or alter their paths.

Other World Book articles

• Astronomy (1983) – A Back in Time article
• Astronomy (1984) – A Back in Time article
• Astronomy (2013) – A Back in Time article
• The Perils of Earth-Buzzing Meteors – A Special Report
• When Worlds and Comets Collide – A Special Report

August 27, 2013

Dust particles from the meteor that exploded over the Russian city of Chelyabinsk in western Siberia on February 15 formed a belt that circled the Northern Hemisphere for months, NASA scientists have found. The scientists, working out of the Goddard Space Flight Center in Greenbelt, Maryland, said that within four days of the explosion, the faster, higher part of the belt had encircled the Earth and returned to Chelyabinsk. Although larger pieces of the belt slowly lost speed and altitude over time, small, light particles remained in the stratosphere for at least three months. The scientists mapped the dust belt using data from the NASA-NOAA Suomi National Polar-orbiting Partnership satellite and computer simulations of atmospheric circulation patterns.

The higher faster particles (red) in a dust plume created by the explosion of a meteor over Siberia circled the Northern Hemisphere within only four days. (NASA Goddard's Scientific Visualization Studio)

The meteor, which measured 59 feet (18 meters) across, created a powerful sonic boom as it slammed into Earth’s atmosphere at 41,600 mph (18.6 kilometers per second) and exploded at an altitude of 14.5 miles (23.3 kilometers) above Chelyabinsk. The explosion injured more than 1,000 people and shattered windows, dishes, and television screens over a large area near the city. Numerous videos taken by residents captured the fireball as it blazed across the sky and the ground-shaking shockwave that followed.

Additional World Book articles:

• When Worlds and Comets Collide (a special report)
• What Has Caused Mass Extinctions (a special report)

April 27, 2012

A giant fireball, a meteor, lit up the sky above the Sierra Nevada Mountains near Sutter’s Mill, California, early on April 22. Seen from as far away as Sacramento, the state capital, and Reno, Nevada, the fireball was caused by a meteoroid, a piece of primordial matter from space.

A meteoroid becomes visible when it enters Earth’s atmosphere from space at very high speed. As the meteoroid collides with the atmosphere, friction causes it to heat up so that it glows, creating a shining trail of hot gases. Most meteoroids are smaller than a pebble and break apart in a second or less.

A meteor appears in the sky when an object called a meteoroid enters the atmosphere from space. (World Book illustration by Greg Maxson)

Scientists believe that the meteoroid that hit the atmosphere with a loud explosion over California probably weighed about 154,300 pounds (69,990 kilograms) and was as large as a minivan. They calculated that it hit the atmosphere with about one-third the explosive force of an atomic bomb. The loud boom heard as the meteoroid streaked across the sky was caused by the speed with which the rock entered the atmosphere. Scientists estimate the meteoroid was traveling up to 44,000 miles (80,000 kilometers) per hour–many times faster than the speed of sound–when it hit the atmosphere. This caused the gigantic sonic boom heard across two states.

Thousands of meteorites rained down over hundreds of square miles as the fireball broke apart in the sky. Meteorites are meteoroid fragments that reach the Earth’s surface intact. By midweek, collectors had found several meteorites weighing about 1/3 ounce (10 grams) each. After examining the fragments, scientists determined that the large meteoroid was a rare, carbon-rich type known as a carbonaceous chondrite. This type of meteorite is made up of the same material from which the planets formed and dates to the very beginnings of the solar system more than 4 billion years ago. Scientists hope to find even more fragments of this rare meteor event.

Additional articles in World BooK:

• Meteor Crater
• Shoemaker, Eugene Merle
• Stones from Space (a Special Report)