Astro Bob: Booming fireball drops meteorites near Natchez
Hunters find meteorites after a brilliant fireball streaked over Mississippi on April 27.
On April 27 at 8:03 a.m. Central Daylight Time, as many drove to work and school, a dazzling, fast-moving fireball seared the sky over Mississippi, producing multiple sonic booms. More than 60 eyewitnesses across that state, Louisiana, Alabama and Arkansas reported hearing loud explosions as the object burst onto the scene, momentarily shining nearly as bright as the sun.
One observer likened it to a welder's torch. After several, flickering bursts, the fireball left a white smoke trail that lingered for several minutes. Even the GOES 16 and 17 satellites captured the meteor's flash from geostationary orbit 22,200 miles (37,500 km) away. Check out this brief weather-cam video capture .
According to NASA's Meteorite Falls website , signatures of falling meteorites were found in imagery from at least four nearby weather radars in the NEXRAD weather radar network operated by NOAA. Falling in a nearly vertical column, meteorites showed up in at least 11 radar sweeps, with the first signature recorded at 7 miles (11.2 km) altitude.
As soon as the news broke, meteorite hunters beat a path to the town of Cranfield and surrounds, located 16 miles east of Natchez, where radar data indicated space rocks might be recovered. On Sunday, May 1, Roberto Vargas shared the news of the first meteorites recovered. He and two other eagle-eyed hunters turned up three extraterrestrial stones after searching through grass and brush. Vargas' fragment hit a road and "broke into a bunch of pieces." It weighed 5.3 ounces (150 grams).
Vargas describes the strewn field — the path along which the meteorites fell — as dense with vegetation and difficult to hunt in the hot and humid conditions.
Close up photos of the meteorite show rich black fusion crust — formed when the outer 1-2 millimeters of an incoming meteoroid (the name for a space rock when it's still in space) is heated and melted during its atmospheric plunge. In contrast, the interior is pale and "brecciated." Breccia (BREH-chee-uh) is made of fragmented rock welded together by heat and pressure, a good sign that its "parent" asteroid suffered an impact with another asteroid in the distant past.
Scientists estimate that the Mississippi meteoroid was about a foot across, weighed about 90 pounds and struck the atmosphere at 55,000 miles per hour (8,850 km/hour). The explosion released as much energy as three tons of TNT.
Moving this swiftly not only heats the exterior of the object, causing it to glow, but also ionizes the air to create the bright streak of light we know as a meteor.
Once the meteoroid decelerates to 4,500-9,000 mph (2-4 km/second), which occurs at around 12-19 miles (20-30 km) altitude, it enters what's called dark flight. During this phase, a space rock is no longer visible but can still travel long distances. Eventually, its speed drops until it's in free fall and drops to the ground.
Often, incoming meteoroids slam into the air and turn to dust, but occasionally they survive and are recovered. Traditionally, meteorite hunters and scientists have used eyewitness reports to estimate the likely location of a meteorite fall, but these days, weather radar has become an effective tool because it can actually "see" falling objects and better pinpoint where we might seek them.
How exciting to welcome another cosmic traveler to Earth!
"Astro" Bob King is a freelance writer for the Duluth News Tribune.