ORIGINS OF THE SOLAR SYSTEM

METEORITES CONTAIN THE OLDEST MATERIAL IN THE SOLAR SYSTEM AND REVEAL CLUES TO THE FORMATION OF OUR SUN AND PLANETS.

THE BLUE-WHITE FIREBALL STREAKED ACROSS THE DARK SKIES above northern Mexico shortly after one o'clock in the morning on February 8, 1969. Residents of the Mexican town of Pueblito de Allende watched with astonishment as the glowing object approached and, with a tremendous blast, exploded into thousands of pieces that rained down across the region.

Although no one suspected it at the time, the Allende fall would revolutionize the science of meteorites. Suddenly, scientists had two tons of a previously rare type of meteorite available for study. Allende and meteorites like it contain the oldest known material formed in the solar system-and provide clues to how our solar system evolved into the Sun, planets, asteroids and comets we know today.

LOCATING ALLENDE

When a meteorite like Allende breaks apart in the atmosphere, the resulting fragments scatter across the ground. The oval-shaped area where the pieces fall is called a strewn field. The Allende strewn field in the northern Mexican state of Chihuahua covers an area roughly twice the size of Manhattan—and is one of the largest ever studied.

As meteorite fragments travel through the atmosphere, they are slowed by friction and eventually drop to the ground. Larger fragments tend to travel farther before falling to Earth because they take longer to slow down than smaller fragments. The biggest chunks of Allende have been found at the northern end of the strewn field.

AN EXPLOSION OF STONES

Before Allende fell to Earth, it probably weighed around four tons—roughly the weight of an Asian elephant. But meteorites travel through the atmosphere so rapidly—sometimes 15 kilometers a second (34,000 miles an hour) or more—that the surfaces heat up and start to melt. Most meteorites then shatter in a burst of light.

Many people in northern Mexico heard the loud explosion of Allende breaking into thousands of small pieces like the ones shown. Immediately after Allende fell, residents and collectors began gathering pieces from across the region. In the days, weeks and months after the fall, more than half the original mass was recovered.

Thousands of pieces of the Allende meteorite fell across rural Mexico early on February 8, 1969. The same day, residents of the small town of Pueblito de Allende brought the first samples to a local newspaper, and an article about the dramatic shower appeared that evening. Meteorites are typically named for the place they are found, so scientists refer to this meteorite as Allende.