In the pinball world of asteroids, mud ball meteorites avoid collision

In April 2019, a rare primitive meteorite fell near the town of Agas Zacas in northern Costa Rica. Articles published online in Magazine Meteorological and Planetary ScienceAn international researcher described the situation in autumn and showed that mud ball meteorites are not necessarily weak.

“27 kilograms of rock were recovered, making this the biggest fall since 1969 that fell near Murchison, Australia, near Murchison, Australia,” said Peter Jenniskens, Meteor astronomer at Seti Institute.

In 1969, researchers prepared to learn about the moon rocks and eagerly trained the instrument on another rock in space.

“Recovery for humans is also a small step for humans, but it is a huge leap for meteors,” said Gerardo Soto, a geologist at the University of San Jose at Costa Rica, explaining in the words of Neil Armstrong. “Since then, 76 papers have been written about this meteorite.”

Jenniskens collaborated with Soto to investigate the new fall.

Soto added: “The fall of Aguas Zarcas is huge news in the country. No other fireball has been widely reported in the past 150 years, and then stones have been restored on the ground like Costa Rica.”

The team’s analysis of the camera lens showed that the rock entered the Earth’s atmosphere at a speed of 14.6 kilometers per second from the WNW direction at a nearly vertical angle. The strong collision with the atmosphere melts (absorbs) most of the rocks, but surprisingly there are signs of fragmentation.

“It penetrates deep into the Earth’s atmosphere until the surviving mass shatters 25 kilometers above the surface of the ground, and it produces a bright flash, and satellites in orbits detect bright flashes.”

Nature is friendly to this meteorite, as the fall occurs at the end of an unusually long dry season in Costa Rica.

“Aguas Zarcas Fall produces fusion stones of various shapes,” said Laurence Garvie, co-author and meteorologist at the Buseck Meteorite Research Center at Arizona State University. “Some stones have a beautiful blue iridescent to the fusion shell.”

Many stones are uninterrupted as they land on relatively soft jungle and turf surfaces. The researchers were surprised by the abnormal shape of many of the rocks caused by ablation, without the relatively flat surfaces caused by secondary debris.

“Other meteorites of this type are often described as mud balls because they are rich in water, which obviously does not mean they are weak,” Jenniskens said.

The research team now believes that Aguas Zarcas is strong because it avoids collisions in space and does not weaken the cracks of many meteorites.

“The last collision of this rock was 2 million years ago,” said Cosmochemist Kees Welten of the University of California, Berkeley.

He and his team measured how long the rock was exposed after it fell from the larger asteroids.

“We know other meteorites similar to Murchison broke out around the same time and may have broken down in the same event, but recently most people have broken it.”

The team determined that when the rock hits the Earth’s atmosphere, the diameter of the rock is about 60 cm. From its path through the atmosphere, the team traced the meteorites back to the asteroid belt.

“We can say that this object comes from a lower asteroid in the asteroid belt with a smaller planet,” Jenniskens said. “After letting go, it took two million years to hit the tiny target of Earth, and has been avoiding breakage.”

Because the rock is strong and enters at a steep angle, a relatively large portion of its mass survives on the ground.