Mudball Meteorite Spent 2 Million Years Dodging Collisions – Until Eart

One of the most extensively studied space rocks has recently surprised scientists once again. The “mudball meteorite” Aguas Zarcas, which spent two million years in orbit without colliding with any other objects (or sustaining any damage if it did), challenges the conventional view of the “fragile” carbonaceous chondrite class to which it belongs.

Public Fascination and Auctioned Doghouse Incident

This meteorite has fascinated the public since it streaked through Earth’s atmosphere in April 2019, breaking apart and falling over Costa Rica. In 2022, a doghouse hit by one of the meteorite’s fragments, leaving a seven-inch (18 cm) hole in the roof, was auctioned for nearly $50,000. (Fortunately, Roky, the German shepherd who had been inside the doghouse at the time, was unharmed and likely enjoyed a kennel upgrade after the auction.)

“Twenty-seven kilograms [60 pounds] of rocks were recovered, making this the largest fall of its kind since similar meteorites fell near Murchison, Australia, in 1969,” said Peter Jenniskens, a meteor astronomer at the SETI Institute and NASA Ames Research Center.

Geologist Gerardo Soto of the University of Costa Rica, San José, noted that researchers have since published seventy-six papers about this meteorite. The Aguas Zarcas fall was a huge event in Costa Rica. No other fireball has been as widely reported and then recovered as stones in the country over the past 150 years.

Tracking the Meteorite’s Journey Through Space

Jenniskens and Soto collaborated on a new study that traced the meteorite’s journey using satellite data, radar, security cameras, and dashcams.While scientists have well documented its arrival on Earth, its origin—likely from an asteroid in the outer asteroid belt—remains intriguing.

In the case of the CM2 carbonaceous chondrite meteorite, the “M” refers to a subgroup named after the Mighei rock, which landed in Ukraine in 1889, and the “2” indicates the extent to which its composition has changed due to water and heat, on a scale from one to six.This categorization indicates that the meteorite underwent moderate alteration due to water, but not heat.

People often call carbonaceous chondrite meteorites “mudballs” because they contain carbon, organic material, and water-bearing minerals, which make them vulnerable to breaking apart either in space or when they enter Earth’s atmosphere. Meteorites like Sutter’s Mill and Flensburg had very little recoverable material, reinforcing the idea that these rocks are fragile.

Jenniskens said that people often describe other meteorites of this type as mudballs due to their water-rich minerals.However, this does not mean they are inherently weak.

Aguas Zarcas: A Rare Meteorite That Survived Space

While Aguas Zarcas did break apart at an altitude of around 25 km (15.5 miles) above Earth’s surface, it didn’t shatter into tiny pieces like many others of its kind. Instead, it left behind large, intact fragments. By measuring its exposure to cosmic rays, essentially dating it, scientists, along with cosmochemist Kees Welten from the University of California, discovered that it likely drifted through space for over two million years without any damage. This finding contradicts previous assumptions about carbon-rich meteorites, which typically suffer collisions and explode into smaller fragments before reaching Earth’s surface.

The last collision experienced by this rock occurred two million years ago, Welten said.

The team also measured the radioactive elements in the 146-gram (5.15-ounce) Aguas Zarcas fragment, which revealed that a significant amount of time had passed since cosmic rays last exposed its inner layers—essentially, since it broke off from its asteroid two million years ago.

New Insights into Carbonaceous Chondrites

We know of other Murchison-like meteorites that likely broke off around the same time, possibly in the same event, Welten added, but most of them broke up much more recently.

The research team also determined that the meteorite was about 60 cm (23.6 inches) in diameter when it entered Earth’s atmosphere, originating from a much larger asteroid in the outer regions of the asteroid belt.

Jenniskens said that we can tell this object came from a larger asteroid in the lower part of the asteroid belt, probably from its outer regions. After its release, it took two million years to reach Earth’s tiny target, all the while avoiding any significant damage.

These findings provide fresh insight into carbonaceous chondrites, which scientists consider some of the most primitive materials in the solar system. This new research suggests that Aguas Zarcas might deserve a new, more fitting name than the fragile-sounding mudball meteorite.

Read the original article on: New Atlas

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