meteorites-asteroid-origins

New Study Reveals Majority of Earth's Meteorites Originate from a Singular Source

Introduction: The Allure of Fireballs

The sight of a fireball blazing across the sky captivates both children and adults, serving as a vivid reminder of Earth's place in a vast, dynamic universe.

Approximately 17,000  fireballs enter Earth's atmosphere each year, with many surviving the descent to the surface, offering scientists rare opportunities to study these extraterrestrial objects.

Meteorites: Understanding Their Origins

While scientists recognize that some meteorites originate from the Moon and Mars, most are asteroid-derived. Today, two studies in Nature take this understanding further. The research, led by Miroslave Brož from Charles University, Czech Republic, and Michaël Marsset from the European Southern Observatory, Chile, sheds new light on these cosmic origins.

The studies trace the origin of most meteorites to a few asteroid breakup events—and possibly even specific asteroids. This research deepens our understanding of the events that shaped Earth's history and the solar systems as a whole.

Defining Meteorites

A fireball is only termed a meteorite once it reaches Earth's surface. Meteorites are generally categorized into three types:

• Stony Meteorites
• Iron Meteorites
• Stony-Iron

Stony Meteorites:

Stony meteorites are classified into two categories.

1. Chondrites:

• The most prevalent type is chondrites, characterized by round structures formed from melted droplets. They account for 85% of all meteorites discovered on Earth.
• Most of these are classified as 'ordinary chondrites,' further divided into three broad categories—H, L, and LL—based on their iron content and the distribution of iron and magnesium in the primary minerals, olivine and pyroxene. These silicate minerals, also found in Earth's basalt, are fundamental to the solar system's structure.
• 'Carbonaceous Chondrites' form a unique class, characterized by high water content in clay minerals and organic compounds like amino acids. These chondrites have never been melted, offering direct samples of the primordial dust that gave rise to the solar system.

2. Achondrites:

The less prevalent type of stony meteorites are known as 'achondrites,' which lack the characteristic round particles of chondrites due to having undergone melting of planetary bodies.

The Asteroid Belt: An Insight into Origins

Meteorites primarily originate from asteroids.

The majority of asteroids are found within a dense belt situated between Mars and Jupiter. This asteroid belt comprises millions of asteroids influenced and organized by Jupiter's gravitational pull.

 Asteroid Dynamics

Interactions with Jupiter can disrupt asteroid orbits, leading to collisions. This generates debris that may coalesce into rubble pile asteroids, which subsequently develop their own dynamics.

Asteroids of this category were the targets of the recent Hayabusa and Osiris-REx missions, which returned with samples. These missions demonstrated the relationship between various asteroid types and the meteorites that fall to our planet.

Asteroid Classifications

• S-class asteroids: Similar to stony meteorites, are primarily located in the inner regions of the belt.
• C-class asteroids: Carbonaceous asteroids, akin to carbonaceous chondrites, are more prevalent in the outer regions.

The two studies published in Nature demonstrate a direct correlation between specific meteorite types and their corresponding source asteroids in the main belt.

New Research: Tracing Meteorite Origins

The two recent studies identify the origins of ordinary chondrite types within specific asteroid families, and likely down to individual asteroids. This research necessitates meticulous backtracking of meteoroid trajectories, observations of individual asteroids, and comprehensive modeling of the orbital evolution of their parent bodies.

Key Findings from the Studies

1. Ordinary Chondrites Origins: Miroslav Brož's study indicates that ordinary chondrites are derived from collisions between asteroids exceeding 30 kilometers in diameter, occurring no more than 30 million years ago.
2. Asteroid Families: Based on comprehensive computer modeling, the Koronis and Massalia asteroid families present optimal body sizes and spatial arrangements that contribute to material descending to Earth. Within these families, the asteroids Koronis and Karin are probably the key sources of H chondrites, whereas the Massalia (L) and Flora (LL) families are the main contributors of L- and LL- type meteorites.
3. Insights into L Chondrites: The study directed by Michaël Marsset offers further insights into the origins of L chondrite meteorites, confirming their like to Massalia.

Spectroscopic Data Analysis

By gathering spectroscopic data—characteristic light intensities that act as molecular signatures—from asteroids in the region between Mars and Jupiter, the research revealed that the composition of L chondrite meteorites found on Earth is remarkably similar to that of the Massalia family of asteroids.

Historical Collision and Fossil Meteorites

The researchers utilized computer modeling to indicate that a collision of asteroids around 470 million years ago was responsible for the formation of the Massalia family. Fortuitously, this collision also gave rise to a plethora of fossil meteorites found in the Ordovician limestones of Sweden.

Conclusion: The Significance of These Findings

In identifying the source asteroid bodies, these studies provide essential foundations for missions targeting the asteroids linked to the most frequent outer space visitors to Earth. Gaining insights into these source asteroids allows us to explore the events that have shaped our planetary system.

Source

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