Chondrites: The Most Primitive Rocks in the Solar System

Chondrites give geologists insights on the makeup of the early solar system. Geologists are driven by understanding how the Earth came to be what it is today. Chondrites formed at the time o

Introduction

Chondrites are the most primitive rocks in the solar system. Chondrites are stony (non-metallic) meteorites that have not been modified due to melting or differentiation of the parent body. Chondrites are formed when dust and small grains that originated from the early solar system accreted to form asteroids. Chondrites represent 86% of meteorites that fall to Earth. An important diagnosing feature of chondrites is the presence of chondrules. Chondrules are millimeter sized round inclusions made primarily of olivine and pyroxene, and chondrules make up 20-80% of the volume of most chondrites. Chondrites are important to geochemistry because chondrites give insight on the composition and age of the early solar system, the presence of water on Earth, and possibly the origin of life.

Background

Chondrites were made by the accretion of particles of dust present in the primitive Solar System which gave rise to asteroids over 4.55 billion years ago (SOURCE). These asteroid parent bodies of chondrites were small to medium sized asteroids that were never large enough to go through melting and planetary differentiation like Earth. Further evidence of age is shown through the abundance of non-volatile elements in chondrites which is similar to that found in the atmosphere of the Sun and other stars in our galaxy.[10] Even though chondritic asteroids never became hot enough to melt based upon internal temperatures, many of these asteroids did reach high enough temperatures to experience significant thermal metamorphism in the interior. T...

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...carbon chains, rings, and amino acids.

Chondrules make up a large portion of chondrites. The millimeter-sized spherical objects originated as molten droplets in space. Most chondrules are rich in olivine and pyroxene. Chondrites also contain refractory inclusions (including Ca-Al Inclusions), which are among the oldest objects to form in the solar system, particles rich in metallic Fe-Ni and sulfides, and isolated grains of silicate minerals. The remainder of chondrites consists of fine-grained dust, which is either present in the matrix of the rock or forms rims or mantles around individual chondrules and refractory inclusions[11]. The geologic and cosmologic communities generally accepts that these spheres were formed by the action of a shock wave that passed through the Solar System, although there is little agreement as to the cause of this shock wave.[12]