Ivuna, CI1

Type-1 chondrites are fairly rare, partly because they are so fragile.  Atmospheric entry often results in very high mass loss for these kinds of meteorites, and, once they land, they don’t last long before being weathered into mud or dust.

CI1 chondrites are important meteorites for a few reasons.  Type-1 chondrites have often experienced little to no thermal alteration (heating/melting), so they preserve rare inclusions like pre-solar grains.  Pre-solar grains are microscopic mineral grains that formed either with the convective outer layer of large stars, or within the nebula(e) that provided the starting material (gas and dust) for everything in our solar system.

Helix planetary nebula
The Helix planetary nebula, surrounded by an expanding ring of gas and dust. Dust like this was incorporated into many meteorites, but is preserved only in a few rare types that have escaped heating, like CI1 chondrites.

 

Unfortunately, these meteorites have undergone significant aqueous alteration, which has erased much of their original chondritic texture. But, that same alteration has catalyzed a number of interesting chemical reactions. When olivine and other ultramafic minerals are exposed to water, certain chemical reactions start to take place. These reactions create heat, hydrogen, methane, ammonia, and other compounds and molecules important for life.

 

serpentinite
A plane-polarized image of a thin section of harzburgite (a rock made of olivine and pyroxene), partially altered to veins of serpentine minerals. Image courtesy of Evelyn Mervine, at http://blogs.agu.org/members/emervine/

Here are a few solid papers on the topic:

Serpentinization and Its Implications for Life on the Early Earth and Mars, by Schulte et al., 2006.

H2-rich fluids from serpentinization: Geochemical and biotic implications, by Sleep et al., 2004.

Hydrothermal vents and the origin of life, by Martin et al., 2008.

Carbonaceous chondrite phylosilicates and light element geochemistry as indicators of parent body processes and surface conditions, by T. Bunch and S. Chang, 1980.

As a result of these wet reactions — and high energy solar radiation, these meteorites often contain complex organic molecules and are hypothesized to have played a role in the formation of life on Earth ~4.2-4.4 billion years ago.  CI1 chondrites in particular contain some of the highest water and organic molecule concentrations of any known meteorites and are often compared to cometary material.

Evidence for aqueous activity on comet 81P/Wild 2 from sulfide mineral assemblages in Stardust samples and CI chondrites, by Berger et al., 2010.

In short, they’re very interesting rocks and they contain many complex features, many of which we don’t understand quite yet.  This specimen weighs only 0.49 grams, but it likely contains a few thousand pre-solar grains!

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