- A 100,000 pound meteorite explodes in a fireball over northern California. April 22, 2012, at 8:00 AM a meteorite exploded in the atmosphere over El Dorado County, California. The kinetic energy of mass times velocity squared was equivalent to a 4,000 ton bomb. The explosion was heard as far away as Washington state. The fiery streak of light could be seen across northern Nevada and California. Lucky it exploded before hitting the surface.
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- The meteorite weighed 100,000 pounds, about the size of a mini-van. There have been 77 fragments recovered to date, but, the total weight of the pieces is only 2 pounds. The largest was ½ pound (0.45 lb.) with the next largest only 0.2 lb.
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- The meteorite is called “Sutter’s Mill meteorite“. Most of the 77 fragments were found around the towns of Lotus, and Coloma, along the American River. One piece was found in the parking lot of the Marshall Gold Discovery State Historical Park.
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- The fragments were the most pristine samples ever collected. Their composition was a rare type of carbonaceous chondrite. These minerals were formed 4.5 billion years ago when the Solar System was first born. Some 40,000 meteorites have been recovered. Only 1,103 are documented with analysis. Carbonaceous chondrite represents 4.6% of these. Some meteorites contain 3 to 22% water which means their temperatures never exceeded 200C.
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- Doppler weather radar tracked the meteorite as it streaked through the atmosphere. Astronomers believe this meteorite came from the asteroid belt between Jupiter and Mars. They believe it had a highly eccentric orbit that swings close to the Sun and close to Jupiter on its return. It is also believed that this rock broke off a bigger rock asteroid some 15,000 to 19,000 years ago. It is the fastest meteorite ever recorded traveling 28,600 meters per second, 65,000 miles per hour.
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- One crystal-like mineral called “Oldhamite” was found that formed during the very first years of the Solar System’s evolution. Most meteorite are composed of silicates, oxides and sulfates.
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- Oldhamite is very reactive and would have disappeared very quickly once on the ground. Fortunately, some fragments were recovered and preserved within hours of impact. The next days’ s rain would have erased all evidence of the Oldhamite. This evidence told astronomers that this asteroid originally formed closet to Earth and Venus rather than close to Jupiter. It’s history indicates wide travels throughout the Soar System. Even diamonds were found in some of the fragments. There was even evidence of flowing water that likely existed on the larger asteroid.
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- One theory of the water on Earth is that it was delivered by asteroids during an era of bombardments. The early Earth was too hot and volcanic to have retained any liquid water. Our oceans had to have arrived later in Earth’s evolution.
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- The Solar System began as a Solar Nebula disc-shaped composed of gas and dust left over from the Sun’s formation 4.6 billion years ago. It becomes an accretion disk from which planets, asteroids, and comets formed. The grains of dust clump together and merge through collisions growing a centimeter per year over millions of years.
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- An astronomical unit ( AU) is the distance between the Earth and the Sun, 93 million miles. Inside 4 AU only high melting point materials could survive, like nickel, iron, and aluminum and silicates. All water or methane would be evaporated. The rocks that made Mercury, Venus , Earth, and Mars comprise only 0.6% of the mass of the Solar Nebula.
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- Planet collisions and orbits through the gas and dust cause a loss of angular momentum allowing planets to gradually migrate out from the Sun to new orbits.
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- The gas giants Jupiter, Saturn, Uranus and Neptune formed further out from the Sun, beyond 5 AU, the Frost Line, where water would freeze. These gas giants comprise 99% of the mass orbiting the Sun.
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- After 10 million years the Sun’s solar wind cleared away all the Solar Nebula gas and dust blowing it into interstellar space, ending the growth of the planets.
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- To learn more about these asteroids we can not wait for them to explode in our atmosphere. Future space missions are to send a rocket to land on an asteroid and bring samples back to Earth for study. We hope to learn much more about the birth of the Solar System with these missions. 1,000’s of other solar systems have been discovered. To learn about their evolution we need to know how are unique is ours? How likely is the evolution of life on these other solar systems. Are we alone?
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- There was a meteorite discovered in Morocco last December that was identified as coming from Mars. By measuring the ratios of oxygen isotopes geologists can trace volcanic rocks back to the magmas that formed them. This meteorite was a rock on the surface of Mars for hundreds of millions of years before it was blasted into space.
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- The type of rocks that could tell us more about climate, habitability, and life are sedimentary rocks. Unfortunately they are too soft to become meteorites. When asteroids hit Mars, blast rocks in to space, survive the journey to Earth, enter the atmosphere, and land on the surface they have to be very hard rocks. The Sutter’s Mill Meteorite is one of those very hard rocks. An announcement will be made shortly, stay tuned.
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