Discovery of the source of the most common meteorites

July 10, 2008
(Right) Comparison of the spectrum of asteroid (1270) Datura with the spectrum of the Fayetteville meteorite. (Left) Pictures of the Fayetteville meteorite (© Arkansas Center for Space and Planetary Sciences, University of Arkansas).

Astronomy & Astrophysics is publishing the first discovery by T. Mothé-Diniz (Brazil) and D. Nesvorný (USA) of asteroids with a spectrum similar to that of ordinary chondrites, the meteoritic material that most resembles the composition of our Sun. Most of the meteorites that we collect on Earth come from the main belt of asteroids located between Mars and Jupiter [1].

They were ejected from their asteroidal “parent body” after a collision, were injected into a new orbit, and they finally felt onto the Earth. Meteorites are a major tool for knowing the history of the solar system because their composition is a record of past geologic processes that occurred while they were still incorporated in the parent asteroid.

One fundamental difficulty is that we do not know exactly where the majority of meteorite specimens come from within the asteroidal main belt. For many years, astronomers failed to discover the parent body of the most common meteorites, the ordinary chondrites that represent 75% of all the collected meteorites.

To find the source asteroid of a meteorite, astronomers must compare the spectra of the meteorite specimen to those of asteroids. This is a difficult task because meteorites and their parent bodies underwent different processes after the meteorite was ejected. In particular, asteroidal surfaces are known to be altered by a process called “space weathering”, which is probably caused by micrometeorite and solar wind action that progressively transforms the spectra of asteroidal surfaces. Hence, the spectral properties of asteroids become different from those of their associated meteorites, making the identification of asteroidal parent body more difficult.

Collisions are the main process to affect asteroids. As a consequence of a strong impact, an asteroid can be broken up, its fragments following the same orbit as the primary asteroid. These fragments constitute what astronomers call “asteroid families”. Until recently, most of the known asteroid families have been very old (they were formed 100 million to billions of years ago). Indeed, younger families are more difficult to detect because asteroids are closer to each other [2]. In 2006, four new, extremely young asteroid families were identified, with an age ranging from 50000 to 600000 years. These fragments should be less affected than older families by space weathering after the initial breakup. Mothé-Diniz and Nesvorný then observed these asteroids, using the GEMINI telescopes (one located in Hawaii, the other in Chile), and obtained visible spectra. They compared the asteroids spectra to the one of an ordinary chondrite (the Fayetteville meteorite [3]) and found good agreement, as illustrated on Fig. 1.

This discovery is the first observational match between the most common meteorites and asteroids in the main belt. It also confirms the role of space weathering in altering asteroid surfaces. Identifying the asteroidal parent body of a meteorite is a unique tool when studying the history of our solar system because one can infer both the time of geological events (from the meteorite that can be analyzed through datation techniques) and their location in the solar system (from the location of the parent asteroid).

Notes:

[1] There are only a few exceptions, including the example of the famous meteorites coming from Mars.

[2] After the primary asteroid is disrupted, the fragments move away from each other. The older the collision, the greater the distance between fragments.

[3] Meteorites are named for the place they were collected. The Fayetteville meteorite fell near Fayetteville, Arkansas, on December 26, 1934.

Citation: Visible spectroscopy of extremely young asteroid families, by T. Mothé-Diniz and D. Nesvorný, Astronomy & Astrophysics Letters, 2008, volume 486-2, pp. L9-L12

Source: Astronomy & Astrophysics

Explore further: Space Kombucha in the search for life and its origin

Related Stories

Space Kombucha in the search for life and its origin

July 30, 2015

You might know it as a drink for hipsters or as an ancient brew drunk for centuries in Eurasia, but the culture that ferments sugary tea into Kombucha is going around the world. Bolted to the outside of the International ...

Vesta's potassium-to-thorium ratio reveals hot origins

July 23, 2015

Studies of materials on the surface of Vesta offer new evidence that the giant asteroid is the source of howardite, eucrite and diogenite (HED) basaltic meteorites, supporting current models of solar system evolution and ...

The difference between asteroids and meteorites

June 3, 2015

Asteroids, meteors, and meteorites … It might be fair to say these rocks from space inspire both wonder and fear among us Earthlings. But knowing a bit more about each of them and how they differ may eliminate some potential ...

What is a terrestrial planet?

July 2, 2015

In studying our solar system over the course of many centuries, astronomers learned a great deal about the types of planets that exist in our universe. This knowledge has since expanded thanks to the discovery of extrasolar ...

What is the Kuiper Belt?

June 17, 2015

Dr. Mike Brown is a professor of planetary astronomy at Caltech. He's best known as the man who killed Pluto, thanks to his team's discovery of Eris and other Kuiper Belt Objects. We asked him to help us explain this unusual ...

Recommended for you

Tracking a mysterious group of asteroid outcasts

August 4, 2015

High above the plane of our solar system, near the asteroid-rich abyss between Mars and Jupiter, scientists have found a unique family of space rocks. These interplanetary oddballs are the Euphrosyne (pronounced you-FROH-seh-nee) ...

Dense star clusters shown to be binary black hole factories

July 29, 2015

The coalescence of two black holes—a very violent and exotic event—is one of the most sought-after observations of modern astronomy. But, as these mergers emit no light of any kind, finding such elusive events has been ...

Image: Hubble sees a dying star's final moments

July 31, 2015

A dying star's final moments are captured in this image from the NASA/ESA Hubble Space Telescope. The death throes of this star may only last mere moments on a cosmological timescale, but this star's demise is still quite ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.