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.

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“The Tunguska event just 100 years ago reminds us that the threat of an asteroid strike is real,” said Ray Williamson, Executive Director of the Secure World Foundation (SWF). “If that object had struck in New York City or London, it would have killed hundreds of thousands and created untold fear in human hearts. Yet, as near Earth object strikes go, it was relatively small,” he pointed out.

“We need to be much better prepared than we are today to deal with this important, if uncommon, threat by creating the international institutions and governance methods to find objects likely to strike Earth and devise the means to divert them from Earth’s path,” Williamson explained.

Action agenda

Thwarting the threat of Earth-colliding asteroids – is on the action agenda list for former Apollo astronaut, Russell L. (Rusty) Schweickart.

While a civilization-smashing impact from a space object is a low probability, it is not zero…and there are other trouble-makers out there too. They are the smaller asteroids, in far greater number and could wreak havoc on our world, but in a more localized way.

Speaking recently at a Secure World Foundation luncheon at the University of Colorado – Boulder, Schweickart emphasized that what is needed is an international protocol – “mission rules” — that deal with asteroids that are menacing to Earth. Such a plan could calls upon nations around the globe to consider and embrace steps that can help mitigate the destructive nature stemming from an asteroid striking our planet.

Tree of life

Schweickart’s talk drew from his chairman position of the Association of Space Explorers’ Committee on Near Earth Objects and as Chairman of the B612 Foundation, dedicated to detecting, tracking and deflecting near Earth objects (NEOs).

Coming to grips with the NEO challenge, Schweickart emphasized, is more a matter of humanity’s readiness not to be dinosaurs – thought by many scientists to have been the victims of a huge asteroid impact some 65 million years ago. And that’s why we on Earth, he added, are faced with a key question: “To be…or not to be?”

Indeed, over billions of years, the Tree of Life here on Earth has been whacked time and time again by what Schweickart labeled as “the crazy cosmic gardener.”

“The good news is that we can do something about this,” the former astronaut explained. “The marriage of we human beings and the machines that we’ve created are now at a level of capability which enables us to fire the crazy cosmic gardener. We can stop this process from occurring again.”