Near-Earth Encounters Can 'Shake' Asteroids
For decades, astronomers have analyzed the impact that asteroids could have on Earth.
New research by MIT Professor of Planetary Science Richard Binzel examines the opposite scenario: that Earth has considerable influence on asteroids - and from a distance much larger than previously thought.
The finding helps answer an elusive, decades-long question about where most meteorites come from before they fall to Earth and also opens the door to a new field study of asteroid seismology.
By analyzing telescopic measurements of near-Earth asteroids (NEAs), or asteroids that come within 30 million miles of Earth, Binzel has determined that if an NEA travels within a certain range of Earth, roughly one-quarter of the distance between Earth and the moon, it can experience a "seismic shake" strong enough to bring fresh material called "regolith" to its surface.
These rarely seen "fresh asteroids" have long interested astronomers because their spectral fingerprints, or how they reflect different wavelengths of light, match 80 percent of all meteorites that fall to Earth, according to a paper by Binzel appearing in the Jan. 21 issue of Nature. The paper suggests that Earth's gravitational pull and tidal forces create these seismic tremors.
By hypothesizing about the cause of the fresh surfaces of some NEAs, Binzel and his colleagues have tried to solve a decades-long conundrum about why these fresh asteroids are not seen in the main asteroid belt, which is between Mars and Jupiter.
They believe this is because the fresh surfaces are the result of a close encounter with Earth, which obviously wouldn't be the case with an object in the main asteroid belt. Only those few objects that have ventured recently inside the moon's orbital distance and have experienced a "fresh shake" match freshly fallen meteorites measured in the laboratory, Binzel said.
Clark Chapman, a planetary scientist at the Southwest Research Institute in Colorado, believes Binzel's work is part of a "revolution in asteroid science" over the past five years that considers the possibility that something other than collisions can affect asteroid surfaces.
"Asteroids. For decades, astronomers have analyzed the impact that asteroids could have on Earth. New research by MIT Professor of Planetary Science Richard Binzel examines the opposite scenario: that Earth has considerable influence on asteroids -- and from a distance much larger than previously thought. (Credit: NASA)"
Source: Massachusetts Institute of Technology
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