Washington, January 21 (ANI): In a new research, scientists have determined that asteroids that come relatively close to Earth can experience a strong "seismic shake".
The research was carried out by MIT (Massachusetts Institute of Technology) Professor of Planetary Science Richard Binzel.
Binzel analyzed telescopic measurements of near-Earth asteroids (NEAs), or asteroids that come within 30 million miles of Earth.
Binzel's team used a large NASA telescope in Hawaii to collect information on NEAs, including a huge amount of spectral fingerprint data.
Analyzing this data, the group examined where a sample of 95 NEAs had been during the past 500,000 years, tracing their orbits to see how close they'd come to Earth.
They discovered that 75 NEAs in the sample had passed well inside the moon's distance within the past 500,000 years, including all 20 fresh asteroids in the sample.
Binzel 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.
The research 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, according to Binzel.
Many details about the shaking process remain unknown, including what exactly it is about Earth that shakes the asteroids, and why this happens from a distance as far away as 16 Earth radii.
What is certain is that the conditions depend on complex factors such as the velocity and duration of the encounter, the asteroid's shape and the nature of the preexisting regolith. (ANI)