Research led by Curtin University on the durability and age of an ancient asteroid made of rocky rubble and dust has yielded significant findings that could aid in protecting Earth from potential asteroid impacts. The international team analyzed three dust particles from the surface of the 500-meter-long asteroid Itokawa, which was brought back to Earth by the Hayabusa 1 probe of the Japanese Space Agency. The study found that Itokawa, located 2 million kilometers from Earth and around the size of Sydney Harbour Bridge, is difficult to break apart and resistant to collisions.
According to lead author Professor Fred Jourdan, Director of the Western Australian Argon Isotope Facility, the study also revealed that Itokawa is nearly as old as the solar system itself. “Itokawa belongs to the rubble pile family, which means it’s composed of loose boulders and rocks, with nearly half of it being empty space,” Professor Jourdan said. “The estimated lifespan of monolithic asteroids the size of Itokawa in the asteroid belt is only several hundred thousand years.”
According to lead author Professor Fred Jourdan, the research revealed that the asteroid Itokawa is like a giant space cushion, hard to destroy and can survive an astonishingly long time. The research team found that the considerable impact that created Itokawa, from the destruction of its monolithic parent asteroid, happened at least 4.2 billion years ago. “This long survival time is due to the shock-absorbent nature of rubble pile material,” said Professor Jourdan.
The research team used two complementary techniques to analyze the three dust particles; Electron Backscattered Diffraction, which measures if a rock has been shocked by any meteor impact and argon-argon dating, which is used to date asteroid impacts. Co-author Associate Professor Nick Timms from Curtin’s School of Earth and Planetary Sciences added that the durability of rubble pile asteroids was previously unknown, which jeopardized the ability to design defence strategies in case one was headed towards Earth.
“Our goal was to determine if rubble pile asteroids are resilient to impact or if they break apart easily,” said Associate Professor Nick Timms. “Our findings indicate that they can survive in the solar system for almost its entire history, meaning they are likely more abundant in the asteroid belt than previously believed. This increases the likelihood that if a large asteroid were to collide with Earth, it would be a rubble pile.”
“The positive aspect of this research is that it can be utilized to our advantage,” said Professor Fred Jourdan. “If an asteroid is identified too late for a kinetic deflection, we can potentially use a more forceful method, such as redirecting a rubble pile asteroid with a nearby nuclear explosion, without destroying it.” The research team at Curtin University includes Associate Professor William Rickard, Celia Mayers, Professor Steven Reddy, Dr David Saxey and John Curtin Distinguished Professor Phil Bland, all from the School of Earth and Planetary Sciences.
Published in the Proceedings of the National Academy of Sciences, the research titled “Rubble Pile Asteroids are Forever” is available online here
