Ruminations: Close Encounters of the Asteroid Kind

"Even though there is no possibility whatsoever of an impact during that encounter, Bennu is going to be fairly close to the Earth."
"Overall the situation has improved. I am not any more concerned about Bennu than I was before; the impact probability remains very small."
"[Although recent findings indicate the odds of impact have increased marginally, from 1-in-2,700 to 1-in-1,750 over the next century, it] does not represent significant change [much less reason for concern]."
Davide Farnocchia, scientist Center for Near Earth Object Studies, NASA

OSIRIS-REx will orbit the sun twice before it is expected to reach Earth in September 2023. Image credits: NASA/Instagram.

Bennu is a rugged, rock-spewing asteroid, its diameter of one-third of a mile substantial enough to raise concerns and it is headed in the direction of our planet with expectations that it will arrive quite close to Earth by September of 2135. NASA scientists however, remain convinced that though Bennu will transit within half the distance of the moon it is highly unlikely that the asteroid might collide with Earth to cause an Armageddon-like destruction.

A study, published in Icarus Journal comes out of the NASA centre, at the Jet Propulsion Laboratory in Southern California which calculates asteroid and comet orbits and the chances of impact occurring. And while researchers believe Earth will not be impacted by the asteroid as it travels close enough to Earth for a mild level of concern, the challenge now is deciphering whether Earth's gravity may alter the asteroid's path around the sun.

The asteroid Bennu, showing the paths followed by the OSIRIS-REx mission during its 2-year close encounter NASA/Goddard/SVS

A small possibility exists that the asteroid might pass through the "gravitational keyhold" and in so doing potentially could place it en route at a later date in the 22nd century when it approaches Earth again. The tiny region in space where a planet's gravity can potentially impact the trajectory of a passing asteroid and place it on a path to a collision is referred to as a gravitational keyhold.

Despite recent findings showing the odds of impact have increased slightly, Dr.Farnocchia emphasizes little cause exists to worry, explaining that a more refined idea of Bennu's path has enlightened scientists wth the use of data collected by NASA's Origins, Spectral Interpretation, Resource Identification Security-Regolith Explorer (OSIRIS-REx) spacecraft which studied the asteroid for more than two years while in orbit.

A depression is visible where Osiris-Rex penetrated the asteroid’s surface. Boulders were hurled by the pressurized nitrogen gas that was fired at the ground to churn up material for vacuuming. Photo: AFP

NASA researchers made use of precision-tracking data for their study from the OSIRIS-REx spacecraft to have a better understanding of Bennu's movements through 2300, raising scientists' capacity to determine the probability of impacting Earth and to predict the orbits of other asteroids. With the use of NASA's Deep Space Network of giant radio antennae supporting interplanetary spacecraft missions and computer models, scientists succeeded in determining Bennu's overall probability of striking is about 1 in 1750 (or 0,057 percent).

In addition to which the day with the highest risk of collision was calculated by the research team, and identified as September 24, 2182. The asteroid recognized for its potential hazardous proximity to Earth as it transits, was originally identified in 1999 by the Lincoln Near-Earth Asteroid Research Team which works on detection and tracking with the use of optical and radar telescopes.

Since its discovery, Bennu has been responsible for three close encounters with Earth; in 1999, 2005 and 2011. Bennu remains one of the two most hazardous (known) asteroids in the solar system; it and another called 1950 DA. The most pressing threat for Earth from space objects are hazardous asteroids that remain as yet undetected, according to the researchers.