A NASA scientist has revealed that the agency has no idea about the behavior of at least 20,000 asteroids. These asteroids could suddenly end up on a collision course with Earth due to a cosmic phenomenon known as the Yarkovsky effect.

Currently, NASA has various systems in place to identify asteroids orbiting within Earth’s neighborhood. The main objective of these systems is to monitor asteroids that could collide with the planet in the future.

However, according to asteroid expert Steve Chesley of NASA’s Jet Propulsion Laboratory, the trajectories of newly-discovered asteroids are a bit hard to predict due to the lack of necessary data. This, of course, poses a problem when it comes to identifying asteroids with non-zero Earth impact probabilities.

“When an asteroid is first discovered, we really don’t know even which way the asteroid is being pushed. It could be pushed ahead or behind its orbit,” he said, according to Express. “That can be a very complicating effect on the Earth hazard prediction for many asteroids.”

According to Chesley, one of the main factors that contribute to the unpredictable nature of asteroids is a cosmic phenomenon known as the Yarkovsky effect. This occurs when sunlight hits an asteroid and heats up its surface. After the asteroid absorbs the heat, it emits it in the form of heat radiation.

The heat radiation escaping from the space rock’s surface acts like a thruster system that causes the asteroid to spin and move towards a new direction. Chesley noted that due to the Yarkovsky effect, NASA is having a hard time accurately predicting the trajectories of asteroids. Currently, Chelsey revealed that there are about 20,000 asteroids that could be affected by this cosmic phenomenon.

“Now we have on the order of 100 near-Earth asteroids for which we can see and estimate the amount of Yarkovsky effect but there are still 20,000 more near-Earth asteroids for which we have no insight of what the Yarkovsky effect is doing to that body,” the scientist explained.

Through the Yarkovsky effect, these thousands of asteroids could get nudged into a trajectory that could take them straight to Earth.

NASA Asteroid family Mars and Jupiter
This artist concept catastrophic collisions between asteroids located in the belt between Mars and Jupiter and how they have formed families of objects on similar orbits around the sun. NASA/JPL-Caltech
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