Recent NASA missions to asteroids have gathered important data about the early evolution of our Solar System, planet formation, and how life may have originated on Earth. These missions also provide crucial information about how to deflect asteroids that could hit Earth.
Missions like the OSIRIS-REx mission to asteroid Bennu and Japan鈥檚 Hayabusa 2 mission to asteroid Ryugu are often conducted by robotic explorers that send images back to Earth showing complex asteroid surfaces with cracked, perched boulders and rubble fields.
In order to better understand the behavior of asteroid material and design successful robotic explorers, researchers must first understand exactly how these explorers impact the surface of asteroids during their touchdown.
Researchers from the 人妻少妇专区鈥檚 , including , a professor of physics and astronomy, and Esteban Wright, a graduate student in Quillen鈥檚 lab, conducted lab experiments before the quarantine lockdown in March to determine what happens when explorers and other objects touch down on complex, granular surfaces in low-gravity environments. Their research, published in the , provides important information in improving the accuracy of data collection on asteroids.
鈥淐ontrolling the robotic explorer is paramount to mission success,鈥� Wright says. 鈥淲e want to avoid a situation where the lander is stuck in its own landing site or potentially bounces off the surface and goes in an unintended direction. It may also be desirable for the explorer to skip across the surface to travel long distances.鈥�
The researchers used sand to represent an asteroid鈥檚 surface in the lab. They then used marbles to measure how objects impact the sandy surfaces at different angles, and filmed the marbles with high-speed video in order to track the marbles鈥� trajectories and spin during impact with the sand.
鈥淕ranular materials like sand are usually quite absorbent upon impact,鈥� Quillen says. 鈥淪imilar to a cannonball ricocheting off of water, pushed sand can act like a snow in front of a snowplow, lifting the projectile, causing it to skip off the surface.鈥�
Collaborating with members of Rochester鈥檚 Departments of , , and , the researchers constructed a mathematical model that includes the Froude number, a dimensionless ratio that depends on gravity, speed, and size. By scaling the model with the Froude number, the researchers were able to apply the knowledge gained from their experiments with the marbles to low-gravity environments, such as those found on asteroid surfaces.
鈥淲e found that at velocities near the escape velocity鈥攖he velocity at which an object will escape gravitational attraction鈥攎any if not most rocks and boulders are likely to ricochet on asteroids,鈥� Wright says.
The results provide an explanation for why asteroids have strewn boulders and rocks that are perched on their surfaces, and they also influence the angle at which robotic missions will need to successfully touch down on the surface of an asteroid.
鈥淩obotic missions that touch down on the surface of an asteroid will need to control the moment of touch down so that they don’t bounce,鈥� Quillen says. 鈥淭he robots can accomplish this by making their angle of impact nearly vertical, by reducing the velocity of impact to a very small value, or by making the velocity of impact large enough to form a deep crater that the robotic explorer won鈥檛 bounce out of.鈥�
Grants from NASA and the National Science Foundation supported this research.
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