Unraveling the Diamond Shape of Asteroids: A Simple Physics Approach
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Understanding the Nature of Asteroids
In our ongoing exploration of the cosmos, particularly our solar system, we often revisit familiar concepts. We've previously discussed various asteroids and the challenges in capturing their images, especially those that are near Earth. This concern drives us to launch missions aimed at uncovering their composition and histories. The data we collect not only enhances our understanding of the solar system's past but also helps us assess the potential risks these celestial bodies pose to our planet.
Our focus now shifts to two intriguing asteroids—Bennu and Ryugu. Bennu was the target of the OSIRIS-REx mission, which involved a dedicated team from CosmoQuest mapping thousands of images and analyzing millions of rocks and boulders to identify a safe sampling site. The collected sample is expected to return to Earth in 2023. Meanwhile, Ryugu was explored by JAXA’s Hayabusa2 spacecraft, which successfully returned samples that are currently under scientific examination.
The Remarkable Shapes of Bennu and Ryugu
Both asteroids share more than just sampling missions; they are also characterized by their diamond shapes and are classified as rubble pile asteroids. Composed of loose fragments of rock and dust, they have managed to coalesce with minimal compression and gravitational influence. OSIRIS-REx principal investigator Dante Lauretta likened Bennu to a “ball pit.” Surprisingly, the samples retrieved from these asteroids were larger than anticipated, with OSIRIS-REx's sampling arm penetrating nearly half a meter into Bennu.
But what accounts for their unique diamond configurations? This question has intrigued planetary scientists, especially given that these asteroids lack the gravitational force necessary to form a spherical shape. Fortunately, a collaborative study by researchers at the Okinawa Institute of Science and Technology (OIST) and Rutgers University offers new insights, attributing the diamond shapes to fundamental physics principles.
The previous theory suggested that asteroid rotation pushed material towards the poles, yet simulations often resulted in flattened, asymmetrical shapes. Lead author Dr. Tapan Sabuwala indicated that earlier models overlooked a crucial factor: the deposition of material. By applying a straightforward granular physics model, typically employed in studying the behavior of grains like sand or sugar, researchers successfully replicated the observed shapes.
To illustrate, consider the act of pouring sand through a funnel; various forces will naturally form a conical pile, reminiscent of a party hat. When combined with the asteroids' gravitational orientation and rotation, this process yields a diamond shape. Essentially, the centrifugal force generated by rotation facilitates the accumulation of rock and dust at the poles, leading to the distinctive shapes observed. Additionally, these asteroids likely acquired their diamond forms early in their existence, as they do not exhibit deformations typical of larger spheres.
Embracing the Basics of Science
Sometimes, returning to fundamental principles and re-evaluating established theories can lead to valuable discoveries. This fresh perspective makes Bennu all the more fascinating for its unique characteristics from the very beginning.
The first video titled "How Science Harnesses The Incredible Power Of Diamonds" delves into the intriguing applications of diamond properties in scientific advancements.
The second video, "Finding Asteroids Before They Strike - Astronomy on Tap - 1/24/2022," discusses the importance of identifying and tracking asteroids that could pose threats to Earth.