Tuesday, September 22, 2020. 7:00 PM

Villajoyosa University Venue

Adriano Campo Bagatin:
“Asteroid Exploration: Reading the History of the Solar System”

Summary:
220 years after the discovery of the first asteroid, our view of the solar system has profoundly changed. In particular, observations and especially space exploration over the past 30 years have made it possible to study these small bodies in detail, revolutionizing our understanding of how our solar system has evolved.

Link to the Meet session: meet.google.com/txb-rcib-pwm

Event Information:
This event is planned to be in person. For details about seating capacity, please contact the venue:

Villajoyosa University Venue
C/ Colón, 57
03570 Villajoyosa (Alicante)

Tel: (+34) 96 650 8355

Adriano Campo Bagatin, Rafael A. Alemañ, Paula G. Benavidez, Manuel Pérez-Molina, Dereck C. Richardson

Asteroids, the small rocky bodies in our solar system, exhibit a remarkable diversity of shapes. This variety ranges from nearly spherical objects to elongated ones, binary systems (a primary body orbited by a smaller one), and “contact binaries” such as (25143) Itokawa, the target of the Hayabusa mission (JAXA). Contact binaries, in particular, have a distinctive shape characterized by significant mass at their opposite ends, separated by a neck or constriction, resembling a giant peanut. These objects are thought to form through the slow collision of two previously independent bodies that eventually merge into a single entity.

Regardless of their shape, these small bodies spend most of their time within the Asteroid Belt, a region characterized by frequent collisions. Speculations about the origin of the diverse asteroid shapes often involve mechanisms such as collisions (which may group previously separate objects) and the effects of asteroid spin (which could cause parts of the body to break off).

Recent numerical simulations of the gravitational interaction between the components of multi-object systems (n-body systems) have been conducted to analyze the evolution of fragments resulting from catastrophic collisions (Campo Bagatin et al., 2018). This study introduces the idea that the stochastic process of gravitational reaccumulation of these fragments could be responsible for many of the observed asteroid shapes. Shape elongation—both for S-type (silicate-rich) and C-type (carbonaceous) asteroids—shows a tendency to increase with the growth of the initial volume of fragments set to reaccumulate.

Moreover, the conclusions presented in this article suggest that contact binaries could form regularly during the gravitational reaccumulation process following catastrophic impacts. Similar processes may have occurred in some comets and trans-Neptunian objects (those located beyond Neptune’s orbit).

Link to the article

(Internal Structure of Gravitational Aggregates of Asteroids)

Adriano Campo Bagatin, Rafael A. Alemañ, Paula G. Benavidez, Dereck C. Richardson

Most astronomy enthusiasts are familiar with the Asteroid Belt beyond Mars, but it is less well-known that the internal structure of these celestial objects remains largely unexplored due to the lack of direct measurements. Current research in this area relies primarily on theoretical considerations and comparisons between the apparent densities of asteroids and the densities of their meteorite analogs (asteroidal fragments that reach Earth as meteorites).

A significant portion of the bodies within the Asteroid Belt consists of fragment aggregates with a wide variety of sizes and shapes, which contrasts with the popular notion of asteroids as monolithic blocks. The distribution of fragments and voids within a gravitational aggregate (a cluster of fragments held together by their mutual gravitational attraction) determines the structure and properties of these objects.

This study investigates the dynamic evolution of the reaccumulation process of fragments produced by catastrophic collisions (those capable of completely destroying the original asteroid) for asteroids ranging from 500 m to 10 km in size. Numerical simulations using specially designed computational programs were carried out to analyze this process. Special attention was given to the irregular shapes of the aggregate components, utilizing results from laboratory experiments that provide mass distributions and aspect ratios (proportional relationships between the axes of ellipsoids that approximate the irregularity of real shapes) for the fragments.

The findings indicate that the processes determining the final properties of the resulting aggregates—following the reaccumulation of fragments initially dispersed by a catastrophic impact—are primarily stochastic. However, interesting patterns can still be identified. For clarity, the study distinguishes between S-type asteroids (dominated by silicate) and C-type asteroids (dominated by carbon) and differentiates between macroporosity (the proportion of voids between the fragments forming the gravitational aggregate) and microporosity (porosity within the internal structure of each fragment).

The numerical results align with estimated macroporosities of S-type asteroids, revealing an approximately linear relationship between the macroporosity of asteroid aggregates and the mass ratio of the largest fragment to the total aggregate mass (for both S and C types).

Regarding observed C-type asteroids, the study concludes that their interiors are likely more fragmented compared to S-type asteroids, which explains the higher estimated macroporosity in real C-types relative to S-types. Additionally, it was found that slower-spinning asteroids can spontaneously form as a result of gravitational reaccumulation.

This research sheds light on the complex internal structures of asteroids and offers insights into their formation and evolution processes.

Link to the article