New Candidates for Recent Asteroid Breakups

Abstract

Asteroids in our solar system formed in a dynamically quiescent disk, but their orbits became gravitationally stirred enough by Jupiter to lead to high-speed collisions. As a result, several dozen large asteroids have been disrupted by impacts over the past several gigayears and have produced groups of fragments called asteroid families. Here we report three new candidates for asteroid families that were formed by collisions occurring in the last 1 Myr. According to our modeling of the past orbital histories of known cluster members, we estimate that the Emilkowalski, 1992 YC2, and Lucascavin clusters are 220 AE 30, 50 Y250, and 300Y800 kyr old, respectively. Together with the previously identified Datura cluster, estimated to be 450 AE 50 kyr old, they are the most recent asteroid breakups ever discovered in the main belt. Astronomical observations of identified family members can be used to better understand impact physics, asteroid composition, and surface-aging processes. Discovered breakups may also be important sources of interplanetary dust.

Identifying Collisional Families in the Kuiper Belt

“…Rather, very tight young asteroid families are identified and then back integrated (either with or without the Yarkovsky effect) to confirm that the objects were tightly clustered in their past and to obtain an age estimate (Nesvorný et al 2002;Nesvorný & Vokrouhlický 2006). This technique works best when the objects are on orbits that are rather stable, e.g., Lyupanov timescales that are not much shorter than the duration of the integration (Nesvorný & Vokrouhlický 2006) and can give very accurate ages.…”

“…Rather, very tight young asteroid families are identified and then back integrated (either with or without the Yarkovsky effect) to confirm that the objects were tightly clustered in their past and to obtain an age estimate (Nesvorný et al 2002;Nesvorný & Vokrouhlický 2006). This technique works best when the objects are on orbits that are rather stable, e.g., Lyupanov timescales that are not much shorter than the duration of the integration (Nesvorný & Vokrouhlický 2006) and can give very accurate ages. 2 Backward integration could be used in the asteroid belt for finding families and could even potentially include the effect of Yarkovsky (e.g., following Nesvorný & Vokrouhlický 2006) with the main drawback being the computational limitation in integrating dozens of clones of the hundreds of thousands of known asteroids over potentially long times.…”

“…This technique works best when the objects are on orbits that are rather stable, e.g., Lyupanov timescales that are not much shorter than the duration of the integration (Nesvorný & Vokrouhlický 2006) and can give very accurate ages. 2 Backward integration could be used in the asteroid belt for finding families and could even potentially include the effect of Yarkovsky (e.g., following Nesvorný & Vokrouhlický 2006) with the main drawback being the computational limitation in integrating dozens of clones of the hundreds of thousands of known asteroids over potentially long times. This drawback has led to the more practical and presumably equally effective technique of searching for tight clusters in proper elements.…”

“…Thus, many of the difficulties with finding families using proper elements alone in the current Kuiper Belt are avoided. The statistical strength of these clusters can be compared with random clusterings that occur during most of the history of the solar system, which should allow for rigorous identification of families as more than random clumpings, which are generally very rare even for small numbers of objects (Nesvorný & Vokrouhlický 2006). An additional advantage is gained by the much slower evolution of orbits in the Kuiper Belt as compared to the asteroid belt; scaling from known asteroid families, this suggests clusters older than ∼100 Myr could be found.…”

Re-assessing the ordinary chondrites paradox

“…In this taxonomic scheme, an asteroid belongs to a given taxonomic class according to the presence or absence of specific features in its visible spectrum, from 0.44 to 0.92 µm and to values of particular parameterized spectral characteristics. The taxonomic class attributed to each object is shown in Table 2, where we also list five small main-belt objects observed by Mothé-Diniz & Nesvorný (2008a), which according to Nesvorný & Vokrouhlický (2006) belong to very young families (ages <500 kyr). Some of the objects had characteristics that were intermediate between two classes of Bus.…”