<p>Many surface and
dynamical processes affect the evolution of asteroids in our solar
system today. The spectral slopes of S and Q-type asteroids are
altered by the weathering of their surfaces due to solar wind
interactions and micrometeorite impacts, as well as any processes
that work to remove that weathered material. These processes of space
weathering and asteroid resurfacing compete with each other to
determine the spectral slope of each asteroid, with space weathering
raising the spectral slope</p>
<p>and resurfacing
lowering it. By considering the distribution of spectral slopes with
respect to orbital location and size, we can determine which
potential resurfacing processes are the most dominant. I show that
the distribution of spectral slopes with respect to size is present
in all populations of S and Q-type asteroids in the inner solar
system, regardless of orbit. I also show that the spectral slopes of
S and Q-type Near-Earth Asteroids (NEAs) decrease with decreasing
perihelion, but only for perihelia q < 0.9 AU.</p>
<p>By building Monte
Carlo and models N-body simulations of asteroids, I test which
resurfacing mechanisms are consistent with these trends in spectral
slopes. I find that spin-up and failure from the
Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect is an important
resurfacing mechanism that creates the observed weathering trends
with size. I also show that resurfacing asteroids due to close
encounters with the terrestrial planets cannot explain the spectral
slope vs. perihelion trend at q .</p>
<p>0.9 AU, but that
resurfacing asteroids due to thermally induced surface degradation,
by assuming a power law relationship between the resurfacing
timescale and the solar distance, gives much more consistent results.</p>
<p>I also explore the
creation rate of asteroid pairs, which are asteroids that have very
similar orbits but are not gravitationally bound. The majority of
pairs are formed by YORP spin-up and fission, followed by a
separation of the two members. Asteroid pairs are then disassociated
over time as their orbits become less similar due to chaos,
resonances, and the Yarkovsky effect. I simulate both the formation
of asteroid pairs in the inner main belt via YORP and their
subsequent disassociation. By comparing the distribution of orbital
similarity distances from observations and from our model, I estimate
that asteroids fission and create an asteroid pair every 8 − 13
YORP cycles, where a YORP cycle is twice the time it takes the YORP
effect to change the spin rate of an asteroid from zero to its
critical spin rate. I argue that the rate of fissioning via the YORP
effect is not substantially limited by any stagnation or stochastic
evolution, and that losing mass via rotational fission is much less
effective than collisional disruption, even for small asteroids.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7428008 |
| Date | 17 January 2019 |
| Creators | Kevin J. Graves (5929712) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Resurfacing_Asteroids_The_Creation_Rate_of_Asteroid_Pairs/7428008 |
Page generated in 0.0025 seconds