Kolizní vývoj hlavního pásu asteroidů po dobu 4 miliard let

• Thesis title in Czech: Kolizní vývoj hlavního pásu asteroidů po dobu 4 miliard let
• Thesis title in English: Collisional evolution of the Main Asteroid Belt over 4 billion years
• Key words: hlavní pás asteroidů; kolize; rozdělení velikostí; asteroidální rodiny
• English key words: Main Asteroid Belt; collisions; size-frequency distribution; asteroid families
• Academic year of topic announcement: 2011/2012
• Thesis type: diploma thesis
• Thesis language: čeština
• Department: Astronomical Institute of Charles University (32-AUUK)
• Supervisor: doc. Mgr. Miroslav Brož, Ph.D.
• Author: hidden - assigned and confirmed by the Study Dept.
• Date of registration: 12.10.2011
• Date of assignment: 13.10.2011
• Confirmed by Study dept. on: 25.10.2011
• Date and time of defence: 20.05.2013 00:00
• Date of electronic submission: 11.04.2013
• Date of submission of printed version: 12.04.2013
• Date of proceeded defence: 20.05.2013
• Opponents: doc. Mgr. Josef Ďurech, Ph.D.

Guidelines

Student zkonstruuje nový kolizní model hlavního pásu planetek,
což sestává z následujících úloh:

- rozdělení planetek hlavního pásu na skupiny podle velké poloosy nebo sklonu;
- konstrukce příslušných pozorovaných rozdělení velikostí
(s využitím nových hodnot albeda odvozených z meření družice WISE);
- určení vzájemných kolizních pravděpodobností;
- výpočet vývoje jednotlivých částí pásu integrátorem 'Boulder';
- prozkoumání parametrického prostoru metodou simplexu,
zejména závislosti na škálovacím zákoně (tj. vztahu rozměr-pevnost);
- diskuze možných iniciálních rozdělení velikostí pásu
a vlivu velkého pozdního bombardování.

References

Bottke W.F., Durda D.D., Nesvorný D., Jedicke R., Morbidelli A., Vokrouhlický D., Levison, H.F. 2005, The fossilized size distribution of the main asteroid belt. Icarus, 175, 111.

Morbidelli A., Bottke W.F., Nesvorný D., Levison H.F. 2009, Asteroid were born big. Icarus, 204, 558.

Preliminary scope of work

TBD

Preliminary scope of work in English

The observed size-frequency distribution of the whole Main Asteroid Belt is a
crucial constraint and there are many collisional models trying to explain its
'wavy' shape ― see for example Bottke et al. (2005) and references therein. In
that particular work, authors constructed a so-called CoDDEM code, which
included also dynamical losses apart from collisional interaction, but they
always regarded the Main Belt as a single population. Moreover, they did not
include cratering events which may eject small fragments and this way decrease
sizes of bodies. These two caveats may be however overcame by using newer
collisional codes.

Morbidelli et al. (2009) studied an early evolution of the Main Belt, motivated
by the paradigm-breaking work of Johansen et al. (2007) who discovered that
turbulence in the gas may create long-lived density fluctuations so that solid
particles gravitationally collapse and create large (up to ~1000 km)
planetesimals. A code nicknamed Boulder was used for the modeling of further
coagulation and fragmentation (this an advanced variant of approaches pioneered
by Weidenschilling, Kenyon & Broomley and others). This code also accounts for
the craterings and enables to use many 'annuli' ― i.e. distinct parts of the
population divided according to their semimajor axes, orbital inclinations,
taxonomy classes, scaling laws, etc.

We believe it is worth to update the previous work of Bottke et al. (2005)
since it is possible we discover substantial differences between the
inner/middle/outer belt or the low-/high- inclination belt in terms of
collisional evolution. Indeed, there are clear differences visible in absolute
magnitude distributions (see Figure 1). We are also motivated by the
inclination-dependent SFD's discovered in the J3/2 resonant population (Brož et
al. 2011) which may be related to different source regions of this population.

Another question is how the Main-Belt background population was created? What
is the dominant process: Yarkovsky-driven dynamical losses from families and
interactions with gravitational resonances, catastrophic or non-catastrophic
disruptions or comminution of asteroid families? Is it possible to explain
larger-than-families structures visible in the Sloan DSS colour data? Are they
somehow related to the LHB?

Recently, young clusters started to be identified in the Main Asteroid Belt ―
either in the space of proper elements (Nesvorný et al. 2002) or of osculating
elements (Nesvorný & Vokrouhlický 2006). This will definitely continue in the
future as new surveys (PanSTARRS, LSST) acquire astrometric and photometric
data for many sub-kilometer bodies.

On the other hand, ancient structures in the Main Belt are poorly known. One of
the reasons is that the methods (like the hierarchical clustering, HCM) is
optimized for young and compact families while the old dispersed/comminutioned
clusters may look like very differently. A systematic search of such old
structures (in case we know what to look for) may be possible in the Sloan DSS
colour data. A promising part of the Main Belt is the region between the J2/1
and J7/3 resonances (from 2.83 to 2.95 AU) where only a single large family
disrupted in the past (the Koronis family), the region is relatively empty and
thus old structures may be easily visible.