[ METEOMOD | NEOMOD | Documentation ]
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A new orbital distribution model for meteoroids ('METEOMOD')
is used to estimate a probability of coming from a source.
Hereinafter, we assume that the source is one of asteroid families,
located between 1.9 and 3.5 au,
from where meteoroids are transported towards the Earth.
To estimate the importance of each source,
a-priori knowledge of its size-frequency distribution (SFD)
is critical, since young asteroid families tend to have a steep SFD
down to metre-sized bodies
(Marsset et al. submit.,
Brož et al. submit.).
The METEOMOD currently contains 52 families. It is based on simulations of transport described in ref. Brož et al. (submit.). Each family is represented by at least 103 particles. These simulations included perturbations by 11 massive bodies (Sun, Mercury to Neptune, Ceres, Vesta), gravitational resonances, the Yarkovsky effect, the YORP effect, collisional reorientations, or cohesive-strength spin barrier, which altogether determine the non-gravitational acceleration (Brož et al. 2011). For simplicity, all particles had sizes 1 m. Their densities and thermal parameters were chosen according to meteorite analogues (i.e., H chondrites for H-chondrite-like families, etc.). |
We computed maps
Mj
of probability distribution in the NEO space,
when eccentricities are already high,
e > 1 − 1.3 au/a,
and the original values of e were lost.
For each source j and for all time steps
(103 y),
we counted orbits located in bins
of the semimajor axis a versus inclination i;
the binning was 0.01 au and 1°, respectively.
These are the most important elements,
which allowed us to recognize the source region of
L chondrites (Marsset et al. submit.) and
H chondrites (Brož et al. submit.).
One should focus on the most distant orbits,
with the lowest values of i,
which are still located close to the source.
The actual numbers of bodies Nneo(>1 m) for each source were also taken from ref. Brož et al. (submit.). Based on collisional modelling, the observed SFDs were extrapolated from kilometre- to metre-sized bodies. The relation between main-belt and NEO populations is determined by the transport, Nneo(>1 m) = τneo/τmb Nmb(>1 m), where τneo denotes the mean lifetime in NEO and τmb, the decay time in the main belt. Since we study meteoroids colliding with the Earth, the maps should be weigthed by the flux Φ = pcoll Nneo(>1 m), where pcoll denotes the mean collisional probability with the Earth (in km−2 y−1 units). The probability of coming from a source is then estimated as pj = Mj(a, i) Φ, with an overall normalisation by Σj pj. |
Our approach is markedly different from refs. Bottke et al. (2002), Granvik et al. (2016), Granvik & Brown (2018), Nesvorný et al. (2023), where sources correspond to resonances (ν6, 3:1, 5:2, 2:1, ...). This is a disadvantage though, because information about the original elements (a, e, i) was largely lost. Moreover, here we use SFDs of the sources, which serve as weights. Last but not least, here we use taxonomy of the sources, which prevents ambiguities. |
| Adeona (CM) | Aeolia (CO/CV/CK) | Aeria (M) | Agnia (H) | Alauda (CI) |
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| Astrid (CM) | Baptistina (CR) | Beagle (CI) | Brängane (M) | Brasilia (M) |
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| Brucato (?) | Chloris (CM) | Clarissa (CI) | Dora (CM) | Elfriede (CI) |
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| Emma (IDP) | Eos (CO/CV/CK) | Erigone (CM) | Eunomia (LL) | Euphrosyne (CI) |
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| Flora (LL) | Gefion (L) | Hoffmeister (CI) | Hungaria (E) | Hygiea (CI) |
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| Iannini (?) | Juno (L) | Kalliope (M) | Karin (H) | König (?) |
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| Koronis (H) | Lixiaohua (CI) | Maria (H) | Massalia (L) | Merxia (H) |
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| Misa (CI) | Naema (CI) | Nemesis (CI) | Nysa (LL) | Padua (IDP) |
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| Pallas (B) | Phocaea (H) | Polana (CI) | Sylvia (P) | Themis (CI) |
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| Theobalda (CM) | Ursula (CI) | Veritas (CM) | Vesta (HED) | Vibilia (CM) |
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| Watsonia (CO/CV/CK) | Phaethon (CY?) | |||
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Miroslav Brož (miroslav.broz@email.cz), Nov 28th 2023