The flux of meteorites and near-Earth objects (NEOs) in the past

In addition to understanding the mechanisms of material transport from the main belt, which are primarily gravitational resonances (Wisdom 1983, Icarus 56, 51) and the Yarkovsky effect (Farinella & Vokrouhlický 1999, Science 283, 1507), it is important to quantitatively describe the flux of meteorites and near-Earth objects (NEOs) in the past. Our collisional and orbital simulations (Marsset et al. 2024, Nature 634, 561; Brož et al. 2024, Nature 634, 566; Brož et al. 2024, A&A 689, A183) are time-dependent and therefore make it possible to study past events and their impact on the Earth-Moon system. In collaboration with A. Lagain, we have so far interpreted lunar cratering over the past 3.2 billion years (Lagain et al., Nature, submitted), but it is also necessary to study cratering in the same way on other bodies (Mars, Mercury, Vesta, . . . ). In the case of Mars, there is potential to understand, or even precisely date, the formation of major geological units such as Tharsis Planitia and Vastitas Borealis.

Lunar cratering (Ivanov et al. 2001, Space Sci. Rev. 96, 87) represents a detailed and fairly complete record of past events for the Earth-Moon system, since cratering on Earth (Kenkmann & Artemieva 2021, Meteorit. Planet. Sci. 56, 1024) is incomplete. Thanks to the development of neural networks (Fairweather et al. 2023, Earth Planet. Sci. 10, e2023EA002865) and high-resolution imaging of the Moon by the Kaguya spacecraft (Haruyama et al. 2008, Earth Planet. Sci. 60, 243), it is now possible to determine the ages of individual, large (>20 km) craters based on the number of small (∼100 m) craters on their rims; their accumulation is proportional to age. However, the challenge lies in distinguishing the flux of large vs. small projectiles, which may or may not be correlated. We have addressed precisely this issue by using models for 56 asteroid families (Brož et al. 2024, A&A 689, A183), which describe the entire size distribution as well as its temporal evolution.

To address the problem of cratering on Mars, a multidisciplinary approach is required, which includes: expanding the list of asteroid family models (Nesvorný et al. 2024, AJSS 274, 25), for new families, simulating their orbital evolution (Brož et al. 2011, MNRAS 414, 2716), simulating their collisional evolution (Morbidelli et al. 2009, Icarus 204, 558), determining their ages, determining the collision probability with Mars, calculating the cumulative number of craters as a function of time, comparing with observed crater counts, determining the ages of major geological units. A related task may be the use of convolutional neural networks (YOLOv12; Redmon et al. 2015, arXiv 1506.02640) for counting craters themselves, which are too numerous (10⁷) to be counted manually. For Mars, a suitable dataset is, for example, images from the Mars Reconnaissance Orbiter with a resolution of ∼5 m/px (MRO CTX; Lagain et al. 2021, Nat. Commun. 12, 6352).

A student should have knowledge of the Linux operating system, programming in Fortran or C, programming in Python, the ability to study related subfields (celestial mechanics, meteorite chemistry), analytical skills, the ability to work independently as well as collaboratively with international experts (A. Lagain, P. Vernazza, D. Nesvorný).

https://sirrah.troja.mff.cuni.cz/~mira/tmp/PhD_kraterovani/README_cz.pdf

References:

Lagain et al., Nature, submit.
Marsset et al. 2024, Nature 634, 561.
Brož et al. 2024, Nature 634, 566.
Brož et al. 2024, A&A 689, A183.
Brož et al. 2011, MNRAS 414, 2716.
Fairweather et al. 2023, Earth Planet. Sci. 10, e2023EA002865.
Farinella & Vokrouhlický 1999, Science 283, 1507.
Haruyama et al. 2008, Earth. Planet. Sci 60, 243.
Ivanov et al. 2001, Space Sci. Rev. 96, 87.
Kenkmann & Artemieva 2021, Meteor. Planet. Sci. 56, 1024.
Lagain et al. 2021, Nat. Comm. 12, 6352.
Morbidelli et al. 2009, Icarus 204, 558.
Nesvorný et al. 2024, AJSS 274, 25.
Redmon et al. 2015, Arxiv 1506.02640.
Wisdom 1983, Icarus 56, 51.