NEOs: impactors, origins and stable orbits

This project will deal with asteroids, airless rocky bodies ranging from 1000 km to 10 m in size and smaller, and comets, active asteroids which usually produce tails of dust and gas. These `minor bodies` are the left-over ingredients of the formation of our planets, which were born from the violent accumulation of asteroids and comets over 4 billion years ago. This project aims to answer the question What role did the minor bodies play in the evolution of the planets and satellites of our Solar System in its recent history (about the last billion years)? The avenue of approach is centered on better understanding the current properties of the small bodies of the Solar System: asteroids, comets and their fragments, meteoroids. More specifically, we will focus on near-Earth objects (NEOs). NEOs have (for the most part) escaped from the main asteroid belt and so present a more easily studied subsample of these asteroids owing to their closer proximity to Earth and the terrestrial planets. Much has been learned about the main belt in that way. This research is subdivided in three main sections: 1. Impacts of asteroids with terrestrial planets and origins of the impactors (Dynamical studies and observational studies), 2. Delivery of meteorites against the Earth from Mars and its moonlets, and from Jovian satellites and 3. Possible Trojans and Moonlets of the Solar System and as possible terrestrial planets-colliders. The first section considers recent impacts on terrestrial planets and the evolution of the asteroids from different region of the Solar system which might become potential hazardous asteroids (PHAs) for the terrestrial planets and making also short studies on the dimensions of the possible resulting craters and the energy released. To analyze possible impactors, photometry and observations will be performed on asteroids via photometry in different bands, gaining informations useful for the non-gravitational forces (such as the Yarkovsky and YORP (YarkovskyO`KeefeRadzievskiiPaddack) effects, which can influence the orbit of small asteroids. The second section will study the arrival of meteors on the Earth, also observing them via devices like CAMO (the Canadian Automated Meteor Observatory) at the CPSX (Centre for Planetary Science and Exploration). In particular, we will examine the connection of these meteors with Mars, the Moon and planets, and the Jovian satellites, too, which may be capable of releasing material to Earth. The last part suggested in the proposal will deal with co-orbital bodies, both those that are unstable in their orbits (possible future PHAs), as well as those that are stable on very long time scales and which may provide information on the conditions that existed when the planets that they accompany were being born.

This project aimed to study the Near-Earth Objects, comets and asteroids which have orbits capable to pass through the terrestrial planets region and have close encounters and even impacts with them. Thus the main interest was to find where these objects, who are potentially impactors of planets like the Earth, Mars and Venus, come from and how they arrive here. Their orbits were studied in details and as subtopics also their type of orbits were studied, e.g. some of them can become co-orbital objects and become quasi-moons of the planets or Trojans or horseshoes, meaning that some asteroids (of former comets) may share similar orbits with some terrestrial planets. Then as another subtopic also the physical characteristics of some of these objects were studied via photometric observations and in case of impact, it was also computed which crater they might produce (in term of size).Concerning impacts it was found that basaltic asteroids (called V-types), asteroids which mainly were components of asteroid Vesta (the second biggest asteroid of the main belt, about a million of asteroids orbiting between Mars and Jupiter), can collide with terrestrial planets and make catastrophic events, because they can produce craters large until 33 km in diameter on the Earth (and up to 75 km on Mars) and collide with our planet every ~12 My (at least for the present know population of V-type asteroids). Then studying the Centaurs, asteroids and comets between Jupiter and Neptune, can arrive in the inner solar system and create instabilities in the main belt ejecting out some of their members after close approaches. This is done especially by large Centaurs which has a mass larger than Ceres, and it was found that this can happen since 3.8 Gyr ago, but even before and in the recent era (last ~2 billion years), it can happen but it is pretty unusual. From this work Dr. Galiazzo showed the preliminary results in several conferences about the impact probabilities of the Centaurs, a consequence of this aforementioned work, because after the first paper where he noticed that Centaurs have multiple close encounters with terrestrial planets, he saw that we can also have collisions from them (this paper is next to be submitted right after the end of this project in another scientific paper).Then physical properties of some regions of the solar system were potential impactors might come from were studied, investigating the color indices of the asteroids and the comets (in particular comet ISON, which had a close encounter with Mars, in particular). The color indices can give an idea of the surface of these objects. In particular via the FIGL observatories many observations were performed, but also with other telescopes thanks to personal collaborations of Dr. Galiazzo, i.e. telescopes in Chile and in China.In particular there were observed some V-type asteroids, the Tina family (a group of asteroid in the main belt), some Centaurs and 2 Trans-Neptunian Objects (bodies after Neptune) and many other asteroids in different region of the main belt. This is important to know potential material which might arrive to the terrestrial planets and in particular to the Earth in the form of meteors and/or meteorites. An important study was also performed on the material ejected out after impacts from the Martian moons (Phobos and Deimos), which have a peculiar surface material and it was shown that this material can arrive to the Earth, thus some meteorites of the Earth might come from Phobos and Deimos. A bit out of topic, it was also studied the origin of Comet 67P/Churyumov-Gerasimenko, the first comet were a space probe landed and a press-release was also given about.This knowledge was shared also with Austrian students, especially giving lectures on the topic at the Department of Astrophysics of the University of Vienna and giving several public talks, nevertheless Dr. Galiazzo was also the organizer of the Asteroidday at that department.Finally some works of this project has to be finalized and can be source of further studies, because this is a topic still studied in several universities and center of research (even private) around the globe. All these works are and can be inspiration for further works and projects, as far as, also, many citations are showing this.