Hungaria asteroids, whose orbits occupy the region in element space between 1.78 < a < 2.03 AU, e < 0.19, 12 • < i < 31 • , are a possible source of Near-Earth Asteroids (NEAs). Named after (434) Hungaria these asteroids are relatively small, since the largest member of the group has a diameter of just about 11 km. They are mainly perturbed by Jupiter and Mars, possibly becoming Marscrossers and, later, they may even cross the orbits of Earth and Venus. In this paper we analyze the close encounters and possible impacts of escaped Hungarias with the terrestrial planets. Out of about 8000 known Hungarias we selected 200 objects which are on the edge of the group. We integrated their orbits over 100 million years in a simplified model of the planetary system (Mars to Saturn) subject only to gravitational forces. We picked out a sample of 11 objects (each with 50 clones) with large variations in semi-major axis and restarted the numerical integration in a gravitational model including the planets from Venus to Saturn.Due to close encounters, some of them achieve high inclinations and eccentricities which, in turn, lead to relatively high velocity impacts on Venus, Earth, and Mars. We statistically analyze all close encounters and impacts with the terrestrial planets and determine the encounter and impact velocities of these fictitious
Centaurs are objects whose orbits are found between those of the giant planets. They are supposed to originate mainly from the Trans-Neptunian objects, and they are among the sources of Near-Earth Objects. Trans-Neptunian Objects (TNOs) cross Neptune's orbit and produce the Centaurs. We investigate their interactions with main belt asteroids to determine if chaotic scattering caused by close encounters and impacts by these bodies may have played a role in the dynamical evolution of the main belt. We find that Centaurs and TNOs that reach the inner Solar System can modify the orbits of main belt asteroids, though only if their mass is of the order of 10 −9 m ⊙ for single encounters or, one order less in case of multiple close encounters. Centaurs and TNOs are unlikely to have significantly dispersed young asteroid families in the main belt, but they can have perturbed some old asteroid families. Current main belt asteroids that originated as Centaurs or Trans-Neptunian Objects may lie in the outer belt with short lifetime ≤ 4M y, most likely between 2.8 au and 3.2 au at larger eccentricities than typical of main belt asteroids.
The Hungaria Family (the closest region of the Main Belt to Mars) is an important source of Planet-Crossing-Asteroids and even impactors of terrestrial planets. We present the possibility that asteroids coming from the Hungaria Family get captured into co-orbital motion with the terrestrial planets in the inner solar system. Therefore we carried out long term numerical integrations (up to 100 Myr) to analyze the migrations from their original location -the Hungaria family region-into the inner solar system. During the integration time we observed whether or not the Hungarias get captured into a co-orbital motion with by the terrestrial planets. Our results show that 5.5 % of 200 Hungarias, selected as a sample of the whole group, escape from the Hungaria region and the probability from that to become co-orbital objects (Trojans, satellites or horseshoes) turns out to be ∼ 3.3%: 1.8% for Mars and 1.5% for the Earth. In addition we distinguished in which classes of co-orbital motion the asteroids get captured and for how long they stay there in stable motion. Most of the escaped Hungarias become Quasi-satellites and the ones captured as Trojans favour the L 5 lagrangian point. This work highlights that the Hungaria region is a source of Mars and also Earth co-orbital objects.
Context. Most howardite-eucrite-diogenite (HED) meteorites (analogues to V-type asteroids) are thought to originate from the asteroid (4) Vesta. However some HEDs show distinct oxygen isotope ratios and therefore are thought to originate from other asteroids. In this study we try to identify asteroids that may represent parent bodies of those mismatching HEDs. Aims. The main goal of this study is to test the hypothesis that there might be V-type asteroids in the inner main asteroid belt unrelated to (4) Vesta. In order to evolve outside the Vesta family and became Vesta fugitives, asteroids should produce the correct Yarkovsky drift. The direction of which is dependent on asteroid sense of rotation. Therefore we focus on determining sense of rotation for asteroids outside the Vesta family to better understand their origin. Methods. We performed photometric observations using the 1.1 m and 1.8 m telescopes at Lowell Observatory to determine rotational synodic periods of selected objects before, at, and after opposition. Prograde rotators show a minimum in synodic period at opposition while retrograde rotators show a maximum. This is known as the "drifting minima" method. Changes in the rotational period are on the order of seconds and fractions of seconds and depend on the rotational pole of the object and the asteroid-observer-Sun geometry at opposition. Results. We have determined sense of rotation for eight asteroids and retrieved spin states for three objects from literature. For one asteroid we were not able to determine the sense of rotation. In total our sample includes 11 V-type asteroids and one S-type (test object). We have revised rotation periods for three objects. Five V-types in our sample can be explained by migration from the Vesta family. Two show spin states that are inconsistent with migration from Vesta. The origin of the remaining objects is ambiguous. Conclusions. We found two objects with rotations inconsistent with migration from Vesta. Assuming that the YORP effect and random collisions did not substantially modify their sense of rotation, those objects are candidates for non-Vestoids in the inner asteroid belt. Finding more non-Vestoids is crucial in testing the formation and migration theory of differentiated parent bodies.
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