Circumstellar discs are known to exist in great variety, from gas-rich discs around the youngest stars to evolved debris discs such as the solar system’s zodiacal cloud. Through gravitational interaction, exoplanets embedded in these discs can generate density variations, imposing potentially observable structural features on the disc such as rings or gaps. Here we report on a mirrored double crescent pattern arising in simulations of discs harbouring a small, moderately eccentric planet - such as Mars. We show that the structure is a result of a directed apsidal precession occurring in particles that migrate the planet’s orbital region under Poynting-Robertson drag. We further analyze the strength of this effect with respect to planet and particle parameters.

Chondrites are made of a mixture of solids formed at high and low temperatures. This heterogeneity was thought to be produced by large scale transport processes in the Sun’s isolated accretion disk. However, mounting evidences suggest that refractory inclusions in chondrites were produced together with the disk formation.

We present numerical simulations of the formation and transport of rocky materials during the collapse of the Solar Nebula’s parent cloud and the consequent disk assembling.

We find that the interplay between the cloud collapse, the dynamics of gas and dust and thermal processing of different species in the disk, results in a local mixing of solids with different thermal histories. Our simulations return an heterogeneous distribution of refractory material with higher concentration in the outer disk. This refractory material has a short formation timescales, during the first tens of kyr of the Sun (class 0-I). Our results open new frontiers into the origin of the compositional diversity of chondrites.

Meteoritic evidence shows that the Solar system at birth contained significant quantities of short-lived radioisotopes (SLRs) such as 60Fe and 26Al produced in supernova explosions and in the Wolf-Rayet winds. Explaining how they travelled from these origin sites to the primitive Solar system before decaying is an outstanding problem. In this paper, we present a chemo-hydrodynamical simulation of the entire Milky Way to measure for the distribution of 60Fe/56Fe and 26Al/27Al ratios over all stars in the Galaxy. We show that the Solar abundance ratios are well within the normal range. We find that SLRs are abundant in newborn stars because star formation is correlated on Galactic scales, so that ejecta preferentially enrich atomic gas that will subsequently be accreted onto existing GMCs or will form new ones. Thus new generations of stars preferentially form in patches of the Galaxy contaminated by previous generations of stellar feedback.

In this paper, a first study of the atmospheric entry of carbonate micrometeoroids, in an astrobiological perspective, is performed. Therefore an entry model, which includes two-dimensional dynamics, non-isothermal atmosphere, ablation and radiation losses, is build and benchmarked to literature data for silicate micrometeoroids. A thermal decomposition model of initially pure magnesium carbonate is proposed, and it includes thermal energy, mass loss and the effect of changing composition as the carbonate grain is gradually converted into oxide. Several scenarios are obtained by changing the initial speed, entry angle and grain diameter, producing a systematic comparison of silicate and carbonate grain. The results of the composite model show that the thermal behaviour of magnesium carbonate is markedly different from that of the corresponding silicate, much lower equilibration temperatures being reached in the first stages of the entry. At the same time, the model shows that the limit of a thermal protection scenario, based on magnesium carbonate, is the very high decomposition speed even at moderate temperatures, which results in the total loss of carbon already at about 100 km altitude. The present results show that, although decomposition and associated cooling are important effects in the entry process of carbonate grains, the specific scenario of pure MgCO3 micrograin does not allow complex organic matter delivery to the lower atmosphere. This suggests us to consider less volatile carbonates for further studies.

We present an update on our work on understanding the population of natural objects that are temporarily captured in the Earth-Moon system like the 2-3 meter diameter, 2006 RH120, that was discovered by the Catalina Sky Survey. We use the term ‘minimoon’ to refer to objects that are gravitationally bound to the Earth-Moon system, make at least one revolution around the barycenter in a co-rotating frame relative to the Earth-Sun axis, and are within 3 Earth Hill-sphere radii. There are one or two 1 to 2 meter diameter minimoons in the steady state population at any time, and about a dozen larger than 50 cm diameter. ‘Drifters’ are also bound to the Earth-Moon system but make less than one revolution about the barycenter. The combined population of minimoons and drifters provide a new opportunity for scientific exploration of small asteroids and testing concepts for in-situ resource utilization. These objects provide interesting challenges for rendezvous missions because of their limited lifetime and complicated trajectories. Furthermore, they are difficult to detect because they are small, available for a limited time period, and move quickly across the sky.

Some main-belt asteroids evolve into near-Earth objects. They can then experience the same meteoroid-producing phenomena as active asteroids in the main belt. If so, they would produce meteoroid streams, some of which evolve to intersect Earth's orbit and produce meteor showers at Earth. Only few of those are known. Meteoroid streams that move in orbits with Tisserand parameter well in excess of 3 are the Geminids and Daytime Sextantids of the Phaethon complex and the lesser known epsilon Pegasids. The observed activity appears to be related to nearly whole scale disintegrations, rather than dust ejection from volatile outgassing as observed in active comets. There is only a small population of asteroids with a main-belt origin that recently disintegrated into meteoroid streams.

On February 15, 2013, 3:20 UT, an asteroid of the size of about 19 meters and mass of 12,000 metric tons entered the Earth's atmosphere unexpectedly near the border of Kazakhstan and Russia. It was the largest confirmed Earth impactor since the Tunguska event in 1908. The body moved approximately westwards with a speed of 19 km s−1, on a trajectory inclined 18 degrees to the surface, creating a fireball of steadily increasing brightness. Eleven seconds after the first sightings, the fireball reached its maximum brightness. At that point, it was located less than 40 km south from Chelyabinsk, a Russian city of population more than one million, at an altitude of 30 km. For people directly underneath, the fireball was 30 times brighter than the Sun. The cosmic body disrupted into fragments; the largest of them was visible for another five seconds before it disappeared at an altitude of 12.5 km, when it was decelerated to 3 km s−1. Fifty six second later, that ~600 kg fragment landed in Lake Chebarkul and created a 8 m wide hole in the ice. Small meteorites landed in an area 80 km long and several km wide and caused no damage. The meteorites were classified as LL ordinary chondrites and were interesting by the presence of two phases, light and dark. More material remained, however, in the atmosphere forming a dust trail up to 2 km wide and extending along the fireball trajectory from altitude 18 to 70 km. The dust then circled the Earth within few days and formed a ring around the northern hemisphere. In Chelyabinsk and its surroundings a very strong blast wave arrived 90 – 150 s after the fireball passage (depending on location). The wave was produced by the supersonic flight of the body and broke ~10% of windows in Chelyabinsk (~40% of buildings were affected). More than 1600 people were injured, mostly from broken glass. The whole event was well documented by video cameras, seismic and infrasonic records, and satellite observations. The total energy was 500 kT TNT (2 × 1015 J).

Comets, asteroids, meteorites, micrometeorites, interplanetary dust particles (IDPs), and ultra-carbonaceous Antarctic micrometeorites (UCAMMs) may contain carbonaceous material, which was exogenously delivered to the early Earth. Carbonaceous chondrites have an enormous variety of extra-terrestrial compounds, including all the key compounds important in terrestrial biochemistry. Comets contain several carbon-rich species and, in addition, the hypervelocity impact-shock of a comet can produce several α-amino acids. The analysis of the carbonaceous content of extra-terrestrial matter provides a window into the resources delivered to the early Earth, which may have been used by the first living organisms.

The possibility that some meteoroids in the size range 1 – 20 meters are rubble piles i.e. assembles of boulders of various sizes held together only by small van der Waals forces, is investigated. Such meteoroids are expected to start disrupting into individual pieces during the atmospheric entry at very low dynamic pressures of ~ 25 Pa, even before the onset of ablation. The heterogeneous bodies as Almahata Sitta (asteroid 2008 TC3) and Benešov are primary candidates for rubble piles. Nevertheless, by analyzing the deceleration, wake, and light curve of the Benešov bolide, we found that the meteoroid disruption started only at a height of 70 km under dynamic pressure of 50 kPa. No evidence for a very early fragmentation was found also for the Chelyabinsk event.

Recent investigations on small asteroids, initiated by the Chelyabinsk event, are reviewed. New estimates of the terrestrial impact rate, importance of Sun-grazing conditions in the evolution of near-Earth objects, and problems associated with dangerous objects approaching the Earth from the Sun direction are discussed.

Yarkovsky-Radzievskij effect exceeds the Poynting-Robertson effect in the perturbing action on particles larger than 100 μm. We obtained formulae for averaged changes in a meteoroid's Keplerian orbital elements and used them to estimate dispersion in the Geminid meteoroid stream. It was found that dispersion in semi-major axis of the model shower increased nearly three times on condition that meteoroids rotation is fast, and the rotation axis is stable.

NEOs come close to the Earth's orbit so that any dust ejected from them, might be seen as a meteor shower. Orbits evolve rapidly, so that a similarity of orbits at one given time is not sufficient to prove a relationship, orbital evolution over a long time interval also has to be similar. Sporadic meteoroids can not be associated with a single parent body, they can only be classified as cometary or asteroidal. However, by considering one parameter criteria, many sporadics are not classified properly therefore two parameter approach was proposed.

Asteroids 3200 Phaethon and 196256 (2003 EH1) are connected with two major meteoroid streams, Geminids and Quadrantids, respectively. We have modeled the observed light curves and decelerations of Geminid and Quadrantid meteors and studied their spectra. In both cases, we have found typical bulk densities of about 2600 kg m−3, much larger than in cometary meteoroids. Sodium was partially lost from Geminids and Quadrantids due to solar heating. The Quadrantid material was therefore not hidden deep inside the parent body 1500 years ago, when the perihelion was low enough for sodium loss to occur.

The lunar regolith (soil) has recorded a history of the early Moon, the Earth, and the entire solar system. A major goal of the developing lunar exploration program should be to find and play back existing fragments of that tape. By playing back the lunar tape, we can uncover a record of planetary bombardment, as well as solar and stellar variability. The Moon can tell us much about our place in the solar system and in the Universe. The lunar regolith has likely recorded the original meteoritic bombardment of Earth and Moon, a violent cataclysm that may have peaked around 4 GY, and the less intense bombardment occurring since that time. Decrease in bombardment allowed life to develop on Earth. This impact history is preserved as megaregolith layers, ejecta layers, impact melt rocks, and ancient impact breccias. The impact history for the Earth and Moon possibly had profound effects on the origin and development of life. Life may have arrived via meteorite transport from a more quiet body, such as Mars. The solar system may have experienced bursts of severe radiation from the Sun, other stars or from unknown sources. The lunar regolith has also recorded a radiation history in the form of implanted and trapped solar wind and solar flare materials and radiation damage. The Moon can be considered as a giant tape recorder containing the history of the solar system. Lunar soil generated by small impacts will be found sandwiched between layers of basalt or pyroclastic deposits. This filling constitutes a buried time capsule that is likely to contain well-preserved ancient regolith. Study of such samples will show us how the solar system has evolved and changed over time. The lunar recording can provide detailed snapshots of specific portions of solar and stellar variability.

It is shown, that the explosion of the bolide above the Mediterranean sea on July, 6th 2002 with a high probability was a fragment of an icy cometary nucleus which initial weight was equal approximately to 7 ⋅ 108 grams. This follows from the determined energy of the outburst equal to 26kT of TNT (Brown et al. 2002). We think that this energy refers to the height of the maximal braking of the body in the Earth's atmosphere. At the speed of 20.3 km/s accepted by authors, the weight of a body at this height is equal 5 ⋅ 108 gr, and at the entrance in the atmosphere it was approximately of 7 ⋅ 108 gr.

The first asteroid to be discovered in space and subsequently observed to impact Earth, asteroid 2008 TC3, exploded at a high 37 km altitude and stopped ablating at 32 km. This would classify the fireball as of Ceplecha's PE-criterion IIIb/a, meaning “cometary” in nature. In this case, the structural weakness may have come from pores found in some of the recovered meteorites, called “Almahata Sitta” (= Station 6 in Arabic). The explosion turned most of the asteroid mass to dust and vapor, only a tiny fraction shattered into macroscopic meteorites, the heaviest of which was 283 gram. Other similarly frail asteroids may be related to main belt comets.

In 2007-2008 the authors found many magnetite microspheric particles in ground samples at the Trans-Carpathians mountains near the village of Tur'yi Remety. Their diameters are of 0.1 - 0.3 mm and they have Ni, Co and Cr as chemical composition. We think that these particles are part of the bright bolide of EN171101 which exploded above Trans-Carpathians mountains on Nov. 17, 2001.

We have tested the reliability of various meteoroid streams identification methods. We used a numerically generated set of meteoroid orbits (a stream component and a sporadic background) that were searched for streams using several methods.

We discuss using high solar cycle atmospheric conditions as sensors for observing meteors and their properties. High altitude meteor trails (HAMTs) have sometimes been observed with HPLA (High Power Large Aperture) radars. At other times they are not seen. In the absence of systematic studies on this topic, we surmise that the reason might be differing atmospheric conditions during the observations. At EISCAT HAMTs were observed in 1990 and 1991. Very high meteor trails were observed with Israeli L-band radars in 1998, 1999 and 2001. Through the Leonid activity, around the latest perihelion passage of comet Tempel-Tuttle, optical meteors as high as 200 km were reported. This was partly due to new and better observing methods. However, all the reported periods of high altitude meteors seem to correlate with solar cycle maximum. The enhanced atmospheric and ionospheric densities extend the meteoroid interaction range with the atmosphere along its path, offering a better possibility to distinguish differential ablation of the various meteoric constituents. This should be studied during the next solar maximum, due within a few years.

External energy inputs into all planetary upper atmospheres (including more than a half dozen moons with atmospheres) are comprised of combinations of solar EUV, soft x-rays, solar energetic particles, solar wind charged particles, magnetospherically accelerated particles, solar wind electric field, interplanetary dust particles as well as propagating lower atmosphere disturbances. Each input has analogous physical interactions with all planetary ionospheres and upper atmospheres, but the integrated consequences of the multiple energy inputs vary from planet to planet. The Earth forms the framework for most fundamental processes because of extensive measurements of the effects of each of the inputs. However the conditions at Earth are far different from those at the carbon dioxide atmosphere of magnetic field-free, slow-rotating Venus, the carbon dioxide atmosphere of Mars with patchy remnant magnetic fields, while the outer planets have hydrogen atmospheres, are fast rotating with intrinsic magnetic fields, and encompass moons that interact with the magnetospheres and have exotic atmospheres. Although the physical processes are known, our understanding of our solar system's ionospheres diminishes with increasing distance from the Sun.