90 research outputs found
Discovery of a new branch of the Taurid meteoroid stream as a real source of potentially hazardous bodies
Taurid meteor shower produces prolonged but usually low activity every
October and November. In some years, however, the activity is significantly
enhanced. Previous studies based on long-term activity statistics concluded
that the enhancement is caused by a swarm of meteoroids locked in 7:2 resonance
with Jupiter. Here we present precise data on 144 Taurid fireballs observed by
new digital cameras of the European Fireball Network in the enhanced activity
year 2015. Orbits of 113 fireballs show common characteristics and form
together a well defined orbital structure, which we call new branch. We found
that this branch is characterized by longitudes of perihelia lying between
155.9-160o and latitudes of perihelia between 4.2-5.7o. Semimajor axes are
between 2.23-2.28 AU and indeed overlap with the 7:2 resonance. Eccentricities
are in wide range 0.80-0.90. The orbits form a concentric ring in the inner
solar system. The masses of the observed meteoroids were in a wide range from
0.1 g to more than 1000 kg. We found that all meteoroids larger than 300 g were
very fragile, while those smaller than 30 g were much more compact. Based on
orbital characteristics, we argue that asteroids 2015 TX24 and 2005 UR, both of
diameters 200-300 meters, are direct members of the new branch. It is therefore
very likely that the new branch contains also numerous still not discovered
objects of decameter or even larger size. Since asteroids of sizes of tens to
hundreds meters pose a treat to the ground even if they are intrinsically weak,
impact hazard increases significantly when the Earth encounters the Taurid new
branch every few years. Further studies leading to better description of this
real source of potentially hazardous objects, which can be large enough to
cause significant regional or even continental damage on the Earth, are
therefore extremely important.Comment: 24 pages, 22 figures, 5 tables. Accepted in Astronomy and
Astrophysic
Orbital evolution of P\v{r}\'{i}bram and Neuschwanstein
The orbital evolution of the two meteorites P\v{r}\'{i}bram and
Neuschwanstein on almost identical orbits and also several thousand clones were
studied in the framework of the N-body problem for 5000 years into the past.
The meteorites moved on very similar orbits during the whole investigated
interval. We have also searched for photographic meteors and asteroids moving
on similar orbits. There were 5 meteors found in the IAU MDC database and 6
NEAs with currently similar orbits to P\v{r}\'{i}bram and Neuschwanstein.
However, only one meteor 161E1 and one asteroid 2002 QG46 had a similar orbital
evolution over the last 2000 years.Comment: 7 pages, 2 figures, 3 table
Heavy Metal Contamination of the Loučka River Water Ecosystem
Heavy metal contamination of the Loučka River water ecosystem was assessed in July 2005. We analyzed concentrations of T-Hg (total mercury), Cd, Pb, Cr, Cu, Zn, and Ni in water, sediments, zoobenthos, and in the brown trout (Salmo trutta m. fario) muscle and liver tissues (a total of 28 individuals) at four sampling sites. The highest Pb and Ni concentrations (4.634-12.050 and 0.689-24.980 mg kg-1) were found in sediments. The zoobenthos was most contaminated by Zn and Cu (0.556-1.505 and 2.925-74.300 mg kg-1). The heavy metal contamination of river water was highest in Ni and Cr (0.1-6.8 and 0.5-10.0 mg l-1). Concentrations of heavy metals in the brown trout muscle were following (in mg kg-1): Pb 0.108 ± 0.073 - 1.010 ± 0.506, Cd 0.003 ± 0.002 - 0.026 ± 0.022, Zn 3.956 ± 0.371 - 5.801 ± 1.718, Ni 0.058 ± 0.018 - 0.102 ± 0.046, Cr 0.028 ± 0.005 - 0.073 ± 0.039, Cu 0.329 ± 0.079 - 0.437 ± 0.064 and Hg 0.065 ± 0.008 - 0.106 ± 0.047. Statistical differences (P -1). Humans of 60 kg body mass may consume 1.5 kg of brown trout muscle from the Loučka River weekly without any risk. Adverse influence of the Uniglas distillery on the Loučka River environment contamination by heavy metals was not confirmed
Atmospheric trajectories and light curves of shower meteors
Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe
Tidal disruption of NEAs - a case of P\v{r}\'ibram
This work studies the dynamical evolution of a possible meteor stream along
the orbit of the P\v{r}\'{i}bram meteorite, which originated in the tidal
disruption of the putative rubble-pile-like parent body during a close approach
to the Earth. We assumed the disruption at the time when the ascending or
descending node of the parent orbit was close to the Earth's orbit. In the last
5000 years, the P\v{r}\'{i}bram orbit has crossed the Earth orbit twice. It
happened about 4200 years and 3300 years ago. In both cases, we modeled the
release of particles from the simplified model of rotating asteroid, and traced
their individual orbital evolution to the current date. It takes several
hundred years to spread released meteoroids along the entire orbit of the
parent body. Even today, the stream would be relatively narrow.
Considering a model parent body with physical parameters of the asteroid
Itokawa, the complete disintegration of the object produced 3.8
meteoroid particles with diameter 1\,cm. The meteor activity observed
from the Earth is revealed and justification of follow-up observation during
suggested activity of the shower in the first two weeks of April is discussed.
The Earth's tidal forces would disintegrate a fraction of NEA population into
smaller objects. We evaluate the upper limit of mass of disintegrated asteroids
within the mean NEA lifetime and the contribution of disrupted matter to the
size distribution of the NEA.Comment: 8 pages, 10 figure
Trajectory and orbit of the unique carbonaceous meteorite Flensburg
Stars and planetary system
Fault-tolerant formation driving mechanism designed for heterogeneous MAVs-UGVs groups
A fault-tolerant method for stabilization and navigation of 3D heterogeneous formations is proposed in this paper. The presented Model Predictive Control (MPC) based approach enables to deploy compact formations of closely cooperating autonomous aerial and ground robots in surveillance scenarios without the necessity of a precise external localization. Instead, the proposed method relies on a top-view visual relative localization provided by the micro aerial vehicles flying above the ground robots and on a simple yet stable visual based navigation using images from an onboard monocular camera. The MPC based schema together with a fault detection and recovery mechanism provide a robust solution applicable in complex environments with static and dynamic obstacles. The core of the proposed leader-follower based formation driving method consists in a representation of the entire 3D formation as a convex hull projected along a desired path that has to be followed by the group. Such an approach provides non-collision solution and respects requirements of the direct visibility between the team members. The uninterrupted visibility is crucial for the employed top-view localization and therefore for the stabilization of the group. The proposed formation driving method and the fault recovery mechanisms are verified by simulations and hardware experiments presented in the paper
Exploring the Bimodal Solar System via Sample Return from the Main Asteroid Belt: The Case for Revisiting Ceres
Abstract: Sample return from a main-belt asteroid has not yet been attempted, but appears technologically feasible. While the cost implications are significant, the scientific case for such a mission appears overwhelming. As suggested by the “Grand Tack” model, the structure of the main belt was likely forged during the earliest stages of Solar System evolution in response to migration of the giant planets. Returning samples from the main belt has the potential to test such planet migration models and the related geochemical and isotopic concept of a bimodal Solar System. Isotopic studies demonstrate distinct compositional differences between samples believed to be derived from the outer Solar System (CC or carbonaceous chondrite group) and those that are thought to be derived from the inner Solar System (NC or non-carbonaceous group). These two groups are separated on relevant isotopic variation diagrams by a clear compositional gap. The interface between these two regions appears to be broadly coincident with the present location of the asteroid belt, which contains material derived from both groups. The Hayabusa mission to near-Earth asteroid (NEA) (25143) Itokawa has shown what can be learned from a sample-return mission to an asteroid, even with a very small amount of sample. One scenario for main-belt sample return involves a spacecraft launching a projectile that strikes an object and flying through the debris cloud, which would potentially allow multiple bodies to be sampled if a number of projectiles are used on different asteroids. Another scenario is the more traditional method of landing on an asteroid to obtain the sample. A significant range of main-belt asteroids are available as targets for a sample-return mission and such a mission would represent a first step in mineralogically and isotopically mapping the asteroid belt. We argue that a sample-return mission to the asteroid belt does not necessarily have to return material from both the NC and CC groups to viably test the bimodal Solar System paradigm, as material from the NC group is already abundantly available for study. Instead, there is overwhelming evidence that we have a very incomplete suite of CC-related samples. Based on our analysis, we advocate a dedicated sample-return mission to the dwarf planet (1) Ceres as the best means of further exploring inherent Solar System variation. Ceres is an ice-rich world that may be a displaced trans-Neptunian object. We almost certainly do not have any meteorites that closely resemble material that would be brought back from Ceres. The rich heritage of data acquired by the Dawn mission makes a sample-return mission from Ceres logistically feasible at a realistic cost. No other potential main-belt target is capable of providing as much insight into the early Solar System as Ceres. Such a mission should be given the highest priority by the international scientific community
Estimation of digestibility of nutrients in feed mixtures for carp (Cyprinus carpio L.) fry when using chromium oxide as an indicator
In years 1990-1991, laboratory experiments were carried out to estimate values of coefficients of apparent digestibility in two genetic lines of carp fry: a scaly form (HoS) with initial weight of 37 g and a scattered form (HoL) with initial weight of 49 g. Experiments were carried out at the water temperature of 20°C. Two feeding mixtures were tested, viz. S1 and S2 with 19 and 34% of protein. The obtained coefficients of apparent digestibility of crude protein, crude fat, N-free extract and crude fibre ranged from 75.6 to 87.2%, from 32.2 to 67.8%, from 58.2 to 67.8% and from 0.9 to 14.3%, respectively. Better values of food conversion were found in the scaly form of carp fry (proteins, fat and carbohydrates by 5.9 and 29.4 and 8.23%, respectively)
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