Orbital characterization of superbolides observed from space: dynamical association with near-Earth objects, meteoroid streams and identification of hyperbolic meteoroids

There is an unceasing incoming flux of extraterrestrial materials reaching the Earth's atmosphere. Some of these objects produce luminous columns when they ablate during the hypersonic encounter with air molecules. A few fireballs occur each year bright enough to be detected from space. The source of these events is still a matter of debate, but it is generally accepted that they are of sporadic origin. We studied the NASA-JPL Center for NEOs Studies (CNEOS) fireball database to infer the dynamic origin of large bolides produced by meter-sized projectiles that impacted our planet. These likely meteorite-dropping events were recorded by the US Government satellite sensors. We estimated the false-positive rate and analyzed the time evolution of multiple orbit dissimilarity criteria concerning potential associations with near-Earth objects and meteoroid streams. We found that at least 16% of the large bolides could be associated with meteoroid streams, about 4% are likely associated with near-Earth asteroids, and 4% may be linked to near-Earth comets. This implies that a significant fraction of meter-sized impactors producing large bolides may have an asteroidal or cometary origin. In addition, we found at least three bolides having hyperbolic orbits with high tensile strength values. Meter-sized meteoroids of interstellar origin could be more common than previously thought, representing about 1% of the flux of large bolides. The inferred bulk physical properties suggest that the interstellar medium could bias these projectiles towards high strength rocks with the ability to survive prolonged exposure to the harsh interstellar space conditions.Comment: Accepted for publication in The Astronomical Journal (AAS38905R1

Lipid Oxidation Inhibition in Frozen Farmed Salmon (Oncorhynchus kisutch ): Effect of Packaging

3 pages, 1 table.Coho salmon (Oncorhynchus kisutch) has recently attracted a great interest as a farmed product. This research focuses on its commercialisation as a frozen product. For it, an advanced storage technology combining vacuum and a polyphenolic rich-film was applied for a 9-months storage period (–18°C). The study was addressed to lipid hydrolysis and oxidation changes and to endogenous antioxidant content in salmon muscle. No effect of packaging conditions could be observed on free fatty acid formation. However, vacuum packaging conditions provided a partial inhibition of primary (peroxide) and secondary (anisidine value) lipid oxidation development; this inhibitory effect was accompanied by a lower tocopherol isomers loss. The employment of a film including polyphenolic compounds led to a partial inhibition of α-tocopherol breakdown and to a lower secondary (anisidine value) and tertiary (fluorescent compound formation) lipid oxidation development. A partial inhibitory effect on lipid oxidation development is concluded for the employment of a polyphenolic compound rich-film packaging when applied to farmed coho salmon.This research was carried out in the frame of the Project No. 2006 CL 0034 (2007–2008), granted by the U. Chile-CSIC Cooperation Program. Coho salmon fish was provided by Aquachile SA (Puerto Montt, Chile).Peer reviewe

On the chemical nature and orbit of meteoroids from the omicron draconid stream

The omicron Draconids were first observed by Denning in the 19th Century [1]. The activity was, however, modest, with a zenithal hourly rate (ZHR) of about 10–12. Denning [2] also reported observations in 1929 but in neither case was an orbit given, only a radiant position (RA ~271º, Dec. ~60º). However, for a considerable time after Denning’s observations, no records of any activity exist. Whether this is due to a lack of observers at the pertinent time (early July and thus close to the longest day and also close to the activity period of the delta Aquariids and observers may have preferred to study those) or an intrinsic lack of activity from the Omicron Draconids is not clear. The next record appears to be by Cook et al. [3] reporting on the work of the Harvard Meteor Project in the 1950s. In that paper they also suggested that the formation of the stream was associated with the disintegration of the nucleus of comet C/1919 Q2 Metcalf. In fact, our team recorded in 2008 a mag. -18 omicron Draconid fireball which was linked to this comet [4]. Here we present the analysis of a doublestation omicron-Draconid fireball recorded in the framework of our continuous fireball monitoring and spectroscopic campaigns in July 2007. The unique spectrum obtained for a member of this stream has provides helpful information about the chemical nature of meteoroids in the omicron-Draconid stream

Characterisation of Medipix3 Silicon Detectors in a Charged-Particle Beam

While designed primarily for X-ray imaging applications, the Medipix3 ASIC can also be used for charged-particle tracking. In this work, results from a beam test at the CERN SPS with irradiated and non-irradiated sensors are presented and shown to be in agreement with simulation, demonstrating the suitability of the Medipix3 ASIC as a tool for characterising pixel sensors.Comment: 16 pages, 13 figure

Outburst activity in comets: II. A multi-band photometric monitoring of comet 29p/Schwassmann-Wachmann 1

We have carried out a continuous multi-band photometric monitoring of the nuclear activity of comet 29P/Schwassmann-Wachmann 1 from 2008 to 2010. Our main aim has been to study the outburst mechanism on the basis of a follow-up of the photometric variations associated with the release of dust. We used a standardized method to obtain the 10 arc-sec nucleus photometry in the V, R, and I filters of the Johnson-Kron-Cousins system, being accurately calibrated with standard Landolt stars. Production of dust in the R and I bands during the 2010 Feb. 3 outburst has been also computed. We conclude that the massive ejection of large (optically-thin) particles from the surface at the time of the outburst is the triggering mechanism to produce the outburst. Ulterior sublimation of these ice-rich dust particles during the following days induces fragmentation, generating micrometer-sized grains that increase the dust spatial density to produce the outburst in the optical range due to scattering of sun light. The material leaving the nucleus adopts a fan-like dust feature, formed by micrometer-sized particles that are decaying in brightness as it evolved outwards. By analyzing the photometric signal measured in a standardized 10-arcsec aperture using the Phase Dispersion Minimization technique we have found a clear periodicity of 50 days. Remarkably, this value is also consistent with an outburst frequency of 7.4 outbursts/year deduced from the number of outbursts noticed during the effective observing time.Comment: 19 pages, 3 Tables, and 6 figure

A meteorite-dropping superbolide from the catastrophically disrupted comet C1919Q2 Metcalf: a pathway for meteorites from Jupiter family comets

2 pages, 1 figure.-- Contributed to: 40th Lunar and Planetary Science Conference (The Woodlands, Texas ,Mar 23-27, 2009).It is widely accepted that cometary nuclei are composed of a mix of volatile ices and meteoritic materials. In a series of seminal papers F. L. Whipple tried to explain how the irregular internal structure of each nuclei would be able to explain the nongravitational forces, and how the continuous sublimation of the ice species would lead to explain the origin of meteoroid streams. Not essential progress was made until that the approach of a cruise of international spacecrafts to comet 1P/Halley allowed to achieve the first direct view of a cometary nucleus.Peer reviewe

A meteorite-dropping superbolide from the catastrophycally disrupted comet C1919Q2 metcalf : a pathway for meteorites from jupiter family comets

It is widely accepted that cometary nu- clei are composed of a mix of volatile ices and meteor- itic materials. In a series of seminal papers F. L. Whipple tried to explain how the irregular internal structure of each nuclei would be able to explain the nongravitational forces, and how the continuous sub- limation of the ice species would lead to explain the origin of meteoroid streams [1,2,3]. Not essential pro- gress was made until that the approach of a cruise of international spacecrafts to comet 1P/Halley allowed to achieve the first direct view of a cometary nucleus [4]. At that time several models were built to explain the main features observed in 1P/Halley nucleus under the main concept that cometary nuclei were born from the accretion of weakly bounded ice-rich cometesimals [5, 6]. A similar view was extracted from the 81P/Wild 2 fragile aggregates recovered by Stardust mission [7]. Obviously, particles recollected in the coma of a comet are biased towards those fragile aggregates that are lifted off from ice-rich regions by the sublimated gas drag. Many cometary meteoroid streams crossing the Earth were formed in this way, but not all. Catastro- phic disruption of cometary nuclei is also a regular mechanism of producing meteoroid streams [8, 9, 10]. Interestingly, this mechanism is able to produce large boulders as observed e.g. during the disruption of comet C/1999 S4 LINEAR [11]. It was believed that the large fragments released by these break-up events will proceed to faint in the coma due to suffer a cas- cade fragmentation. Obviously remote observations are not able to decipher if the final product of these events are mm- or m-sized meteoroids. In a recent pa- per [12] we identified a meter-sized meteoroid that was probably produced during the disintegration of comet C1919Q2 Metcalf. It produced a very bright fireball, with a maximum brightness of magn. –18 that was observed over much of Spain as well as parts of Portugal, and France on July 11, 2008 at 21:17:39 UTC. Fortuitously, it flew over many of the instru- ments operated by the SPanish Meteor and Fireball Network (SPMN) so that accurate measurements of its properties were recorded. Here we summarize both these observations and the deductions made from them regarding the nature and origin of the body that gave rise to this fireball

The 2011 October Draconids outburst. I. Orbital elements, meteoroid fluxes and 21P/Giacobini-Zinner delivered mass to Earth

On October 8th, 2011 the Earth crossed the dust trails left by comet 21P/Giacobini-Zinner during its XIX and XX century perihelion approaches with the comet being close to perihelion. The geometric circumstances of that encounter were thus favorable to produce a meteor storm, but the trails were much older than in the 1933 and 1946 historical encounters. As a consequence the 2011 October Draconid display exhibited several activity peaks with Zenithal Hourly Rates of about 400 meteors per hour. In fact, if the display had been not forecasted, it could have passed almost unnoticed as was strongly attenuated for visual observers due to the Moon. This suggests that most meteor storms of a similar nature could have passed historically unnoticed under unfavorable weather and Moon observing conditions. The possibility of obtaining information on the physical properties of cometary meteoroids penetrating the atmosphere under low-geocentric velocity encounter circumstances motivated us to set up a special observing campaign. Added to the Spanish Fireball Network wide-field all-sky and CCD video monitoring, other high-sensitivity 1/2" black and white CCD video cameras were attached to modified medium-field lenses for obtaining high resolution orbital information. The trajectory, radiant, and orbital data of 16 October Draconid meteors observed at multiple stations are presented. The results show that the meteors appeared from a geocentric radiant located at R.A.=263.0+-0.4 deg. and Dec.=+55.3+-0.3 deg. that is in close agreement with the radiant predicted for the 1873-1894 and the 1900 dust trails. The estimated mass of material from 21P/Giacobini-Zinner delivered to Earth during the six-hours outburst was around 950+-150 kg.Comment: Manuscript in press in Monthly Notices of the Royal Astronomical Society, submitted to MNRAS on November 16th, 2012 Accepted for publication in MNRAS on April 28th, 2013 Manuscript Pages: 21 Tables: 8 Figures: 4 Manuscript associated: "The 2011 October Draconids outburst. II. Meteoroid chemical abundances from fireball spectroscopy" by J.M. Madiedo is also in press in the same journa