Dust Ejection Research Articles

Dust composition and mass-loss return from the luminous blue variable R71 in the LMC

We present an analysis of mid-and far-infrared (IR) spectrum and spectral energy distribution (SED) of the LBV R71 in the LMC.This work aims to understand the overall contribution of high-mass LBVs to the total dust-mass budget of the interstellar medium (ISM) of the LMC and compare this with the contribution from low-mass asymptotic giant branch (AGB) stars. As a case study, we analyze the SED of R71. We compiled all the available photometric and spectroscopic observational fluxes from various telescopes for a wide wavelength range (0.36 -- 250\,$\mu$m). We determined the dust composition from the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate, and other dust shell properties by modeling the SED of R71. We noted nine spectral features in the dust shell of R71 by analyzing Spitzer spectroscopic data. Among these, we identified three new crystalline silicate features. We computed our model spectrum by using 3D radiative transfer code MCMax. Our model calculation shows that dust is dominated by amorphous silicates, with some crystalline silicates, metallic iron, and a very tiny amount of polycyclic aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01 M$_\odot$, from which we arrive at a total ejected mass of $\approx$ 5 M$_\odot$. This implies a time-averaged dust mass-loss rate of 2.5$\times$10$^{-6}$ M$_\odot$\,yr$^{-1}$ with an explosion about 4000 years ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass at a similar rate, and estimate the total contribution to the mass budget of the LMC to be $\approx$ 10$^{-5}$ M$_\odot$\,yr$^{-1}$, which is comparable to the contribution by all the AGB stars in the LMC. Based on our analysis on R71, we speculate that LBVs as a class may be an important dust source in the ISM of the LMC.

Mass loading of the solar wind by a sungrazing comet

AbstractCollisionless mass loading was suggested by Biermann et al. (1967) for describing interactions between the solar wind and cometary atmospheres. Recent observations have led to an increased interest in coronal mass loading due to sungrazing comets and collisional debris of sunward migrating interplanetary dust particles. In a previous paper, we presented a 3‐D MHD model of the solar corona based on the Block‐Adaptive‐Tree‐Solarwind‐Roe‐Upwind‐Scheme code which includes the interaction of dust with the solar wind. We have shown the impact on the solar wind from abrupt mass loading in the coronal region. We apply the model to a sungrazing cometary source, using ejected dust dynamics to generate tail‐shaped mass‐loading regions. Results help predict the effects on the solar wind acceleration and composition due to sungrazing comets, such as Comet C/2011 W3 (Lovejoy). We show how these effects may be detected by the upcoming Solar Probe Plus Mission.

Spectroscopic Observations of the 2011 Draconids Meteor Shower

Some past October Draconid shower meteoroids fell apart in a spray of fragments at the end of their trajectory before slowing down, from which it was concluded that these were among the most fragile meteoroids known. In those instances, the dust could not be reliably traced to a particular return of the parent comet 21P/Giaconini-Zinner. On October 8th, 2011, Earth was predicted to transverse the 1900 A.D. dust ejecta of the comet. In 1900, the comet’s perihelion distance first moved significantly inwards to the Sun and ejection conditions could have been unusual. An airborne observing campaign was organized, with several teams contributing imaging and spectrographic cameras to study the manner in which these meteoroids released the volatile element sodium during the ablation process in the Earth’s atmosphere. IMCCE, ESA, and the SETI Institute contributed spectrographic cameras based on low-light WATEC 902H2 Ultimate, low-light LCC1, and GenII XX1332 image intensified cameras. An outburst was observed, much as predicted. Despite a lack of bright meteors, a total of 15 Draconid spectra were recorded. All show evidence of an early release of sodium. The loss of sodium was observed to coincide with the formation of a distinct wake of fragments. The observations show that 21P/Giacobini-Zinner ejected fragile meteoroids during the return in 1900. Those grains may have lost some sodium even before impacting Earth.

Tungsten damage and melt losses under plasma accelerator exposure with ITER ELM relevant conditions

Experimental simulations of ITER edge-localized mode have been performed with a Kh-50 quasi-stationary plasma accelerator. Heat loads exceeded the tungsten melting threshold. Droplet splashing and the solid dust ejection were observed. Droplets were emitted during the plasma exposure and dust generation dominated after the end of a plasma pulse, at the time of the material cooling. A decrease in the droplet velocity at an increase in the surface heat load was observed. It could be attributed to growing sizes of the droplets at higher energy loads. After one hundred pulses were performed at loads below the tungsten melting and above the cracking threshold, some porosity appeared. Such defects achieved dimensions of several tens of μm. A heat load amounting to half the cracking threshold (0.3 MJ m−2) could lead to the appearance of fatigue cracks after 100 plasma pulses. In this case the appearance of cracks could be caused by the accumulation and redistribution of linear defects (dislocations) in the affected tungsten layer.

Tungsten Melt Losses under QSPA Kh-50 Plasma Exposures Simulating ITER ELMs and Disruptions

Experimental simulations of ITER transient events with surface heat load parameters relevant to edge-localized-mode (ELM) impacts and disruptions have been performed with a quasi-stationary plasma accelerator Kh-50. In the ELM simulation experiments with heat loads exceeding the tungsten melting threshold, both droplet splashing and solid dust ejection are observed. The erosion products emitted from the exposed tungsten surfaces in the form of droplets and solid dust have been clearly distinguished by variation of impacting heat load with performed analysis of particle ejection start time, their velocities, and changes in the luminosity of the particle traces in front of the target surface recorded with a charge-coupled device. Droplets are emitted during plasma exposure, and dust generation dominates after the end of the plasma pulse, at the time of the following material cooling. The contributions of Kelvin-Helmholtz instabilities to droplet splashing from the melt layer are discussed. Decrease of droplet velocity with increasing surface heat load is observed. This decrease could be attributed to the growing size of the droplets for higher energy loads.

Comets formed in solar-nebula instabilities! – An experimental and modeling attempt to relate the activity of comets to their formation process

When comet nuclei approach the Sun, the increasing energy flux through the surface layers leads to sublimation of the underlying ices and subsequent outgassing that promotes the observed emission of gas and dust. While the release of gas can be straightforwardly understood by solving the heat-transport equation and taking into account the finite permeability of the ice-free dust layer close to the surface of the comet nucleus, the ejection of dust additionally requires that the forces binding the dust particles to the comet nucleus must be overcome by the forces caused by the sublimation process. This relates to the question of how large the tensile strength of the overlying dust layer is. Homogeneous layers of micrometer-sized dust particles reach tensile strengths of typically 103 to 104Pa. This exceeds by far the maximum sublimation pressure of water ice in comets. It is therefore unclear how cometary dust activity is driven.To solve this paradox, we used the model by Skorov and Blum (Skorov, Y.V., Blum, J. 2012. Icarus 221, 361–11), who assumed that cometesimals formed by gravitational instability of a cloud of dust and ice aggregates and calculated for the corresponding structure of comet nuclei tensile strength of the dust-aggregate layers on the order of 1Pa. Here we present evidence that the emitted cometary dust particles are indeed aggregates with the right properties to fit the model by Skorov and Blum. Then we experimentally measure the tensile strengths of layers of laboratory dust aggregates and confirm the values derived by the model. To explain the comet activity driven by the evaporation of water ice, we derive a minimum size for the dust aggregates of ∼1mm, in agreement with meteoroid observations and dust-agglomeration models in the solar nebula. Finally we conclude that cometesimals must have formed by gravitational instability, because all alternative formation models lead to higher tensile strengths of the surface layers.

Windblown fugitive dust emissions from smelter slag

The waste products of mining and smelter operations contain fine particles that, when stored in stockpiles and tailings ponds, are subject to aerodynamic forces that may result in their suspension and transport within boundary layer air flows. The accuracy of atmospheric dispersion models such as AERMOD depends strongly upon suitable inputs for the emission rate that generally must be either measured or estimated from suitable analogues. Measurements of the emission rate of PM10 from smelter slag, based on wind tunnel experiments using the control volume method, are reported in this study and compared with vertical flux values obtained using a finite difference approximation. As compared to natural soils, the dust coatings on slag fragments are rapidly depleted during wind events so that the temporal aspect is important to capture in any consideration of the emission rate. At low wind speeds, vertical flux measurements underestimate the emission rate, but otherwise the agreement is excellent. Comparison with field measurements obtained at the smelter site reveals a degree of overlap with the laboratory data. As a general rule, PM10 emission from smelter slag by aerodynamic entrainment alone is several orders of magnitude lower than published fluxes of total suspended particulate (TSP) emitted from natural soil surfaces for which saltation bombardment is recognized to play a key role in the ejection of dust.

Relating jet structure to photometric variability: the Herbig Ae star HD 163296

Herbig Ae/Be stars are intermediate-mass pre-main sequence stars surrounded by circumstellar dust disks. Some are observed to produce jets, whose appearance as a sequence of shock fronts (knots) suggests a past episodic outflow variability. This "jet fossil record" can be used to reconstruct the outflow history. We present the first optical to near-infrared (NIR) VLT/X-shooter spectra of the jet from the Herbig Ae star HD 163296. We determine physical conditions in the knots, as well as their kinematic "launch epochs". Knots are formed simultaneously on either side of the disk, with a regular interval of ~16 yr. The velocity dispersion versus jet velocity and the energy input are comparable in both lobes. However, the mass loss rate, velocity, and shock conditions are asymmetric. We find Mjet/Macc ~ 0.01-0.1, consistent with magneto-centrifugal jet launching models. No evidence for dust is found in the high-velocity jet, suggesting it is launched within the sublimation radius (<0.5 au). The jet inclination measured from proper motions and radial velocities confirms it is perpendicular to the disk. A tentative relation is found between the structure of the jet and the photometric variability of the source. Episodes of NIR brightening were previously detected and attributed to a dusty disk wind. We report for the first time significant optical fadings lasting from a few days up to a year, coinciding with the NIR brightenings. These are likely caused by dust lifted high above the disk plane; this supports the disk wind scenario. The disk wind is launched at a larger radius than the high-velocity atomic jet, although their outflow variability may have a common origin. No significant relation between outflow and accretion variability could be established. Our findings confirm that this source undergoes periodic ejection events, which may be coupled with dust ejections above the disk plane.

Continued activity in P/2013 P5 PANSTARRS

The object P/2013 P5 PANSTARRS was discovered in August 2013, displaying a cometary tail, but its orbital elements indicated that it was a typical member of the inner asteroid main belt. We monitored the object from 2013 August 30 until 2013 October 05 using the CFHT 3.6 m telescope (Mauna Kea, HI), the NTT (ESO, La Silla), the CA 1.23 m telescope (Calar Alto), the Perkins 1.8m (Lowell) and the 0.6 m TRAPPIST telescope (La Silla). We measured its nuclear radius to be r < 0:25 0:29 km, and its colours g 0 r 0 = 0:58 0:05 and r 0 i 0 = 0:23 0:06, typical for an S-class asteroid, as expected for an object in the inner asteroid belt and in the vicinity of the Flora collisional family. We failed to detect any rotational light curve with an amplitude <0.05 mag and a double-peaked rotation period <20 h. The evolution of the tail during the observations was as expected from a dust tail. A detailed Finson-Probstein analysis of deep images acquired with the NTT in early September and with the CFHT in late September indicated that the object was active since at least late January 2013 until the time of the latest observations in 2013 September, with at least two peaks of activity around 2013 June 14 10 d and 2013 July 22 3 d. The changes of activity level and the activity peaks were extremely sharp and short, shorter than the temporal resolution of our observations ( 1 d). The dust distribution was similar during these two events, with dust grains covering at least the 1‐1000 m range. The total mass ejected in grains <1 mm was estimated to be 3:0 10 6 kg and 2:6 10 7 kg around the two activity peaks. Rotational disruption cannot be ruled out as the cause of the dust ejection. We also propose that the components of a contact binary might gently rub and produce the observed emission. Volatile sublimation might also explain what appears as cometary activity over a period of 8 months. However, while main belt comets best explained by ice sublimation are found in the outskirts of the main belt, where water ice is believed to be able to survive buried in moderately large objects for the age of the solar system deeply, the presence of volatiles in an object smaller than 300 m in radius would be very surprising in the inner asteroid belt.

A criterion to classify asteroids and comets based on the orbital parameters

The classification criterion between asteroids and comets has evolved in recent decades, but the main distinction remains unchanged. Comets present gas and dust ejection from the surface at some point of their orbits, therefore, these objects are considered to be active. On the other hand, asteroids do not show any kind of large scale gas and dust ejection, they are inert. Nevertheless, this classification scheme is impractical when we have more than 500,000 asteroids already discovered. In addition, comets are not active all along their orbits. In order for a comet to display activity at present or in the recent past in the inner region of the Solar System (heliocentric distance <2AU), the cometary orbit must be unstable in the time scale on the order of ten thousands of years; otherwise, the object should have completely consumed its volatile component. Close encounters with the most massive planets is the only mechanism that could produce “macroscopic” instabilities on a short time scale. The macroscopic changes in the orbital elements can be detected in a numerical integration of the dynamical evolution of the object over a time scale of several thousand years. This procedure to identify asteroids in cometary-like orbits is also impractical because it would require months of computing time. Therefore, a classification scheme based on the orbital elements to identify the border cases between the asteroid and comet populations is urgently required.We present a criterion to classify asteroids and comets and to find the border case based on the Tisserand’s parameter, the Minimum Orbital Intersection Distance (MOID), and considering some information regarding the aphelion and perihelion distances. Objects in mean-motion are disregarded. After applying a filter to the sample of over half a million asteroids already discovered to select the precise orbits and to the sample of 487 short-period comets, we apply the proposed classification criterion. The resulting sample consists of ∼331 Asteroids in Cometary Orbits (ACOs). The ACOs are further classified in subclasses similar to the cometary classification. There are 436 Jupiter Family Comets and 203 ACOs of the Jupiter Family type. This new criterion is more strict that the criteria used by other authors to identify ACOs; nonetheless, with the new criterion we ensure that the ACOs have a chaotic dynamical evolution similar to the periodic comets. The discovered dormant or extinct comets seems, if they exist at all, to be a small fraction of the active comets.We also analyse the available photometric data of ACOs to identify possible large brightness variations. Among the sample of ACOs, there is only one object with brightness variations typical of an active comet: 174P/(60558) Echeclus. But this object has already been double classified as asteroid and comet.

Evolution of thermally pulsing asymptotic giant branch stars – III. Dust production at supersolar metallicities★

We extend the formalism presented in our recent calculations of dust ejecta from the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase, to the case of super-solar metallicity stars. The TP-AGB evolutionary models are computed with the COLIBRI code. We adopt our preferred scheme for dust growth. For M-giants, we neglect chemisputtering by H$_2$ molecules and, for C-stars we assume a homogeneous growth scheme which is primarily controlled by the carbon over oxygen excess. At super-solar metallicities, dust forms more efficiently and silicates tend to condense significantly closer to the photosphere (r~1.5 R$_*$) - and thus at higher temperatures and densities - than at solar and sub-solar metallicities (r~2-3 R$_*$). In such conditions, the hypothesis of thermal decoupling between gas and dust becomes questionable, while dust heating due to collisions plays an important role. The heating mechanism delays dust condensation to slightly outer regions in the circumstellar envelope. We find that the same mechanism is not significant at solar and sub-solar metallicities. The main dust products at super-solar metallicities are silicates. We calculate the total dust ejecta and dust-to-gas ejecta, for various values of the stellar initial masses and initial metallicities Z=0.04, 0.06. Merging these new calculations with those for lower metallicities it turns out that, contrary to what often assumed, the total dust-to-gas ejecta of intermediate-mass stars exhibit only a weak dependence on the initial metal content.

Evolution of thermally pulsing asymptotic giant branch stars – II. Dust production at varying metallicity

We present the dust ejecta of the new stellar models for the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase computed with the COLIBRI code. We use a formalism of dust growth coupled with a stationary wind for both M and C-stars. In the original version of this formalism, the most efficient destruction process of silicate dust in M-giants is chemisputtering by H2 molecules. For these stars we find that dust grains can only form at relatively large radial distances (r~5 R*), where they cannot be efficiently accelerated, in agreement with other investigations. In the light of recent laboratory results, we also consider the alternative case that the condensation temperature of silicates is determined only by the competition between growth and free evaporation processes (i.e. no chemisputtering). With this latter approach we obtain dust condensation temperatures that are significantly higher (up to Tcond~1400 K) than those found when chemisputtering is included (Tcond~900 K), and in better agreement with condensation experiments. As a consequence, silicate grains can remain stable in inner regions of the circumstellar envelopes (r~2 R*), where they can rapidly grow and can be efficiently accelerated. With this modification, our models nicely reproduce the observed trend between terminal velocities and mass loss rates of Galactic M-giants. For C-stars the formalism is based on the homogeneous growth scheme where the key role is played by the carbon over oxygen excess. The models reproduce fairly well the terminal velocities of Galactic stars and there is no need to invoke changes in the standard assumptions. At decreasing metallicity the carbon excess becomes more pronounced and the efficiency of dust formation increases. This trend could be in tension with recent observational evidence in favour of a decreasing efficiency, at decreasing metallicity.

The sources of the unusual dust jets seen in Comet 103P/Hartley 2

We show that the unusual behavior of dust jets seen embedded in the sunward coma of 103P/Hartley 2 originate in active regions migrating over the two lobes of the nucleus following the Sun. The slowly changing orientation of the jets and their rapid changes in brightness is due to the shape and local topography of the nucleus coupled with the complex spin state. The intermittent appearance of a second jet is due to periodic deviations in the direction of the ejection of dust from the small lobe of the nucleus. The release of dust into the structures is likely due to the sublimation of H2O. The jets are characterized by injection speeds from the nucleus of 50–210m/s, a radiation pressure parameter 0.08<β<1, and a particle life-time near 7h. Within the jets, the average particle size decreases and the injection speed increases with distance from the nucleus.

A SHORT-DURATION EVENT AS THE CAUSE OF DUST EJECTION FROM MAIN-BELT COMET P/2012 F5 (GIBBS)

We present observations and an interpretative model of the dust environment of Main-Belt Comet P/2010 F5 (Gibbs). The narrow dust trails observed can be interpreted unequivocally as an impulsive event that took place around 2011 July 1st with an uncertainty of $\pm$10 days, and a duration of less than a day, possibly of the order of a few hours. The best Monte Carlo dust model fits to the observed trail brightness imply ejection velocities in the range 8-10 cm s$^{-1}$ for particle sizes between 30 cm and 130 $\mu$m. This weak dependence of velocity on size contrasts with that expected from ice sublimation, and agrees with that found recently for (596) Scheila, a likely impacted asteroid. The particles seen in the trail are found to follow a power-law size distribution of index $\approx$-3.7. Assuming that the slowest particles were ejected at the escape velocity of the nucleus, its size is constrained to about 200-300 m in diameter. The total ejected dust mass is $\gtrsim 5\times 10^8$ kg, with represents approximately 4 to 20% of the nucleus mass.

COMET 22P/KOPFF: DUST ENVIRONMENT AND GRAIN EJECTION ANISOTROPY FROM VISIBLE AND INFRARED OBSERVATIONS

We present optical observations and Monte Carlo models of the dust coma, tail, and trail structures of comet 22P/Kopff during the 2002 and 2009 apparitions. Dust loss rates, ejection velocities, and power-law size distribution functions are derived as functions of the heliocentric distance using pre- and post-perihelion imaging observations during both apparitions. The 2009 post-perihelion images can be accurately fitted by an isotropic ejection model. On the other hand, strong dust ejection anisotropies are required to fit the near-coma regions at large heliocentric distances (both inbound at $r_h$=2.5 AU and outbound at $r_h$=2.6 AU) for the 2002 apparition. These asymmetries are compatible with a scenario where dust ejection is mostly seasonally-driven, coming mainly from regions near subsolar latitudes at far heliocentric distances inbound and outbound. At intermediate to near-perihelion heliocentric distances, the outgassing would affect much more extended latitude regions, the emission becoming almost isotropic near perihelion. We derived a maximum dust production rate of 260 kg s$^{-1}$ at perihelion, and an averaged production rate over one orbit of 40 kg s$^{-1}$. An enhanced emission rate, accompanied also by a large ejection velocity, is predicted at $r_h>$2.5 pre-perihelion. The model has also been extended to the thermal infrared in order to be applied to available trail observations with IRAS and ISO spacecrafts of this comet. The modeled trail intensities are in good agreement with those observations, which is remarkable taking into account that those data are sensitive to dust ejection patterns corresponding to several orbits before the 2002 and 2009 apparitions.

Investigation of dust and water ice in comet 9P/Tempel 1 fromSpitzerobservations of the Deep Impact event

Context. The Spitzer spacecraft monitored the Deep Impact event on 2005 July 4 providing unique infrared spectrophotometric data that enabled exploration of comet 9P/Tempel 1’s activity and coma properties prior to and after the collision of the impactor. Aims. The time series of spectra take with the Spitzer Infrared Spectrograph (IRS) show fluorescence emission of the H2O ν2 band at 6.4 μm superimposed on the dust thermal continuum. These data provide constraints on the properties of the dust ejecta cloud (dust size distribution, velocity, and mass), as well as on the water component (origin and mass). Our goal is to determine the dust-to-ice ratio of the material ejected from the impact site. Methods. The temporal evolution of the continuum was analyzed using a dust thermal model which considers amorphous carbon and intimate silicate-carbon mixtures. The water emission was extracted from the spectra and the water columns within the Spitzer extraction aperture were inferred using a fluorescence excitation model. Time-dependent models simulating the development of the ejecta cloud and the sublimation of icy grains were developed to interpret the temporal evolution of both dust and water emissions within the field of view. Results. Both the color temperature of the grains in the ejecta cloud (375 ± 5 K) and their size distribution show that a large quantity of submicron grains were ejected by the impact. The velocity of the smallest grains is 230 m s −1 , with a power index for the size dependence of 0.3−0.5, in agreement with gas loading. The total mass of dust is (0.7−1.2) × 10 5 kg for grain sizes 0.1−1 μ ma nd (0.5−2.1) × 10 6 kg for sizes 0.1−100 μm. A sustained production of water is observed, which can be explained by the sublimation of pure ice grains with sizes less than 1 μm and comprising a mass of ice of (0.8−1.8) × 10 7 kg. The contribution of dirty ice grains to the ice budget is negligible. Assuming that water was essentially produced by icy grains present in the ejecta cloud, our measurements suggest a very high ice-to-dust ratio of about 10 in the excavated material, which greatly exceeds the gas-to-dust production rate ratio of ∼0.5 measured for the background coma. Alternately, if a large amount of material felt back to the surface and sublimated, ice-to-dust ratios of 1−3 are not excluded. A better understanding of the cratering event on 9P/Tempel 1 is required to disentangle between the two hypotheses. Evidence for grain fragmentation in the ejecta cloud is found in the data. The pre-impact water production rate is measured to be (4.7 ± 0.7) × 10 27 mol s −1 .

On the possible ejection of meteoroids from asteroid (3200) Phaethon in 2009

Asteroid (3200) Phaethon is the supposed parent body for the Geminid meteoroid stream and previously it has never shown any trace of activity. However, it doubled its brightness unexpectedly and sharply in 2009 June. This short outburst could imply that an ejection of dust particles had taken place. We have modelled this dust ejection and the subsequent evolution of the meteoroid swarm, with the aim of determining whether the dust could be observed as meteors on Earth in the near future. We also wish to determine whether the outburst activity can be distinguished from the activity of the main shower. We have found that the model dust swarm is slowly approaching Earth and that it will enter the Earth’s influence sphere (<0.03 au) in 2014. The minimum distance between particles and the Earth will be at least 0.015 au until 2050. Therefore, it will be possible to observe the resulting meteors, but the probability of the event is small. The outburst in the Geminid’s activity as a result of this swarm might take place at λ ⊙ = 262°.5 (i.e. after the main Geminid’s maximum). To exceed the usual level of activity, the mass of the 2009 swarm should exceed ∼10 8 kg. The radiation area of the model outburst meteors is a small spot: α≈ 114°.65 ± 2°.5, δ≈ 32°.7 ± 0°.1.

DRAMATIC INFRARED VARIABILITY OF WISE J1810-3305: CATCHING EARLY-TIME DUST EJECTION DURING THE THERMAL PULSE OF AN ASYMPTOTIC GIANT BRANCH STAR?

We present the discovery of a source with broadband infrared photometric characteristics similar to Sakurai's Object. WISE J180956.27-330500.2 (hereafter, J1810-3305) shows very red WISE colors, but a very blue 2MASS [K] vs. WISE [W1 (3.4 micron)] color. It was not visible during the IRAS era, but now has a 12 micron flux well above the IRAS point source catalog detection limit. There are also indications of variability in historical optical photographic plates, as well as in multi-epoch AKARI mid-infrared measurements. The broadband infrared spectral energy distribution, post-IRAS brightening and multiwavelength variability are all characteristics also shared by Sakurai's Object - a post asymptotic giant branch (post-AGB) star which underwent a late thermal pulse and recently ejected massive envelopes of dust that are currently expanding and cooling. Optical progenitor colors suggest that J1810-3305 may have been of late spectral class. Its dramatic infrared brightening, and the detection of a late-type optical counterpart are consistent with a scenario in which we have caught an extremely massive dust ejection event (in 1998 or shortly before) during the thermal pulse of an AGB star, thus providing a unique opportunity to observe stellar evolution in this phase. J1810-3305 is the only source in the entire WISE preliminary data release with similar infrared SED and variability, emphasizing the rarity of such sources. Confirmation of its nature is of great importance.

Local and Global Environmental Effects of Impacts on Earth

Research Article| February 01, 2012 Local and Global Environmental Effects of Impacts on Earth Elisabetta Pierazzo; Elisabetta Pierazzo 1Planetary Science Institute1700 E. Fort Lowell Rd, Suite 106, Tucson, AZ, USA †Author deceased Search for other works by this author on: GSW Google Scholar Natalia Artemieva Natalia Artemieva 1Planetary Science Institute1700 E. Fort Lowell Rd, Suite 106, Tucson, AZ, USA2Institute for Dynamics of Geospheres, Russian Academy of ScienceLeninsky pr. 38, bldg.1, Moscow 119334, RussiaE-mail: artemeva@psi.edu Search for other works by this author on: GSW Google Scholar Author and Article Information Elisabetta Pierazzo †Author deceased 1Planetary Science Institute1700 E. Fort Lowell Rd, Suite 106, Tucson, AZ, USA Natalia Artemieva 1Planetary Science Institute1700 E. Fort Lowell Rd, Suite 106, Tucson, AZ, USA2Institute for Dynamics of Geospheres, Russian Academy of ScienceLeninsky pr. 38, bldg.1, Moscow 119334, RussiaE-mail: artemeva@psi.edu Publisher: Mineralogical Society of America First Online: 09 Mar 2017 Online ISSN: 1811-5217 Print ISSN: 1811-5209 © 2012 by the Mineralogical Society of America Elements (2012) 8 (1): 55–60. https://doi.org/10.2113/gselements.8.1.55 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Elisabetta Pierazzo, Natalia Artemieva; Local and Global Environmental Effects of Impacts on Earth. Elements 2012;; 8 (1): 55–60. doi: https://doi.org/10.2113/gselements.8.1.55 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract The environmental effects of impact events differ with respect to time (seconds to decades) and spatial (local to global) scales. Short-term localized damage is produced by thermal radiation, blast-wave propagation in the atmosphere, crater excavation, earthquakes, and tsunami. Global and long-term effects are related to the ejection of dust and climate-active gases (carbon dioxide, sulfur oxides, water vapor, methane) into the atmosphere. At the end of the Cretaceous, the impact of a >10 km diameter asteroid led to a major mass extinction. Modern civilization is vulnerable to even relatively small impacts, which may occur in the near future, that is, tens to hundreds of years. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

P/2010 A2 LINEAR

Comet P/2010 A2 LINEAR is an object on an asteroidal orbit within the inner main belt, therefore a good candidate for membership with the main belt comet family. It was observed with several telescopes (ESO New Technology Telescope, La Silla, Chile; Gemini North, Mauna Kea, Hawaii; University of Hawaii 2.2 m, Mauna Kea, Hawaii) from 14 Jan. until 19 Feb. 2010 in order to characterize and monitor it and its very unusual dust tail, which appears almost fully detached from the nucleus; the head of the tail includes two narrow arcs forming a cross. No evolution was observed during the span of the observations. Observations obtained during the Earth orbital plane crossing allowed an examination of the out-of-plane 3D structure of the tail. The immediate surroundings of the nucleus were found dust-free, which allowed an estimate of the nucleus radius of 80–90 m, assuming an albedo p = 0.11 and a phase correction with G = 0.15 (values typical for S-type asteroids). A model of the thermal evolution indicates that such a small nucleus could not maintain any ice content for more than a few million years on its current orbit, ruling out ice sublimation dust ejection mechanism. Rotational spin-up and electrostatic dust levitations were also rejected, leaving an impact with a smaller body as the favoured hypothesis. This is further supported by the analysis of the tail structure. Finston-Probstein dynamical dust modelling indicates the tail was produced by a single burst of dust emission. More advanced models (described in detail in a companion paper), independently indicate that this burst populated a hollow cone with a half-opening angle α ~ 40° and with an ejection velocity vmax ~ 0.2 m s-1, where the small dust grains fill the observed tail, while the arcs are foreshortened sections of the burst cone. The dust grains in the tail are measured to have radii between a = 1–20 mm, with a differential size distribution proportional to a−3.44 ± 0.08. The dust contained in the tail is estimated to at least 8 × 108 kg, which would form a sphere of 40 m radius (with a density ρ = 3000 kg m-3 and an albedo p = 0.11 typical of S-type asteroids). Analysing these results in the framework of crater physics, we conclude that a gravity-controlled crater would have grown up to ~100 m radius, i.e. comparable to the size of the body. The non-disruption of the body suggest this was an oblique impact.