Parent crater for Australasian tektites beneath the sands of the Alashan Desert, Northwest China: Best candidate ever?

ABSTRACT Australasian tektites represent the largest group of tektites on Earth, and their strewn field covers up to one sixth of Earth’s surface. After several decades of fruitless quest for a parent crater for Australasian tektites, mostly in the main part of the strewn field in Indochina, the crater remains undiscovered. We elaborate upon a recently suggested original hypothesis for the impact in the Alashan Desert in Northwest China. Evidence from geochemical and isotopic compositions of potential source materials, gravity data, and geographic, paleoenvironmental, and ballistic considerations support a possible impact site in the Badain Jaran part of the Alashan Desert. In further support of an impact location in China, glassy microspherules recovered from Chinese loess may be the right age to relate to the Australasian tektite event, perhaps as part of the impacting body. The most serious shortcomings of the commonly accepted Indochina impact location include signs of little chemical weathering of source materials of Australasian tektites, unlike highly weathered sedimentary targets in Indochina, and questionable assumptions about transport of distal ejecta.

Improved Cleansing Process of Stuck Soil Brush from Cleaners during the Sugar Beet Harvest

Purpose of the present research is to improve the quality of cleaning sugar beetroot crops with a brush cleaner by developing a device for removing stuck soil. The article defines the dependence of the impact velocity on the distance to the place of impact, which changes linearly, increasing with increasing distance to the place of impact. Analysis of the dependence shows that the speed can be most significantly influenced by the speed of the conveyor and the radius of the trajectory of the end of the bending lint, which directly depends on the diameter of the cylindrical brush. Nomogram was obtained to determine the most optimal parameters of the impact site on the lint. When conducting studies with heavy loamy chernozem soils with a moisture content of ≈28%, it revealed that the minimum required brush lint impact velocity to separate soil from the coils of the spring is about ≈ 2.5 m/s. The analysis of the dependence shows that the most effective cleaning of the brush lint from the stuck soil (90-98%) occurs when a blow is applied at a distance of 40 to 78 mm from the place of attachment of the lint with a lint length of 100 mm. The impact velocity of the brush lint should be large enough to separate the soil of maximum stickiness from the coil of the spring, however, it should not be greater than the speed causing lint cutting, i.e. the speed at which the brush lint are destroyed.

The 2009 Wesley impact: Asteroidal or Cometary?

<p>We present Earth-based observations of Jupiter from 1994 and 2009, which respectively capture the effects on Jupiter’s atmosphere by the impacts of Comet D/Shoemaker-Levy 9 (SL9) and the impact by an unknown object whose visible impression on Jupiter’s appearance was discovered by Anthony Wesley.  Previous studies have suggested the 2009 impactor was by an asteroid on the basis of differences in Jupiter’s atmospheric response compared to the 1994 impact by SL9.  These differences include detections of 9.1-μm silicate features in the 2009 impact site (Orton et al., 2010, Icarus 211, 587-602) and the fact the 2009 debris field shrank faster (Hammel et al., 2010, ApJL 715, L150-L154), both of which suggest the 2009 impactor was more rocky/refractory in composition.  However, Schenk <em>et al.</em> 2004 (Jupiter: The Planet, Satellites and Magnetosphere, Bagenal, Dowling, McKinnon, 427-456) state that comets are orders of magnitude more likely to impact Jupiter than asteroids since Jupiter should have cleared its orbit a long time ago. Thus, either (1) the 2009 impact was caused by an asteroid and therefore a statistical fluke, (2) Jupiter-Family Comets (JFCs) are a highly heterogeneous population, with some containing rocky/refractory interiors hidden from remote-sensing, or (3) there is a population of asteroids among bodies classified as JFCs. In order to explore these hypotheses, we performed a comparative spectral re-analysis of broadband imaging and low-resolution spectra measured during/after the 1994 and 2009 impacts. The comparison used consistent procedures for reduction and calibration of the data, atmospheric models, radiative-transfer software and spectroscopic line data in order to facilitate direct comparisons between 1994 and 2009 events.  </p>

Mars surface dust activation at small meteoroid’s impacts

<p>We continue the analysis of HiRISE high resolution images of Mars to understand properties of dust covering the surface. The data on dust devils observed with Mars landers and surface traces of dust devils could be expanded with elongated albedo features imaged near “new” impact sites (“new” means that we have orbital images before and after the meteoroid impact, which give us an estimate of the impact date and the age of a feature). The age of these features is from 0.5 to 12 terrestrial years. From geometric reasons we could assume that the most possible mechanism of this elongated albedo details is the “footprint” of two or more colliding air shock waves, generated at the impact site. Of ~1200 “new” impacts known today, in 18 cases crater pairs or clusters, created with fragments of the same “parent” meteoroid, we recognize 24 thin “parabolas” with a width of 1 to 10 m (0.2 to 10 main crater diameters, <em>D</em>), extended to 100 – 400 m (3 to 100 <em>D</em>) from the impact site. In ~30 cases near a single crater we observe a curved albedo feature nick-named “scimitar”. These features have width, growing with a distance from the impact point. The length varies from 10 to 100 <em>D</em>, the width varies from 1 to 10 <em>D</em>. Our working hypothesis is that “scimitars” are footprints of ballistic and spherical air shock wave collision at the surface. Both “parabolas” and “scimitars” have an exact bilateral symmetry, which allows us to reconstruct the flight direction of projectiles.</p><p>We estimate the equivalent energy of spherical air blasts with two different assumptions for “parabolas” and “scimitars” formation. For parabolas we assume a mechanism, similar to dust devil track formation – the negative pressure excurse uplifts the upper fine dust layer. The main assumption is that the dark parabolic strip width corresponds the wave length of the negative pressure phase in the air shock wave. It gives us the minimum energy estimate as in reality the negative phase could be longer. The negative pressures here along the parabola length decay from about 10 to 5 Pa with the phase duration of a few milliseconds. Such a suction pulse is able to mobilize dust particles 50 to 100 microns in size.</p><p>For scimitars, which in contrast to “dark” parabolas are typically “brighter” than surrounding area, we have no a good mechanical explanation of origin. However, with limits of our current model, the spherical “explosion” air blast should be enough energetic, to overrun the ballistic shock wave. From non-linear motion of the shock wave front we can estimate the fraction of meteoroid’s kinetic energy, converted to the air blast energy. The model is able to reproduce approximately the scimitar’s curvature.</p>