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Topic: Ejecta

In the News (Fri 17 Feb 12)

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	Rays & Ejecta
		Much of this is banked into the familiar circular wall, whilst most of the rest of the ejecta - the material thrown out by the impact - is generally deposited as bright rays radiating from the impact site.
		In large impacts, some of the ejecta can be thrown out at more than the Moon's escape velocity.
		Fragments of this have eventually reached the Earth, to fall as meteorites.
	www.inconstantmoon.com /not_rays.htm (116 words)

	ceous-Tertiary Boundary Stratigraphy near San Antonio,
		The diamictite is a direct ejecta deposit, itself 14-m thick, comprised of debris ranging from clay-size to 8-m diameter boulders.
		Bedding in Belizan ejecta diamictite is particularly interesting because it suggests that different parts of the ejecta flow were moving at slightly different speeds or took slightly different flow paths.
		In the foothills of the Maya Mountains, and in the Cayo District of central Belize near Belmopan, the capital of Belize, a sedimentary layer approximately 30 m thick comprises the Cretaceous-Tertiary (KT) boundary.
	www.auburn.edu /~kingdat/kt_boundary_page.htm (9533 words)

	Deep Impact Ejecta Plume Behavior
		As part of the Deep Impact Discovery mission, the purpose of this project is to investigate the possibility of determining the mass of a target comet by monitoring the expansion and behavior of an impact ejecta plume emanating from that target comet.
		Below are two simulation animations, showing the ejecta plume behavior which results from a Deep Impact like collision on a triaxial-ellipsoid body of density 1.5 g/cc and having a 6 km long major axis and 3 km long minor axis (about the size of comet Tempel 1).
		Two different cratering regimes are depicted: a "gravity-domimated" cratering regime, where the comet material is inherently weak and the comet's gravity domimates the crater and ejecta plume formation process, and a "strength-dominated" cratering regime, where the comet material is strong enough to dominate the crater and ejecta plume formation process.
	www.astro.cornell.edu /~richardson/ejector.html (1509 words)

	Pto. Mínguez-Ejecta
		to be ejecta of the Azuara impact structure, they also pointed to the similarities of the Pelarda Fm.
		These grand outcrops, which prove to be one of the most attractive impact ejecta deposits worldwide, are now considered to probably not expose ejecta from the Azuara structure because of their thickness with relation to distance.
		Instead, the Rubielos de la Cérida companion impact structure is suggested to be the source of the ejecta.
	www.impact-structures.com /spain/ptominguez.htm (321 words)

	[48.09] Cassini Impact Basin (Mars) Ejecta Deposits Revealed by MOC and MOLA Data
		Preliminary geologic mapping of Cassini delineated ejecta deposits to the west and south of the basin's rim [1].
		In order to sample the geomorphic characteristics of the ejecta unit for Cassini, an area of one basin radius from the rim was investigated.
		This study only considers ejecta deposits situated to the west and south of the basin rim due to the superposition of Luzin crater and its deposits on the northern rim of Cassini.
	www.aas.org /publications/baas/v33n3/dps2001/125.htm (184 words)

	Ejecta Blanket - Museum fuer Naturkunde Berlin (Site not responding. Last check: )
		The scope of this project is to map the ejecta blanket on the Yucatán Peninsula and to analyze its sedimentological and petrographical characteristics.
		Continuous ejecta blankets are forming shortly after the impact of an asteroid or comet by the ballistic ejection and secondary redeposition of crater material around the final impact crater.
		Because the larger geological formations on the moon are formed by ejecta material, the formation processes of ejecta blankets were essential for the understanding of the geology of the moon and the planning of the Apollo missions in the 70's (model of 'ballistic sedimentation', Oberbeck, 1975; Fig.
	www.museum.hu-berlin.de /min/forsch/forschprojects/impact/ejekta.asp?lang=1 (2198 words)

	The Real Ejecta of Endurance Crater? Discussion - Mars Rover Blog
		The material above the ejecta is a later impact surge deposit that covered Meridiani, filling all smaller craters and adding a few meters of new material to the surface of the plains.
		The initial thermal deterioration of the icy conglomerates would tend to reduce the ejecta pile to a smoother surface quite effectively, but the material that had been transformed to sulphate before the impact would not be affected and end up standing high.
		Near the crater is a jumble of bedded ejecta that have been eroded flat and show bedding surfaces exposed at various angles.
	www.marsroverblog.com /discuss-39271-the-real-ejecta-of-endurance-crater.html (1997 words)

	Pyroclastic Materials
		Fragments which are thrown out by volcanic explosions are referred to collectively as ejecta, and accumulations of these fragments are known as pyroclastic rocks or tephra depending on whether they are consolidated or not.
		Magmatic ejecta and Type I non-magmatic ejecta, which are derived from molten magma of the same eruption, are termed essential ejecta, and are typically partly or entirely glass (vitric).
		Some accessory ejecta consist of coarse-grained clots of several minerals that represent cognate material that was torn from the conduit walls or from parts of magma crystallized at depth.
	www.geo.ua.edu:16080 /volcanology/lecture_notes_files/pyroclastic_materials.html (1140 words)

	The Chicxulub Debate
		In l992 the first evidence of impact ejecta (glass spherule deposits) in NE Mexico was discovered at El Mimbral underlying a thick siliciclastic unit, which in turn underlies the KT boundary marked by an Ir anomaly and the first Danian species.
		The original spherule ejecta layer is 1.8 m thick and consists of almost pure impact spherule glass at the base and few clasts from the underlying sediments.
		The spherule ejecta (unit 1) at the base of the siliciclastic deposit, which is generally considered the direct ejacta fallout from the Chicxulub impact, represents two events separated by thousands of years during which limestones accumulated and invertebrates burrowed on the ocean floor.
	geoweb.princeton.edu /people/faculty/keller/chicxpage1.html (4859 words)

	Deep Impact Ejecta Plume Behavior (Site not responding. Last check: )
		As part of the Deep Impact Discovery mission, the purpose of this project is to investigate the possibility of determining the mass of a target comet by monitoring the expansion and behavior of an impact ejecta plume emanating from that target comet.
		Below are two simulation animations, showing the ejecta plume behavior which results from a Deep Impact like collision on a triaxial-ellipsoid body of density 1.5 g/cc and having a 6 km long major axis and 3 km long minor axis (about the size of comet Tempel 1).
		Two different cratering regimes are depicted: a "gravity-domimated" cratering regime, where the comet material is inherently weak and the comet's gravity domimates the crater and ejecta plume formation process, and a "strength-dominated" cratering regime, where the comet material is strong enough to dominate the crater and ejecta plume formation process.
	www.lpl.arizona.edu /~jrich/ejector.html (1520 words)

	Geology of Mars } Cratering
		Compared with the Moon and Mercury, ejecta blankets and fields of secondary craters are less prominent on Mars.
		Ejecta blankets of lunar craters are usually blocky near the rim and grade outward with increasingly more fine grain particles until the blanket merges with the surrounding area.
		The ejecta consist of several relatively thin sheets with tongue-shaped fronts.
	www.lukew.com /marsgeo/cratering2.html (292 words)

	International Space School Educational Trust ISSET
		Many scientists have speculated that the form of the ejecta blankets of medium-sized craters depends on the amount of subsurface water present when the impactor hit the surface.
		Certainly the ejecta resembles patterns that one might see throwing rocks into fluid mud, and for this reason these craters are often called "splosh" or "fluidized ejecta" craters.
		However, one must be careful not to predict the behavior of impactors moving at many kilometers per second from pebbles tossed into mud, and the question of exactly what factors contribute to the form of these ejecta patterns must wait for the further exploration of the planet.
	www.isset.org /doc.php?pagelocation=59&group=229&file=page2 (202 words)

	Pulsed-Power Experiments at the Pegasus II Facility
		At this interface, metallic ejecta can be injected into the gas, contributing to the mix of those materials with the gas, which in turn has an effect on the performance of the nuclear device.
		The actual hologram is made when the scattered light from the ejecta interferes with the unscattered laser light (reference beam) at the plane of the film.
		Ejecta data have been obtained for both aluminum and tin targets for which the target surface finish and shock strength have been varied.
	www.lanl.gov /orgs/p/p-22/liner.html (2262 words)

	Ida ejecta abstract (Site not responding. Last check: )
		Azzurra ejecta launched in the direction of rotation at speeds near 10 m/s are lofted over the asteroid and swept up onto the rotational leading surface on the opposite side.The landing locations of these particles closely match the distribution of large ejecta blocks observed in high resolution images of Ida (Lee et al., this issue).
		While little ejecta from Ida is captured by Dactyl, about half of the mass ejected from Dactyl at speeds of up to 20 m/s eventually falls on Ida. Particles launched at speeds just barely exceeding Dactyl's escape velocity can enter relatively long term orbit around Ida, but few are ultimately reaccreted by the satellite.
		As the smallest solar-system object yet imaged by a spacecraft, the morphology of Dactyl is an important clue to the asteroid population at the smallest sizes.
	www.boulder.swri.edu /%7Ebottke/Abstracts/ida_ejecta_abs.html (455 words)

	Cinder Cones
		The forms of craters are a function of the nature of explosive eruptions and the mechanical properties of ejecta.
		Ejecta that make up cinder cones are well stratified, with layers of different coarseness ranging from bombs to ash and consisting mostly of lapilli.
		Ejecta from violent eruptions diminish outward in thickness and size less rapidly than do the ejecta laid down by weak eruptions.
	www.geo.ua.edu:16080 /volcanology/lecture_notes_files/cinder_cones.html (474 words)

	Piezo Probes
		Ejecta is fine particulate matter that has a greater velocity than the parent plate.
		Evolution of this ejecta can be observed in the following results where the density of ejecta arising on seven piezo probes positioned (stood off) at a range of distances from the surface.The probes that are at the greater stand off see a shallower, longer ramp to their density histories.
		The ejecta is separating from the parent material due to it being at a higher velocity.
	www.awe.co.uk /main_site/scientific_and_technical/featured_areas/hydrodynamics_contents/esr-contents/esr-c/piezo_probes (339 words)

	Ejecta
		The typical PZ ejecta landforms are visualized as a pear-shaped, oval or elliptical landform, which sets above the surrounding landscape as a knoll, hill, or island.
		The underlying terrestrial landscape will influence the visualized ejecta shape, such that the stylized shape would be “broken” over terrain that was much rougher than the emplaced material thickness, or too steep to retain the ejecta intact.
		Nevertheless, we strongly suggest that the resulting PZ ejecta landforms are seen to retain the suggested geometry across the entire range of landform sizes, thereby facilitating the recognition of the ejecta using remote imaging techniques.
	perigeezero.org /treatise/Morphology/ejecta/index.html (1085 words)

	Europa Ice Clipper: Impactor and Plume Dynamics
		Ejecta is collected as the spacecraft passes through the ejecta plume.
		For a non-porous surface, such as annealed ice, cratering is in the strength- regime, and the total ejecta mass depends on the tensile strength of the target material.
		To determine the mass of ejecta collected by the spacecraft, the mass and velocity distributions of the ejecta at the flyby altitude of the spacecraft are required.
	www.astrobiology.com /europa/clipper/d41.impactor.html (1130 words)

	2001 Belize Expedition Objectives - What We Do \| The Planetary Society
		These expeditions brought back a wealth of data that is helping us to understand large impact processes and their possible implications in the evolution of life on our planets.
		To determine the extent of the ejecta material in Quintana Roo, Mexico and Northern and Central Belize.
		To measure the size of cobbles and pebbles in ejecta to determine the effect of atmospheric sorting during ballistic transport.
	www.planetary.org /programs/projects/near_earth_objects/neo_earth_expeditions/2001_objectives.html (449 words)

	The Role of Volatiles in Martian Oblique Impact Ejecta Emplacement (Site not responding. Last check: )
		The ejecta from oblique impacts in a dry vacuum follow a consistent pattern as the impact angle decreases.
		All of the ejecta in the dry-vacuum craters was emplaced ballistically and exhibits no post-emplacement flow.
		The similarity in ejecta patterns between the Martian rampart craters and the ballistically emplaced dry-vacuum craters suggests that Martian crater ejecta are first ballistically emplaced.
	www.gi.alaska.edu /~rherrick/reprints/2004AGUOblique.html (413 words)

	Columbia News ::: Columbia Astronomers Find First Supernova Remnant In The Making (Site not responding. Last check: )
		The activity was sighted on Dec. 25, 1999, by a team of Columbia astrophysicists, Stephen Lawrence, Arlin Crotts, Ben Sugerman, and Robert Uglesich, led by Patrice Bouchet of the National Optical Astronomy Observatories' Cerro Tololo Inter-American Observatory (CTIO).
		A "hot spot" that appeared in the circumstellar ring around the supernova in 1997 was believed to be the first impact of supernova ejecta, but no other activity sites had been observed until the CTIO and Columbia team sighted this one in December.
		This collision of supernova ejecta with the wind material, now forming the circumstellar shell, was predicted to occur sometime between 1995 and 2010.
	www.columbia.edu /cu/news/00/02/supernova.html (620 words)

	Volcanic and Geologic Terms
		Agglutinate: A pyroclastic deposit consisting of an accumulation of originally plastic ejecta and formed by the coherence of the fragments upon solidification.
		Each is relatively short, but collectively they form a linear zone in which the strike of the individual features is oblique to that of the zone as a whole.
		Ejecta: Material that is thrown out by a volcano, including pyroclastic material (tephra) and lava bombs.
	volcano.und.nodak.edu /vwdocs/glossary.html (4560 words)

	Mars Odyssey Mission THEMIS: Feature Image: Tooting Crater's Tangled Tale
		The Hawaii team notes that the ejecta pattern around the crater extends twice as far (about 50 km or 30 mi) to the northeast than to the southwest.
		These show that much of the southern ejecta layer is 3 to 5 m (10 to 16 ft) thick, while the rampart that marks its greatest extent rises 65 to 125 m (200 to 400 ft) high, being higher toward the north, west, and southeast.
		The difference may indicate the ejecta is loosely packed compared to the original layers and thus appears to bulk bigger than it is.
	themis.asu.edu /features/tooting (1007 words)

	High energy emission from supernovae interacting with the circumstellar medium (Site not responding. Last check: )
		The main goal of this project is to study the high energy emission originated by the interaction of the supernova ejecta with the circumstellar material (CSM) lost by the progenitor star during the last evolutionary stages that happen before explosion.
		From the properties (spectrum and light curve) of this emission, it is possible to reconstruct the mass loss history of the progenitor star, and the distribution and composition of the ejecta and CSM.
		The fluxes of the two spectral components provide also an estimate of the mass loss rate of the progenitor of SN 1995N, that turns out to be between 1.0E-6 and 1.0E-4 solar masses per year, value consistent with the expected mass loss rate from a red supergiant.
	www.pd.astro.it /oapd/2/2_1/2_1_5/2_1_5_2.html (343 words)

	U. S. Geological Survey research on the Wabar impact site, Saudi Arabia
		The crater complex and its associated ejecta field are largely contained within a 500 meter by 1,000 meter, roughly elliptical area located in the north-central core of the Ar-Rub' Al-Khali desert of Saudi Arabia, about 550 kilometers by air southeast of the capital Riyadh.
		Note the changing ratio of "Insta-Rock" ejecta (light color) to high-temperature glass slag ejecta (darker color); this asymmetry reflects both the shallow (probably 20-45 degrees from the horizontal), N60W arrival-direction of the asteroid, and the apparent from-the-southeast direction of the prevailing wind at the time of impact.
		In the dense ejecta field there is also fl, melted slag (we call this "glass") formed by admixture at the shock front of the impacting meteorite (7-10%) and the sand that it hit (90-93%).
	volcanoes.usgs.gov /jwynn/3wabar.html (1854 words)

	Ejecta - TheBestLinks.com - Crater, Volcano, TheBestLinks.com:Find or fix a stub, Magma, ...
		Ejecta, Crater, Volcano, TheBestLinks.com:Find or fix a stub, Magma...
		In volcanology, ejecta consists of particles that came out of a volcanic vent, traveled though the air or under water, and fell back on the ground surface or on the ocean floor.
		In planetary geology, ejecta can also refer to the debris that is ejected during the formation of an impact crater.
	www.thebestlinks.com /Ejecta.html (146 words)

	Martian Craters (Site not responding. Last check: )
		Many scientists have speculated that the form of the ejecta blankets of medium-sized craters depends on the amount of subsurface water present when the impactor hit the surface.
		Certainly the ejecta resembles patterns that one might see throwing rocks into fluid mud, and for this reason these craters are often called "splosh" or "fluidized ejecta" craters.
		However, one must be careful not to predict the behavior of impactors moving at many kilometers per second from pebbles tossed into mud, and the question of exactly what factors contribute to the form of these ejecta patterns must wait for the further exploration of the planet.
	cmex.ihmc.us /MarsEssy/crater.htm (335 words)

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