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Title: Nanoindenting the Chelyabinsk meteorite to learn about impact deflection effects in asteroids
Author: Carles E. Moyano-Cambero, Eva Pellicer, Josep M. Trigo-Rodríguez, Iwan P. Williams, Jürgen Blum, Patrick Michel, Michael Küppers, Marina Martínez-Jiménez, Ivan Lloro, Jordi Sort

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids. Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young's modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and, therefore higher values imply more efficient impacts. In the Chelyabinsk meteorite, the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and, therefore, increase the momentum multiplication. These results are relevant considering the growing interest in missions to test asteroid deflection, such as the recent collaboration between the European Space Agency and NASA, known as the Asteroid Impact and Deflection Assessment mission.

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RE: Chelyabinsk Meteors
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Cosmic collision created the Chelyabinsk meteor

Previous studies have identified filled-in cracks running through the rock, known as shock veins, produced by high temperature and pressure conditions. They suggest that Chelyabinsk experienced a large impact in its past.
Shin Ozawa of Tohoku University in Sendai, Japan and his colleagues examined some of the recovered fragments and found a particular form of the mineral jadeite that seems to have been formed by rapid crystallisation. This would require pressures of between 3 and 12 gigapascals and temperatures of 1700-2000 ºC. From that, they could calculate properties of the impacting body - it was likely to have been between 150 and 190 metres wide and travelling at anything from 1400 to 5400 kilometres an hour.

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Title: Chelyabinsk meteorite explains unusual spectral properties of Baptistina Asteroid Family
Author: Vishnu Reddy, Juan Sanchez, William Bottke, Ed Cloutis, Matt Izawa, Dave O'Brien, Paul Mann, Matt Cuddy, Lucille Le Corre, Michael Gaffey, Gary Fujihara

We investigated the spectral and compositional properties of Chelyabinsk meteorite to identify its possible parent body in the main asteroid belt. Our analysis shows that the meteorite contains two spectrally distinct but compositionally indistinguishable components of LL5 chondrite and shock blackened/impact melt material. Our X-ray diffraction analysis confirms that the two lithologies of the Chelyabinsk meteorite are extremely similar in modal mineralogy. The meteorite is compositionally similar to LL chondrite and its most probable parent asteroid in the main belt is a member of the Flora family. Intimate mixture of LL5 chondrite and shock blackened/impact melt material from Chelyabinsk provides a spectral match with (8) Flora, the largest asteroid in the Flora family. The Baptistina family and Flora family overlap each other in dynamical space. Mineralogical analysis of (298) Baptistina and 9 small family members shows that their surface compositions are similar to LL chondrites, although their absorption bands are subdued and albedos lower when compared to typical S-type asteroids. A range of intimate mixtures of LL5 chondrite and shock blackened/impact melt material from Chelyabinsk provides spectral matches for all these BAF members. We suggest that the presence of a significant shock/impact melt component in the surface regolith of BAF members could be the cause of lower albedo and subdued absorption bands. The parent asteroid of BAF was either a member of the Flora family or had the same basic composition as the Floras (LL Chondrite). The shock pressures produced during the impact event generated enough impact melt or shock blackening to alter the spectral properties of BAF, but keep the BAF composition largely unchanged.

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The Chelyabinsk meteor was a near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC), with an estimated speed of 18.6 km/s (over 41,000 mph or 66,960 km/h), almost 60 times the speed of sound
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Divers working at a Russian lake have recovered what may be a 570kg chunk of the space rock that exploded over Chelyabinsk earlier this year.
The object is thought to have plunged into Lake Chebarkul in central Russia leaving a 6m-wide hole in the ice.

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Meteor had other near-misses before exploding over Russia in February

The meteor that exploded over Chelyabinsk, Russia, in February likely had a near miss before it hit Earth, possibly with another solar system object or a too-close graze by the sun, scientists have found.
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NASA's Suomi (NPP) Satellite Detects A Plume From A Meteor

Some of the surviving pieces of the Chelyabinsk meteor (or bolide) fell to the ground near Chebarkul, Russia. But the explosion also injected hundreds of tons of dust into the stratosphere, allowing a NASA-NOAA satellite to make unprecedented measurements of a thin but cohesive and persistent dust belt.



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New Silver Coin Remembers the Chelyabinsk Meteorite

Now, a unique coin issued by the Cook Islands allows the viewer to relive this dramatic event.
The reverse design of the coin depicts how the affected people must have witnessed this unique event on that morning: The viewer looks through a shattered window and sees the meteorite blazing across the sky. As a special feature, each coin contains a small element made from a fragment of the meteorite itself. This is surrounded by a colored streak of flame running from the left to right.



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Astronomers identify 20 asteroids on similar path to Russian meteor

The house-sized rock that exploded spectacularly in the skies near Chelyabinsk, Russia, in February may have been a member of a gang of asteroids that still poses a threat to Earth, a new study says. The evidence is circumstantial, but future observations could help to settle the question.
The best sibling candidate, for instance, is a 200-metre-wide asteroid known as 2011 EO40, whose orbit was calculated from observations taken over just 34 days. That is too short a time to be able to pinpoint its position in the future, says Jon Giorgini, a senior analyst in the Solar System Dynamics Group at NASA's Jet Propulsion Laboratory in Pasadena, California. For that, researchers would need observations taken over the asteroid's two-year orbit, he says.

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Russian Meteor Explosion's Dust Cloud Lingered In Atmosphere for Months

When a meteor exploded over the Russian city of Chelyabinsk in February, pieces of the bus-sized space rock hit the ground while its detonation shattered windows, set off car alarms and injured more than 1,000 people.
Masked in the chaos, however, was an enormous plume of dust that the Russian meteor left behind in Earth's atmosphere. This cloud, which had hundreds of tons of material in it, was still lingering three months after the Feb. 15 explosion, a new study has found.

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