Impact events

Initiating Event Feed Shuts Off Reactor Dump Works Accident Sequence Number Frequency (events/yr) Consequence (impacts/event)... 

The sizes and shapes of impact craters are easily measured at leisure after the impact event. The particles of a debris cloud can present more of a problem, however, because of the difficulty of recovering the particles without damaging them during the recovery process. Attempts at soft recovery have been numerous and of varying degress of success. Occasionally, it has been desir-... 

Keller, G. (1986) Stepwise mass extinction and impact events Late Eocene to early Oligocene. Marine Micropaleontology, 10, 267-293. 

Gyr ago. There is evidence that it was reheated as a result of a shock event about 4 Gyr ago and water flowed through it, depositing carbonate globules. It was ejected form the Martian surface by another impact event and orbited the Sun on its own for about 16 million years before intersecting the Earth s orbit and landing some 13000 years ago, impacting into the ice of Antarctica where it was found. 

By employing a laser for the photoionization (not to be confused with laser desorption/ ionization, where a laser is irradiating a surface, see Section 2.1.21) both sensitivity and selectivity are considerably enhanced. In 1970 the first mass spectrometric analysis of laser photoionized molecular species, namely H2, was performed [54]. Two years later selective two-step photoionization was used to ionize mbidium [55]. Multiphoton ionization mass spectrometry (MPI-MS) was demonstrated in the late 1970s [56—58]. The combination of tunable lasers and MS into a multidimensional analysis tool proved to be a very useful way to investigate excitation and dissociation processes, as well as to obtain mass spectrometric data [59-62]. Because of the pulsed nature of most MPI sources TOF analyzers are preferred, but in combination with continuous wave lasers quadrupole analyzers have been utilized [63]. MPI is performed on species already in the gas phase. The analyte delivery system depends on the application and can be, for example, a GC interface, thermal evaporation from a surface, secondary neutrals from a particle impact event (see Section 2.1.18), or molecular beams that are introduced through a spray interface. There is a multitude of different source geometries. 

We also have over 120 lunar meteorites in our collections. Because the Moon has no atmosphere, the irradiation history of these meteorites can include an extended period in the lunar regolith. The transit times from the Moon to the Earth range from a few x 104 years to nearly 10 Myr. Detailed analysis of exposure ages and terrestrial ages indicate that at least three impact events in the lunar highlands and five events in the lunar mare ejected the meteorites that have been recovered to date. 

What is the evidence that Martian meteorites came to Earth as a result of a few discrete impact events on the Martian surface ... 

Westphal, A. J., Snead, C., Butterworth, A. et al. (2004) Aerogel keystones extraction of complete hypervelocity impact events from aerogel collectors. Meteoritics and Planetary Science, 39, 1375-1386. 

The interaction of keV particles with solids has been characterized by the measurement of the angle and energy distribution of sputtered secondary ions and neutrals. The results are compared to classical dynamics calculations of the ion impact event. Examples using secondary ions are given for clean Ni 001), Cu 001) reacted with 0>, Ni 001 and Ni 7 9 11 reacted with CO, and Agllll) reacted with benzene. The neutral Rh atoms desorbed from Rh 001 are characterized by multiphoton resonance ionizaton of these atoms after they have left the surface. 

Take the case where a photocount is observed in the detector wall ("yes"), the quantum state is now of the form 3 — 7 and associates with a label state A. = —1). Store the quantum state by collecting the position of the impact event save the data set. If no-photocount is detected, the impact position of datum is stored with label A = +1), indicating that this event is associated with state 3 + 7). This process corresponds to "distillation" of quantum states into two exclusive data sets that can now be independently displayed. 

Silver, L. T. U-Th-Pb Isotope systems in Apollo 11 and 12 regolithic materials and a possible age for the Copernicus impact event. Paper presented at Amer. Geo-phys. Union 52nd Ann. Meeting. Washington, D. C. 1971. 

Cosmic-ray exposure ages are between —5.5 Ma and 7 Ma for all acapulcoites and most of the lodranites, possibly indicating sampling from a single impact event on a common parent body (McCoy et al., 1996, 1997a,b). 

For some asteroids, near-catastrophic impacts played an important role in their early geological evolution. Impact events ranging from local melting of the target area to complete disruption of the parent body are recorded in most groups of meteorites (Keil et al., 1994). Major impacts in the early solar system caused remixing of metal and silicate and large-scale redistribution of cold and hot material in the interior of some of the parent bodies. These processes had profound... 

Most lunar meteorites contain detectable concentrations of cosmogenic nuclides attributable to irradiation within a few meters of the lunar surface. This observation sets lunar meteorites apart from the general run of meteorites in which the signs of parent-body irradiation are rarer and generally harder to detect. The nearsurface irradiations prior to launch also hint at the importance of smaller impact events in launching lunar meteorites. We will return to the meaning of smaller below. 

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