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Small Double Craters
Published in Gilbert Fielder, Secrets of the Moon, 2021
Although relatively few among the craters identified, possible impact craters are those circular craters that show sharp features such as an upturned rim that casts a thin crescent of shadow outside the crater as well as a relatively sharply defined internal shadow. I have referred to these as eumorphic craters. The largest are surrounded by bright haloes and, mapping them on the high resolution (H) coverage, we noticed that many were double, a smaller crater nesting (most frequently concentrically) within the larger one. These eumorphics are found in roughly equal numbers per unit area (see Table 22.1) on both of the flows f1 and f2. There is a strong possibility that many of them are impact craters.
Small Bodies: Asteroids and Meteoroids
Published in Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice, Solar System, 2021
Thomas Hockey, Jennifer Lynn Bartlett, Daniel C. Boice
If all these things dropping out of the sky are mostly harmless, what could create the terrifying scenario with which we opened this chapter? The surfaces of the other terrestrial planets are scarred by large impact craters. Yet, only in 1960 did American geologist Eugene Shoemaker7〈1928–1997〉 convincingly identify the first bone fide terrestrial impact crater: Barringer Crater; it is a 49,000-year-old crater in the dry, preserving highlands of Arizona (just off US Interstate 40). However, this particular hole in the ground is now 1.2 kilometers (0.75 miles) across and 170 meters (550 feet) deep. Geologists estimate that the impactor had a diameter of 'only' about 40 meters (130 feet). While impressive to human eyes, it is trivial compared to the scars visible on other worlds (Figure 9.7).
Discharge and electromagnetic radiation behind the hole of simulated charging satellite surface under impact
Published in Waves in Random and Complex Media, 2022
Enling Tang, Liangliang Zhao, Yafei Han, Chuang Chen, Mengzhou Chang
When the projectile hypervelocity impacts the target plate, the material of the projectile and the target plate melts, vaporizes and ionizes under the strong impact. The hot mixture of neutrals, ions and electrons in the impact crater has a high density in the initial moments, which is close to that of a solid material [38]. Because the impact plasma has the characteristics of high density in the initial stage, the probability of collision between the neutrals, ions and electrons in the plasma is very high, which may not meet the definition of standard plasma [39], which is usually called non-ideal plasma. The density gradient diffusing from high density to free interface drives the expansion of non ideal plasma, and the plasma reaches a dynamic equilibrium state. At this moment, the plasma is like the state of magnetic fluid, and its behavior is dominated by electrostatic forces. As the plasma continues to expand, the interaction force between particles can be ignored untimely. The plasma enters single particle motion stage, where the trajectory of each particle is independent and mainly influenced by the external electric field.
There is no geophysical evidence for the Mahuika Crater on the continental shelf southwest of New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2022
The existence of the Mahuika impact crater was proposed by Abbott et al. (2003) and subsequently fostered by Bryant et al. (2007). They describe a seafloor impact crater that is a >153 m deep depression with a width of 20.2 km (∼48.3°S, 166.4°E), at a depth of 300 m on the continental shelf near the Snares Islands/Tini Heke and Stewart Island/Rakiura, southwestern New Zealand. Abbott et al. (2003) describe the Mahuika Crater to be the result of the impact from comet X/1491 B1 (formerly 1491 II) (Hasegawa 1979), which allegedly generated a megatsunami in the late fifteenth century AD (Abbott et al. 2003; Bryant et al. 2007). The physical evidence, in its entirety, put forward by Abbott et al. (2003) for Mahuika Crater entailed the orientation of coast landforms along the eastern Australian coast suggested a tsunami wave originating from a locality of the crater; the sub-surface depth of impact deposits around the crater site; and the distribution of tektites in the marine sediments nearby.
Meteorite crater re-interpreted as iceberg pit in west-central Sweden
Published in GFF, 2021
Christian Öhrling, Henrik Mikko, Gustaf Peterson Becher, Carl Regnéll
During a geomorphological mapping project in Härjedalen, we recognized numerous landforms which we interpret as iceberg pits and plough marks formed in early Holocene glacial lakes. In this study, we focus on the depression at Torbygget and suggest that it is an iceberg-scouring mark, not a meteorite-impact crater.