Results by Neukum et al. (2001) and Ivanov (2001) are combined with crater counts to estimate ages of Martian surfaces. These results are combined with studies of Martian meteorites (Nyquist et al., 2001) to establish a rough chronology of Martian history. High crater densities in some areas, together with the existence of a 4.5 Gyr rock from Mars (ALH84001), which was weathered at about 4.0 Gy...

Introduction: The Bosumtwi crater has a diameter of 10.5 km and is located in the center of Ghana in West Africa (6o 30’ N and 1o 25’ W). Its age is 1.05 Ma and it forms a well preserved impact structure with a well defined rim. Its center is occupied by the closed basin of Lake Bosumtwi. The target rock is essentially composed of Proterozoic (2.1 to 2.2 Ga) units of the Birimian Supergroup tha...

[1] Observations of fresh impact craters by the Opportunity rover and in high‐resolution orbital images constrain the latest phase of granule ripple migration at Meridiani Planum to have occurred between ∼50 ka and ∼200 ka. Opportunity explored the fresh Resolution crater cluster and Concepción crater that are superposed on and thus younger than the ripples. These fresh craters have small dark ...

525 © Meteoritical Society, 2001. Printed in USA. Abstract–It has been suggested that the formation of the 22 km diameter lunar crater Giordano Bruno was witnessed in June 1178 A.D. To date, this hypothesis has not been well tested. Such an impact on the Earth would be "civilization threatening". Previous studies have shown that the formation of Giordano Bruno would lead to the arrival of 10 mi...

Introduction: Impact events locally increase the temperature of a planetary crust, initiating hydrother-mal activity if water or ice is present. Impact-induced hydrothermal activity is responsible for mineralogical-ly and morphologically modifying many terrestrial craters [e.g., 1], and has been suggested for Martian craters [2, 3]. Present-day subsurface ice has been inferred at high latitudes...

[1] Crater statistics indicate alluvial fans, crater floor, and fill/mantling deposits within impact craters >50 km in diameter in southern Margaritifer Terra were likely emplaced during multiple epochs: fans formed during the Amazonian or near the Amazonian‐Hesperian boundary, crater floor deposits are likely Hesperian in age, and most fill/mantling deposits are Amazonian. The regional distrib...

A paraboloidal bow shock model is developed in order to estimate the surface distribution of gas shock-induced modifications surrounding Venusian impact craters. We apply two-dimensional oblique shock dynamics to describe a three-dimensional paraboloidal-shaped bow shock impinging upon an assumed incompressible Venusian surface. The effects of the hypersonic atmospheric shock acting on the Venu...

Several supporting observations indicate that Sithylemenkat Lake, Alaska; occupies a meteorite impact crater formed near the end of the Wisconsinan glaciation. The initial identification with Landsat imagery is attributed to the unique perspective provided by such imagery.

Introduction: The Ries of Nördlingen (diameter: 26 km, age: 14.35 Ma) is the type locality of suevite which is the most characteristic rock type formed in impact craters. Though studied since 1834 [1], the formation and emplacement of suevite in the Ries and in impact craters in general is still enigmatic. As information from suevite can contribute significantly with regard to understanding the...

Citizen science has become a popular tool for preliminary data processing tasks, such as identifying and counting Lunar impact craters in modern high-resolution imagery. However, use of such data requires that citizen science products are understandable and reliable. Contamination and missing data can reduce the usefulness of datasets so it is important that such effects are quantified. This pa...