نتایج جستجو برای: crater defect
تعداد نتایج: 99333 فیلتر نتایج به سال:
[1] New spacecraft observations in the Nili Fossae region of Mars reveal two valley networks (!80 and !200 km long) that each formed distributary fans as they entered an ancient 40-km diameter impact crater. An outlet channel on the eastern crater rim, lying at an elevation above the fans, suggests these fans formed as subaqueous deltas in a crater lake. Water flowing in the valley networks ent...
Cross-basin winds produced by asymmetric insolation of the crater sidewalls occur in Arizona’s Meteor Crater on days with weak background winds. The diurnal cycle of the cross-basin winds is analyzed together with radiation, temperature, and pressure measurements at the crater sidewalls for a 1-month period. The asymmetric irradiation causes horizontal temperature and pressure gradients across ...
[1] We report on numerical modeling results of postimpact cooling of craters with diameters of 30, 100, and 180 km in an early Martian environment, with and without the presence of water. The effects of several variables, such as ground permeability and the presence of a crater lake, were tested. Host rock permeability is the main factor affecting fluid circulation and lifetimes of hydrothermal...
A method of improving coating thickness measurement repeatability of the ball crater method is proposed. The improvement is realized by using image processing techniques to measure the radii of crater circles from a microscope image. While traditional methods use a limited number of operator-selected points on a circle edge to calculate the radius value, the new method measures the radius by fi...
[1] Although diverse measurements have indicated H, OH , or H2O species in the lunar polar regions, pinpointing its location, form, and abundance in specific reservoirs has proven elusive. Here we report on the first orbital radar measurements of Shackleton crater near the lunar south pole. Mini-RF observations indicate a patchy, heterogeneous enhancement in CPR (circular polarization ratio) on...
Introduction. Crater densities have been instrumental in determining ages of surfaces on Mars and other cratered planetary bodies. Fundamental to this technique is the cumulative bombardment of the surface by projectiles supplied from the population of Mars-crossing asteroids and comets. Diameters of craters are a function of impact energy determined by the velocity and mass of the projectiles ...
The Ries Crater was formed about 12 million years ago, 120 km northwest of Munich in the district of Donau-Ries. The crater is estimated to have had a diameter of approximately 24 kilometers. In this report we discuss the preand post-impact structure of the crater site, and in particular try to investigate whether or not the Ries Crater shows evidence of structural uplift, a characteristic of m...
The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake bas...
Haldatie Is a 40 km multi-ringed crater that occurs along with similar structures in a belt within the Smylhii Basin, It is the best developed structurally of all ciraters in this belt and displays examples of all materials units of Mare Smythii. In addition to the outer rim, the crater displays a sharp-crested, nearly complete inner ring, and a complex central peak of round hills that are 3nO-...
Gravity data of Ceres returned by the National Aeronautics and Space Administration’s Dawn spacecraft is consistent with a lower density crust of variable thickness overlying a higher density mantle. Crustal thickness variations can affect the long-term, postimpact modification of impact craters on Ceres. Here we show that the unusual morphology of the 280 km diameter crater Kerwan may result f...
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