Dating planetary surfaces Free webcamxxx for blackberry
The authors tested dating by counting small craters in a variety of presumed “old” and “young” regions of the moon, and got widely divergent results despite using standard methods and software.They urged a high degree of caution, therefore, when trying to infer the age of a planetary surface. Terrestrial planets have hard surfaces that can be re-shaped by several different processes: impact cratering, volcanism, erosion, and tectonics. Links to external sites will be displayed in another window.Next to it rests a dark sliver of 2.8-billion-year-old lava from the Moon.Anderson, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, picks up his favourite, a 1-gram slice of rock that cost him US0.Secondary craters are formed by fallback debris from large impacts (primary craters).A single large impact can produce a million secondary craters, blurring relationships between crater counts and the age of a surface.
The kinetic energy of the impacting meteorite or asteroid is converted into heat, sound, and mechanical energy---the projectile explodes on impact.
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There are still small chunks of rock orbiting the Sun left over from the formation of the solar system.
Astronomers had hoped that secondaries could be identified, thereby alleviating the confusion.
Not so; a new paper in indicates that many secondaries are very difficult to distinguish from primaries, because debris lofted up may go into orbit for years, falling down far away from the initial impact (distant secondaries).
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"But large impacts also have the ability to wipe out life forms, as evident from Earth’s dinosaur-killing Chicxulub impact 65 million years ago." Scientists also use craters to help date planetary surfaces, reasoning that the more craters pepper a region, the older it must be.