Age dating crater counting
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.
The oldest terrestrial rocks, found in the Precambrian shield of Greenland, are about 3.8 billion years old. The youngest extensive stratigraphic units dated by isotopic methods are the mare basalts, which range in age from about 3.3 to 3.8 billion years.
Most of Earth's surface (the ocean basins) was formed by seafloor spreading during the last 200 million years (about the last 5 percent of geologic history). Rocks recovered from the lunar highlands are even older, and ages in excess of 4.3 billion years have been measured.
Crater counting is a method for estimating the age of a planet's surface.
The method is based upon the assumptions that a new surface forms with zero impact craters, and that impact craters accumulate at some constant rate.
In this sense, the derived age is a size-dependent Acrater retention [email protected] B the survival time of craters of given size.
It is not quite a formation age in the sense of the lava flow age, but conveys tremendous information about the erosion/deposition/resurfacing environment of Mars.
The accuracy of age estimates of geologically young surfaces based on crater counting on Mars has been questioned due to formation of large amounts of secondary craters.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 abstract states: The small crater populations (diameter smaller than 1 km) are widely used to date planetary surfaces.The reliability of small crater counts is tested by counting small craters at several young and old lunar surfaces, including Mare Nubium and craters Alphonsus, Tycho and Giordano Bruno.