Age dating crater counting blind dating 2016 deal
Ten kilometer diameter craters are produced on Earth at the rate of ~2 X 10 (Shoemaker et al., 1979).
From the calculated present cratering rates and the observed history of cratering in the Earth-Moon system, it can be shown that the period of early heavy bombardment probably ended 3.5 billion years ago on each of the terrestrial planets (Hartmann, 1972; Soderblom et al., 1974).
Accurate determinations of recent cratering rates on Earth are vital to the estimation of accurate absolute ages from crater densities on the terrestrial planets.
The Earth-Moon system also provides the essential record needed to determine the past variation of this cratering rate (Hartmann, 1972a).
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.
The isotopic method of determining absolute age is the most accurate and desirable way of dating planetary surfaces, but collecting and returning rock samples from distant planets and satellites is a difficult and expensive endeavor.
An assessment of mineral composition can be made from spectrophotometric observations, and plausible densities and masses can then be assigned to well-observed small bodies ().
If the cratering history is known for one planet or planet-satellite system, then, in principle, it can be derived for other planets and satellites, provided that the bodies impacting the various planets and satellites are dynamically related.