| |
| | Isochrons for Martian Crater Populations of Various Ages |
 | | Tanaka (1986, Table 2) defined crater density limits to the Amazonian, Hesperian, and Noachian relative-age eras, based on the previous work of Scott and Carr (1978) and Condit (1978), for the purpose of stratigraphic mapping of Mars. |
 | | Short, lighter solid lines mark the subdivisions of the Noachian (early, middle, late), Hesperian (early, late – only two subdivisions were defined by Tanaka 1986), and Amazonian (early, middle, late), from the same source. |
 | | A correct interpretation of the area would rely on features that could be found only in the full size spectrum – the older age from large craters and the young flows and their age from small-scale morphologies and the numbers of small craters. |
| www.psi.edu /projects/mgs/chron04a.html (3665 words) |
|