PLANET VS CRATER SIZE
|SOLAR SYSTEM BODY
||PEAK RING km
||~110 – ~400
||10 – 110
||>50 – 60
||10 – ~50
||<10 – 20
||~30 – ~100
||5 – ~30
||175 – 220
||30 – 175
The depth to diameter ratio of craters smaller than a certain size is a constant, as predicted by the Maxwell Z-model. Below a break point (10 km for the Moon), the ratio follows a power law, decreasing as size increases [Hiesinger, 2006, Sharpton, 1994]. Source: [Hiesinger, 2006].
The primary factors governing the size and shape of impact craters are the impact energy, gravity and properties of the target. Gravity affects the cratering process by influencing the dimensions of the excavation bowl, the extent of the ejecta and various post-impact crater modifications. In the modification stages of impact cratering, gravity influences the degree of slumping, perhaps governing the size of potential central uplifts (Greeley 2011).
The Earth is immersed in a swarm of Near Earth Asteroids (NEAs) capable of colliding with our planet, a fact that has become widely recognized within the past decade. The first comprehensive modern analysis of the impact hazard resulted from a NASA study requested by the United States Congress. This Spaceguard Survey Report (Morrison 1992) provided a quantitative estimate of the impact hazard as a function of impactor size (or energy) and advocated a strategy to deal with such a threat (Morrison, 2007).
A comparison between the terrestrial, Cytherean and lunar cratering records indicates that the large craters (diametersD>D0) on these surfaces all have cumulative numbers that are proportional to D-2.59±0.05. Atmospheres have a negligible effect on the formation of D>D0 craters. It is shown that this limiting diameter is 45±3 km in the case of Venus, and 21.0±1.5 km in the case of Earth. In this large-diameter range, there are about 1.51±0.34 times more craters, per unit area, on Venus than on the Earth, and about 1350±310 times more craters, per unit area, on the Moon than on the Earth. (Monthly Notices of the Royal Astronomical Society 11 August 2002)
Greeley, R. 2011, Planetary Geomorphology, Cambridge.
Grieve, R.A.F. 2006, Impact Structures in Canada, Geological Association of Canada.
Morrison, D. 2007 The Impact Hazard: Advanced NEO Surveys and Societal Responses, Comet/Asteroid Impacts and Human Society 2007, pp 163-173
Wood, C.A. 2003, The Modern Moon, Sky Publishing