Cosmic Dust on the Moon

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1 Definition
2 Example
3 Discussion
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[edit] Definition

Young Earth Creationists sometimes claim that, given the rate of accretion of cosmic dust on the moon, a 4.5 billion year old moon would be much dustier than it actually is.

[edit] Example

"If anyone reads stories about the moon from prior to the 1960s, one will hear frequently about moon dust. Even in Children's books they talk constantly of the mountains of moondust on the moon. If you look at the moon lander it had huge pads on the bottom to keep it from sinking in the moondust. Neil Armstrong's "small step" was more like a leap off the ladder because they were expecting it to sink in the dust. However, when the measured it, instead of millions of years of space dust, there was only about 6,000 years worth. Odd, huh? Interestly enough, moondust was never mentioned by evolutionists again." [1]

[edit] Discussion

The argument seems to have originated with Henry Morris in his book Scientific Creationism. His calculation of how much dust should be on a 4.5 billion year old moon depends on extrapolating to the moon a figure of 14,000,000 metric tons of cosmic dust per year hitting the Earth. The extrapolation seems to be correct: what is wrong is the figure.

The estimate of 14,000,000 metric tons per year was given in 1960 by a scientist named Petterson: to be precise, this figure was the extreme upper range of his estimate (a fact you will not learn from creationist literature) and was orders of magnitude higher than any estimate given by Petterson's contemporaries.

It is now possible, using satellites, to measure directly just how much cosmic dust there is in space. Based on these measurements, the accretion rate calculated for the Earth is a mere 30,000 ton per year, orders of magnitude below Petterson's estimate. (See Love & Brownlee, "A Direct Measurement of the Terrestrial Mass Accretion Rate of Cosmic Dust", Science 262, 1993[2])

Besides direct measurement, the flux can be estimated using geochemical data. These results are in line with the satelite data:

"The global flux of ET [extraterrestrial] matter to the seafloor, calculated at 30,000±15,000 metric tons per year using Os isotope data for the most suitable marine sediment samples, agrees with the flux of ET matter derived from the LDEF study (40±20 x 10^4 metric tons per year; love and Brownlee, 1993) within uncertainty" (Peucker-Ehrenbrink and Ravizza, 2000)

Similarly, in 1983 Ganapathy calculated a global flux rate of 47-149 x 10^4 metric tons/ yr, based on analyses of iridium in antarctic ice cores.

In short, the estimate used by creationists as the basis of their calculation is several orders of magnitude larger than the figure given by actual measurement. Indeed, the argument might well be stood on its head. Given the actual rate of accretion, a mere 6,000 years would produce a layer of moondust literally microscopic in its thinness. The quantity of dust found on the moon shows, not that it is young, but that it's old.

To their credit, some creationists are abandoning the moondust argument:

"So are there any loopholes in the evolutionists’ case that the current apparent meteoritic dust influx to the lunar surface and the quantity of dust found in the thin lunar surface dust layer and the regolith below do not contradict their multi-billion year timescale for the moon’s history? Based on the evidence we currently have the answer has to be that it doesn’t look like it." (Snelling and Rush, Creation Ex Nihilo Technical Journal, 1993 [3])

Nonetheless, it remains popular with the creationist rank and file.