Meteorite Dust and the Age of the Earth

by

Copyright © 1996
[Last Update: September 5, 1996]

Introduction

otivated by watching while the same old arguments are repeated ad nauseum on talk.origins, I decided to acquaint myself, as best I could, with the current state of understanding as to extraterrestrial dust infall to the Earth. It is argued that both the Earth and Moon should be covered with a great layer of space dust if the Earth were as old as the standard models imply. This mini-faq will present the discussion given by Chris Stassen in his "Age of the Earth" talk.origins FAQ file, and then provide an update from the current literature. I make no claim at having done an exhaustive search, but I do think I have done a reasonably thorough search, so my results here are certainly representative of the current state of knowledge in the field. Hopefully, this will help to put an end once-and-for-all to the stale space-dust argument.

"The Age of the Earth" by Chris Stassen

What follows is an excerpt from the talk.origins FAQ file "The Age of the Earth", by Chris Stassen. His target is the meteoritic dust argument as applied to the Moon. However, since the measurements used by the young Earth creation scientists are Earth based, then the argument is equally applicable to the Earth (and has been applied to the Earth by young Earth creationists). I include here the full text of section 3 of the first part of the FAQ, "How Old is the Earth and How Do We Know?". I include this in order to put the argument in proper context for the reader, before going on to describe the current observations and data. I will also reproduce all of the references quoted by Stassen in this section.

[Start of quoted material]

3. Accumulation of meteoritic dust on the moon

This argument: A single measurement of the rate of meteoritic dust influx to the Earth gave a value in the millions of tons per year. While this is negligible compared to the processes of erosion on the Earth (about a shoebox-full of dust per acre per year), there are no such processes on the moon. The moon must receive a similar amount of dust (perhaps 25% as much per unit surface area due to its lesser gravity), and there should be a very large dust layer (about a hundred feet thick) if the moon is several billion years old.

Morris says, regarding the dust influx rate:

"The best measurements have been made by Hans Pettersson, who obtained the figure of 14 million tons per year (1)." (Morris 1974, p. 152) [emphasis added]

Pettersson stood on a mountain top and collected dust there with a device intended for measuring smog levels. He published calculations which measured the amount of nickel he collected, assumed that nickel was only present in meteoritic dust, and assumed that some percentage of meteoritic dust was nickel, to get his final figures (that first assumption was wrong and caused his published figures to be a vast overestimate).

Pettersson's calculation resulted in the a figure of about 15 million tons per year. He believed that estimate to be an over-estimate, and indicated in the paper that 5 million tons per year was a much more likely figure.

Much more accurate measurements were available, from satellite penetration data (no possibility of earthly contamination), by the time Morris published Scientific Creationism. These more accurate measurements give the value of about 18,000 to 25,000 tons per year. These measurements agree with levels of meteoritic dust levels trapped in sediments on Earth. (That is, they are verified by an independent cross-check.)

Morris chooses to pick obsolete data with known problems, and call it the "best" measurement available. His calculations are based on a figure that is nearly three orders of magnitude too high. With the proper values, the expected depth of meteoritic dust on the moon is less than one foot.

For further information, see (Dalrymple 1984, pp. 108-111) or (Strahler 1987, pp. 143-144).

There is a recent creationist technical paper on this topic which admits that the depth of dust on the moon is concordant with the mainstream age and history of the solar system (Snelling and Rush 1993). Their abstract concludes with:

"It thus appears that the amount of meteoritic dust and meteorite debris in the lunar regolith and surface dust layer, even taking into account the postulated early intense bombardment, does not contradict the evolutionists' multi-billion year timescale (while not proving it). Unfortunately, attempted counter-responses by creationists have so far failed because of spurious arguments or faulty calculations. Thus, until new evidence is forthcoming, creationists should not continue to use the dust on the moon as evidence against an old age for the moon and the solar system."

Even though the creationists themselves have refuted this argument, (and refutations from the mainstream community have been around for at least a decade longer than that), the "moon dust" argument continues to be propagated in their "popular" literature, and continues to appear in talk.origins on a regular basis:

(Baker 1976, p. 25)
(Brown 1989, pp. 17 and 53)
(Jackson 1989, pp. 40-41)
(Jansma 1985, pp. 62-63)
(Whitcomb and Morris 1961, pp. 379-380)
(Wysong 1976, pp. 166-168)

[End of quoted material]

These references will be found in my reference section below.

Update: Current Observations

Dohnanyi's 1972 review paper seems to mark the beginning of what I will call the "modern era" in determining the flux of extraterrestrial dust on the Earth and Moon. Dohnanyi's flux is quoted by Dalrymple, 1991, and his formalism is repeated in Yamakoshi, 1994. This table represents a wide variety of disparate techniques, which leads one to be confident that the real number is very close to the reported values. Dohnanyi calculated the influx of extraterrestrial material based on his model for the density of interplanetary dust in the vicinity of the Earth. Kane & Gardner used ground based lidar observatons of mesospheric metals, Love & Brownlee used observed impact flux on the Long Duration Exposure Facility (LDEF), and Ceplecha uses a combination of model and observation. Dohnanyi also quotes a value from Barker & Anders, 1968, based on isotopic abundance ratios in sea floor sediments that estimated 6.12 × 10¹⁰ g/year, with an upper limit of 1.48 × 10¹¹ g/year, which turns out to nicely match Ceplecha's 1996 correction of his own 1992 results. The confluence of answers from model, lidar, sea-floor sediments, and other methods is most invigorating.

TABLE 1 Reported flux rates of extraterrestrial dust onto the Earth, with references, normalized to gm/year over the whole Earth.

Consequential Effect on the Earth

Here I want to examine the effect on the Earth of the dust infall rates given above. I will use Ceplecha, 1996, 1.5 × 10¹¹ grams/year as the assumed infall rate. His 1992 value is slightly larger, but he corrected himself in 1996 based on data not available in 1992.

Calculate total dust fall in 4.5 billion years ...

Total dust fall as a fraction of the current Earth mass ...

[In other words, the Earth's total mass increases by one tenth of one millionth, or one one-hundred-thousandth of a percent, over the entire 4.5 billion years]

Calculate the volume occupied by the total 4.5 billion year dustfall calculated above ... Assume dust density 2.0 g/cm³ (Love, Joswiak & Brownlee, 1994)

Calculate the thickness of a layer of equivalent volume on the surface of the Earth ...

If a plane surface of this area were covered with a thickness of one meter (100 cm) the volume would be 5.10 × 10²⁰ cm³, which is greater than the volume of all extraterrestrial dust. The ratio 3.375/5.10 = 0.6618 gives the true height of the layer in meters, 66.18 cm.

We calculate a layer only 66.18 cm thick after 4.5 billion years, but this is clearly an upper limit for the real thickness. For one thing, the Earth is not flat, and the curvature at the surface of the Earth would cause the real layer thickness to be smaller. Furthermore, we have ignored the fact that the dust is highly porous and very much lacking in mechanical strength. If you actually tried to pile it up 66 cm deep, it would compress significantly due to its own weight.

Comments

[revised January 28 1997]

Although Stassen points out in his FAQ that even many creation science writers have abandoned this argument, it is still popular. Not only does it remain popular on talk.origins, but also with the Creation Research Society (CRS). The CRS has announced its intention to start a ham-radio based project to study meteor encounters with the upper atmosphere, in an expressed effort to revive the extraterrestrial dust argument.

Radio or radar remote sensing techniques are appropriate for the study of meteors, because the radio reflects off of the ionized meteor tracks. However, the scientific research I have cited here is based on in-situ measurements, either of dust in the stratosphere, or of impact features on the Long Duration Exposure Facility, in addition to lidar observations that are guaranteed to be far more sensitive than any radio equipment the CRS is likely to set up. It would seem to be a project doomed to failure, but don't count the CRS out just yet. Expect this argument to continue its regular run on talk.origins, and to increase in frequency of appearance if and when the CRS project actually starts.

[Editor's Note (January 12, 2006): Some young-earth creationists have given up the meteorite dust argument. For example see: Moon-dust argument no longer useful.]

References

The references list contains entries for all of the cited works, plus any other references I think are appropriate to the topic, even if I have not cited them directly. Think of it as a reading list as well as a reference list. All references from Stassen's quoted section are also included.

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