October 4, 2004 | David F. Coppedge

Dating of Crater Rays Needs Overhaul

A dating method relied on by planetary geologists needs drastic revision, according to Planetary Science Research Discoveries (PSRD) scientists at the University of Hawaii.  Crater rays are the streaks that extend radially from impact craters.  Previously, planetary scientists assumed they darken over time under bombardment from the solar wind and can be used as indicators of young and old craters.  This overlooks factors like the brightness and composition of the underlying material, the effect of secondary craters, and the amount of mixing of new and existing material, and the actual darkening rate.  Dates estimated without knowledge of these conditions can apparently be in error by large margins.
    The researchers compared data on lunar crater rays from the Clementine lunar spacecraft, Apollo moon samples, and spectra from Arecibo radar and other instruments, and found that “the mere presence of crater rays is not a reliable indicator that the crater is young, as once thought,” according to the press release by Linda M. V. Martel.  The lunar crater Copernicus had often been used as a model for classifying craters as older or younger than the so-called C/E boundary between two conventional lunar epochs labeled Copernicus and Eratosthenes.  The younger, “Copernican” craters have sharp rims and bright rays.  But estimates from crater counts on lava flows around a classic “Copernican” crater, Lichtenberg, are much older.  “It follows that the mere presence of rays is not a reliable indicator of crater age,” Martel concludes,

And it is no longer valid to assign a Copernican age to craters based only on the presence of rays.
    [B. Ray] Hawke [U of Hawaii] and others conclude that a new method using the optical maturity parameter is required to distinguish Copernican from Eratosthenian craters.  They acknowledge a problem of not knowing the time required for a surface to reach full optical maturity; no such age has been firmly established.
    A possible solution was proposed by Jennifer Grier (formerly at the University of Arizona and now at the Harvard-Smithsonian Center for Astrophysics) and Al McEwen (University of Arizona) and colleagues.  Their work showed that if the ejecta of Copernicus crater were slightly more mature, it would be impossible to tell apart from the optically mature bedrock.  Since the commonly accepted age of Copernicus is about 0.8 billion years, then perhaps full optical maturity occurs at about 0.8 billion years.  More work is necessary and future studies will look more closely at optical maturity maps of the Copernicus crater region to better define the C/E boundary in the lunar time scale.

Unfortunately, pinning down absolute ages by radioactive dating methods will require more samples from the moon, Martel says, so the uncertainty will be around awhile.

Another dating method is found to be deficient by the daters themselves.  Ask yourself the next logical question.  How are we to know that the “commonly accepted” ages of these formations have any validity?  After all, the previous estimates were considered valid till now.  How can anyone have confidence that the assumptions used to determine these dates, the dates remaining after this latest “whoops” report, are just as flawed as the assumptions that were used to date crater rays?   You can’t calibrate assumptions against assumptions, and nobody was there with a stopwatch to provide a real absolute age.  There are some things science cannot know for sure, such as processes extrapolated back in time when there were no observers.
    Readers had better be armed with good baloney detectors before swallowing the millions and billions tossed out so glibly by “experts” who weren’t there and can’t possibly know such things without assuming the very things they need to prove (see 10/09/2003 headline).   We’ve indicated many times that the assumed age of the solar system (4.6 billion years) is rarely if ever questioned; it is taken on faith by most researchers as a given (see, for example, the 05/13/2003 headline), yet is based on flawed, assumption-ridden premises (see 08/12/2003, 06/05/2003, 02/22/2002 and 10/25/2001 headlines).  As a consequence, they are often found force-fitting uncooperative data into it, just like they are doing here with lunar craters.  Who cares whether “most scientists accept” a date that fits into the currently fashionable (i.e., evolutionary) timeline, especially when it was arrived at by ignoring other dates that don’t fit?  Consensus doesn’t cut it in science (see 12/27/2003 editorial).  Let this latest admission be a lesson: geological dating is a splintered reed that will pierce the hand of anyone who leans on it.

(Visited 16 times, 1 visits today)
Categories: Solar System

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.