Rock-Art Image in Fern Cave, Lava Beds National Monument, California: Not the AD 1054 (Crab Nebula) Supernova

Article excerpt

On 4 July AD 1054 a supernova brighter than Venus appeared in the sky, remaining visible for approximately 23 days and 650 nights. It was chronicled in five independent historic accounts, four from China and one from Japan (Duyvenduk 1942). Hubble (1928) suggested that the Crab Nebula is a result of the AD 1054 event, a view generally accepted (Clark & Stephenson 1977). For at least 40 years investigators have attributed certain distinctive rock paintings and carvings in the western United States as recordings of the AD 1054 supernova. More than 20 such depictions (circle or star-like symbols and a crescent) have been located (Brandt & Williamson 1979). In particular, two panels of rock paintings in Lava Beds National Monument, California [ILLUSTRATION FOR FIGURE 1 OMITTED], one at Fern Cave and one at Symbol Bridge, were listed as recording the AD 1054 supernova. Brandt et al. (1975: 52), noting that the orientation of the moon and supernova are not correct in the Fern Cave rock painting, concluded that 'errors in recording the orientation of the crescent moon are common'. The only direct means of assessing the likelihood that a 'supernova' representation records the AD 1054 event is to date the rock painting or carving. In our laboratory at Texas A&M University, we developed a plasma-chemical extraction technique that permits analysis of 14C in rock paintings, whether the pigments used were charcoal or inorganic iron- and manganese- oxides and hydroxides with organic binder/vehicles (Ilger et al. 1996). This paper presents direct 14C age estimates on rock paintings that have been suggested to represent the AD 1054 supernova. The AMS 14C analysis on each sample using our plasma-chemical extraction technique shows that these images do not represent the AD 1054 supernova.

Experimental procedure

We took charcoal pigment samples from three figures in proximity at Fern Cave: a crescent pointing downward and two near-by circles, one above and one below the crescent [ILLUSTRATION FOR FIGURE 2 OMITTED]. Small amounts of charcoal were scraped from the crescent and two circles individually. Rubber gloves were worn to avoid contamination during sampling and all subsequent handling. Each charcoal sample was placed on aluminium foil, wrapped, and sealed in a plastic bag. The motif was photographed before and after sample collection. Damage incurred to the three paintings was so small that it was difficult to determine by visual inspection where the sample was removed.

The samples were treated with 1 M NaOH and sonicated at 50 [degrees] C, a standard procedure used to remove possible humic and fulvic acids that might contaminate the charcoal to be analysed for 14C. Humic and fulvic acids are brownish-yellow in NaOH. It took 8-10 one-hour treatments with NaOH before the solutions appeared clear; we then did three additional extractions to ensure complete removal of the humic and fulvic acid components. Neutralization of the NaOH solutions with 1 M HCl produced no humic acid precipitate; thus the brownish colour was likely due to fulvic acids. The NaOH-treated charcoal samples were then rinsed with doubly distilled, de-ionised water, filtered and dried; they were then ready for plasma-chemical extraction of the organic carbon for 14C analysis.

In preparation for the extraction, we use radio-frequency generated, low-temperature ([less than]175 [degrees]) oxygen plasmas to remove organic material as C[O.sub.2] from the empty reaction chamber. Argon plasmas are used on the sample after its insertion into the chamber to remove adsorbed C[O.sub.2] from the system. Finally, oxygen plasmas are utilized on the paint sample to convert the organic carbon to C[O.sub.2], leaving the substrate rock and accretion carbonates and oxalates intact. This organic carbon is then analysed by AMS. Experimental details, reported in our previous paper (Ilger et al. 1996), are not repeated here. Since the introduction of our plasma-chemical technique in 1990, we have demonstrated its validity on numerous samples of known 14C content: charcoal (two dated previously by Beta Analytic, Inc. …