1990 12 06 Nature - Vol 348 - Earthquake lights

Magazine Overview

This issue of Nature, dated 6 December 1990, features a 'Scientific Correspondence' section with two distinct articles. The first, authored by Marcel Quelet, investigates the phenomenon of earthquake lights (EQLs) and their correlation with seismicity in the Saguenay region of Quebec, Canada. The second, by Robin Holliday, delves into molecular asymmetry in RNA structures and its implications for embryonic development.

Earthquake Lights and Seismicity

The article by Marcel Quelet reports on EQL sightings that occurred between 1 November 1988 and 21 January 1989 in the Saguenay region, an area experiencing significant seismic activity. A network of portable seismometers recorded 54 seismic shocks, including a foreshock of magnitude 4.8 on 23 November and a main shock of magnitude 6.5 that was felt as far south as Washington, DC.

Quelet and his colleagues surveyed 52 reporters who witnessed these phenomena. They identified three types of luminescence: sparkings without sound, diffuse light similar to heat-lightning, and vertical and horizontal aurora-like stripes. Fireballs, a few metres in diameter, were frequently observed, sometimes appearing to pop out of the ground or hovering in the air, occasionally accompanied by dripping droplets. The reported colours were predominantly orange, yellow, white, and green. Most EQLs (70%) were observed 4-35 km north of the epicentral area, aligning with the geographical distribution of the main cities in the region.

Remarkably, EQL sightings were reported as early as 1 November, preceding the main seismic events detected by the permanent Charlevoix seismic-monitoring station. Out of 46 EQLs reported between 1 November 1988 and the end of January 1989, 39 (84%) were seen during November. The timing of the main seismic shocks and their aftershocks in November was highly synchronous with the daily number of EQL sightings. For instance, on 23 and 25 November, 11 sightings were reported around 0412 and 1846 EST, respectively. While seismic activity was recorded, the EQL events were often underreported due to the time of night.

The article notes that while seismic events of magnitude greater than 0.1 are detected by the seismometer network, discrepancies exist in statistical analysis due to the nature of EQL reporting. Nevertheless, a correlation was observed between seismic shocks and EQLs in January 1989, with six EQLs synchronized with five seismic shocks.

Several suggestions have been made to explain these luminous seismotectonic electromagnetic emissions, but a fully satisfactory explanation remains elusive. The complex interplay of physical and chemical factors associated with seismic events, coupled with the difficulty of gathering controllable field information on such rare phenomena, limits research progress.

Molecular Asymmetry in Embryonic Development

In a separate piece of scientific correspondence, Robin Holliday discusses the concept of molecular asymmetry in RNA structures. He proposes that these asymmetric molecules, encoded by maternal DNA, could function as important cytoplasmic determinants in the egg and developing embryo. Holliday cites the example of snail shell coiling direction, which is known to be maternally inherited, as a potential manifestation of such genetic control over asymmetry.

He suggests that the specific orientation of bases within RNA molecules, particularly in stem loops, could lead to asymmetry. This asymmetry might be recognized by proteins, leading to differential binding and thus influencing developmental pathways. Holliday posits that mutations affecting these asymmetric molecules could result in the reversal or loss of asymmetry, providing a mechanism for inherited traits.

Recurring Themes and Editorial Stance

This issue highlights the interdisciplinary nature of scientific inquiry, bridging geology, physics, and biology. The editorial stance appears to be one of encouraging the reporting and investigation of anomalous phenomena, such as earthquake lights, while also exploring fundamental biological processes like molecular asymmetry and its role in development. The 'Scientific Correspondence' format suggests a platform for brief, focused contributions on cutting-edge or intriguing research findings, inviting further discussion and investigation within the scientific community.