The impact of the Kasatochi eruption on the Moon's illumination during the August 2008 lunar eclipse

• Published in: Geophysical research letters Vol. 38; no. 14
• Main Authors: García Muñoz, A., Pallé, E., Zapatero Osorio, M. R., Martín, E. L.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01-07-2011; American Geophysical Union; John Wiley & Sons, Inc
• Subjects: aerosol; Atmospheric sciences; Biological oceanography; Chemical oceanography; Earth sciences; Earth, ocean, space; eclipse; Exact sciences and technology; Kasatochi; Lunar eclipses; Moon; Radiation; Sunlight; volcanic; Volcanoes; Wavelengths; Sunlight; polar regions; Alaska; United States; Arctic region; USA, Alaska; wavelength; satellites; Earth atmosphere; absorption; Moon; eruptions; Space remote sensing; latitude; volcanoes; Satellite observation; solar radiation; Lunar eclipse; clouds; North America; Earth; Sunlight; Illumination; Polar region; oxygen
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2011GL047981

The Moon's changeable aspect during a lunar eclipse is largely attributable to variations in the refracted unscattered sunlight absorbed by the terrestrial atmosphere that occur as the satellite crosses the Earth's shadow. The contribution to the Moon's aspect from sunlight scattered at the Earth's terminator is generally deemed minor. However, our analysis of a published spectrum of the 16 August 2008 lunar eclipse shows that diffuse sunlight is a major component of the measured spectrum at wavelengths shorter than 600 nm. The conclusion is supported by two distinct features, namely the spectrum's tail at short wavelengths and the unequal absorption by an oxygen collisional complex at two nearby bands. Our findings are consistent with the presence of the volcanic cloud reported at high northern latitudes following the 7–8 August 2008 eruption in Alaska of the Kasatochi volcano. The cloud both attenuates the unscattered sunlight and enhances moderately the scattered component, thus modifying the contrast between the two contributions.
Key Points
Scattered sunlight contributes to the illumination of the eclipsed Moon
The Kasatochi volcanic cloud leaves a signature on the eclipse spectrum
The effect of meteoritic dust is likely masked by the volcanic cloud