May 2016’s Waning Gibbous Moon Shows Dark Mare Imbrium

Summary: May 2016’s waning gibbous moon, from Monday, May 23, to Saturday, May 28, shows dark Mare Imbrium in the northwest lunar sector.

near side major maria and craters of Earth's moon: Peter Freiman/Cmglee/Gregory H. Revera, CC BY SA 3.0, via Wikimedia Commons

May 2016’s waning gibbous moon, shining from Monday, May 23, to Saturday, May 28, shows dark Mare Imbrium to moon gazers at temperate or high latitudes in the Northern Hemisphere.

Mare Imbrium is located in the northwestern lunar sector. From an Earth-based perspective, Mare Imbrium is located on the left side of the lunar disk. From a moon-based perspective, Mare Imbrium occupies the lunar disk’s right side.

The dark lunar feature consists of a somewhat flat layer of basaltic lava superposing an impact basin. Known singularly as lunar mare and plurally as lunar maria, dark basaltic plains cover approximately 16 percent of the lunar surface. Mare Imbrium measures a diameter of 1,145.53 kilometers (711.79 miles).

Mare Imbrium has the folkloric honor of representing one of the eyes of the iconic Man in the Moon image that dominates the full phase of the lunar cycle for Northern Hemisphere moon gazers. According to perspective, the dark plain serves as the Man in the Moon’s left or right eye. From an Earth-based perspective, Mare Imbrium contributes the left eye to the face and Mare Serenitatis, in the northeastern quadrant, supplies the right eye. From a moon-based perspective, Mare Imbrium is the image’s right eye.

As the Man in the Moon, Mare Imbrium joins other examples of lunar pareidolia (Ancient Greek: παρα, para, “concurrent, alongside” + εἴδωλον, eídōlon, “image”). The psychological phenomenon of pareidolia perceives familiar patterns, such as animals, faces or objects, in unrelated objects or shapes. The complex play of dark and light areas across the moon’s surface is conducive to perceptions of lunar pareidolia.

Mare Imbrium is visible to unaided eyes in the Northern Hemisphere, especially during full, gibbous and last quarter phases. For temperate- and high-latitude viewers, the left side of the lunar disk is illuminated during waning phases.

The full moon is not necessarily the best phase for aided viewing of Mare Imbrium and other features with binoculars and/or telescopes. A moon filter is advisable in order to dim the full moon's extreme brightness. Interesting details and perspectives emerge via the contrasts that characterize the light and shadow plays of other phases.

In the Southern Hemisphere, Mare Imbrium is visible during full and waxing phases. The Southern Hemisphere’s inverted perspective of the moon accounts for darkening and lightening of opposite sides for waxing and waning phases. Accordingly, the left side is illuminated during waxing phases for temperate- and high-latitude viewers in the Southern Hemisphere.

May 2016’s waning gibbous moon succeeds the full phase as of Monday, May 23. The moon’s waning gibbous phase indicates that the lunar disk is more than half illuminated for observers on Earth.

Moonrise times span late evening to after midnight for May 2016’s waning gibbous moon. The waning gibbous moon rises Monday, May 23, at 9:55 p.m. Eastern Daylight Time (01:55 Coordinated Universal Time); Tuesday, May 24, at 10:45 p.m. EDT (02:45 UTC); Wednesday, May 25, at 11:32 p.m. EDT (03:32 UTC); Friday, May 27, at 12:15 a.m. EDT (04:15 UTC); Saturday, May 28, at 12:55 a.m. EDT (04:55 UTC).

Moonset times edge their way through the morning for May 2016’s waning gibbous moon. The waning gibbous moon sets Tuesday, May 24, at 8:09 a.m. EDT (12:09 UTC); Wednesday, May 25, at 9:02 a.m. EDT (13:02 UTC); Thursday, May 26, at 9:58 a.m. EDT (13:58 UTC); Friday, May 27, at 10:58 a.m. EDT (14:58 UTC); Saturday, May 28, at 12:01 p.m. EDT (16:01 UTC).

Scrutinizing Mare Imbrium, with aided or unaided eyes, reveals the plain’s interesting neighbors. For example, Sinus Iridum (“Bay of Rainbows”) bulges as a northwestern extension. Aristarchus and Copernicus shine as prominent, rayed impact craters, with bright radial streaks of ejecta, or ejected material, along Mare Imbrium’s southwestern and southeastern extents, respectively.

Jesuit astronomer Giovanni Battista Riccioli (April 17, 1598-June 25, 1671), who extensively studied the moon, gave the Latin name to the prominent, dark lunar feature. Mare Imbrium translates as “Sea of Showers.”

The takeaway for the showing of dark Mare Imbrium by May 2016’s waning gibbous moon is that the Man in the Moon’s right eye (or left eye, depending upon perspective) represents a real feature that easily disassociates itself from the anthropomorphic, or humanlike, illusion during waning and waxing phases.

Sinus Iridum, a northwestern extension of Mare Imbrium: LROC (Lunar Reconnaissaince Orbitaer Camera) WAC (Wide Angle Camera) reveals Sinus Iridum's topography, with blue showing lowest areas and red showing highest areas: NASA/GSFC (Goddard Space Flight Center)/Arizona State University, Public Domain, via NASA Missions/LRO Multimedia

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

near side major maria and craters of Earth's moon: Peter Freiman/Cmglee/Gregory H. Revera, CC BY SA 3.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Moon_names.svg

Sinus Iridum, a northwestern extension of Mare Imbrium: LROC (Lunar Reconnaissaince Orbitaer Camera) WAC (Wide Angle Camera) reveals Sinus Iridum's topography, with blue showing lowest areas and red showing highest areas: NASA/GSFC (Goddard Space Flight Center)/Arizona State University, Public Domain, via NASA Missions/LRO Multimedia @ http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20101015-sinus-iridum.html

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