April 15 Lunar Eclipse from a Different Perspective: What Would an Astronaut See from the Moon?

The Moon during totality of the October 27, 2004, total lunar eclipse. U.S. Navy image 041027-
N-9500T-001. Credit:  Scott Taylor, USN.

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A lunar eclipse is one of the easiest astronomical phenomena to observe without the aid of a telescope. Lunar eclipses are also relatively common, occurring about twice a year. In 2014, the first eclipse will occur on the night of April 14–15 and the second will occur on the night of October 8.

When a lunar eclipse occurs, the Moon is moving through the Earth’s shadow. If there are clear skies in your area, you can watch the lunar surface darken, then slowly turn a bright red color over the course of a couple of hours. While watching the eclipse, you might ask yourself what it might look like if you (or your favorite astronaut!) were on the surface of the Moon instead of on Earth.

View from the Nearside of the Moon
An astronaut looking up from the nearside of the Moon would actually observe a solar eclipse, not a lunar eclipse. From his or her viewpoint, Earth is passing in front of the Sun, obscuring the Sun from view.

During the eclipse, an astronaut would see the dark nightside of Earth slide in front of the Sun until it was completely rimmed with light. This spectacular ring of light was seen by Japan’s Kaguya spacecraft when it was in orbit around the Moon during an eclipse on February 10, 2009.

While the ring of light dominates the astronaut’s view of the sky, the lunar surface underfoot and on the surrounding mountain peaks would be bathed in red light. This red coloring is due to Earth’s atmosphere acting as a lens, bending the Sun’s light and scattering blue light while allowing red light to pass through and eventually reach the lunar surface.

Because Earth is blocking the Sun and most of its light from view, temperatures would begin to fall. During the June 15, 2011, lunar eclipse, the Diviner instrument onboard the Lunar Reconnaissance Orbiter observed the temperature of the lunar surface drop more than 100°. An astronaut’s spacesuit can accommodate the change in temperature, but his or her visibility would be affected. Low light levels might make it more difficult (but not impossible) to see and might affect depth perception.

View from the Farside of the Moon
A new generation of astronauts will likely explore the lunar farside, a terrain shaped by immense impact craters and mountain peaks. It is one of the best locations in the solar system for determining the answers to fundamentally important questions about planetary origins and evolution. It is also one of the key locations suitable for developing a productive and sustainable presence in space. One of the most interesting locations on the Moon’s farside is the Schrödinger impact basin, which is located within the immense South Pole-Aitken basin. Exploring Schrödinger basin would address the two highest science priorities and more than half of the scientific objectives outlined by the National Research Council report The Scientific Context for Exploration of the Moon.

Commander Gene Cernan of Apollo 17 captured this spectacular image of Lunar Module Pilot Harrison Schmitt with the American flag and a view of Earth. During an eclipse, the face of Earth in the sky above the flag would be dark and outlined by a ring with light. In the foreground, on the lunar surface, light levels would fall and the spacesuit would reflect reddened light. NASA Image AS17-134-20384.

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Positions of the Sun, Earth, and Moon during a lunar eclipse.
(Not to scale.) Credit: Smithsonian Institution.

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What would an astronaut exploring the farside of the Moon experience during a lunar eclipse? In short, nothing. Lunar eclipses occur when Earth is positioned between the Moon and the Sun. Because the farside of the Moon faces away from Earth, an explorer on the lunar farside would not see the Sun disappear or the lunar surface reddened, nor would they feel temperatures fall. Indeed, they would be completely unaware that an eclipse had even occurred. They would, however, be dealing with low light levels, because they would be in the midst of a 14-day long period of darkness — the lunar night — while the nearside was experiencing the eclipse.

Techniques for living and operating in those nighttime conditions have been developed and, in some cases, simulated in lunar analog terrains. For example, in 2010, the NASA Desert Research and Technology Studies (Desert RATS) team simulated a 28-day mission to the Malapert Massif on the lunar farside, including the deployment of two rovers with astronauts during a lunar night. Operating without sunlight for power in future missions will be challenging, but is something that can be accommodated for short periods of time.