BY MARK MATHOSIAN
What colors do you see when you look at the Moon? Your answer is probably shades of white and gray. So, you may be surprised to learn the Moon is actually quite colorful, with countless shades of yellow, orange, blues, browns and purple. It’s just that for most of us, our eyes are not sensitive enough to distinguish them, even through a telescope. The easiest way to see the colors is by examining enhanced digital photographs of the Moon’s surface. Highly sensitive camera lenses capture muted colors. Although a tweaked photograph is needed to expose delicate hues and shades, American astronauts astutely observed a few colors on the Moon while orbiting in their spacecraft during Apollo 12 in 1969.
In a post flight report, Astronauts Charles “Pete” Conrad and Alan Bean noted, “The first day, everything appeared to be dull gray. If we looked very closely, of course, now and then it was possible to observe a white rock or, in an area where we had disturbed the soil, perhaps a slightly different shade of gray. Between the first and second days, definite color change accompanied the Sun-angle change. On the second day, everything that had appeared to be gray on the first day started looking either a dark or a tannish brown.”
Why are there different colors on the Moon? Simple answer: The moon’s surface consists of many different minerals. These colorful minerals pop out in photographs enhanced with software like Adobe Photoshop. For example, blue pops out from titanium rich minerals on Mare Tranquillitatis and the impact crater Aristarchus. Shades of brown appear on Mare Serenitatis, a basaltic lunar plain rich in iron from ancient lava flows. Dried lava beds, craters, and rocks all have subtle color differences visible in processed photos. To learn more about the colors of the Moon, get a copy of SkyatNight Magazine,Patrick Moore’s Guide to the Moon.This collector’s edition contains an excellent article with a labeled map and color photographs.
Let’s move on to the Moon’s smell. First I’ll set the scene. When astronauts walk on the Moon, their spacesuits get covered with lunar dust called regolith. Regolith is fine gray lunar soil and rock fragments from bedrock blended with silicon dioxide glass created by meteoroids crashing into the moon’s surface. The meteoroids have been smashing into the moon for billions of years, and heat from their impacts fuses the meteoroid material with lunar topsoil creating the glass that shatters into tiny sharp pieces. The glass bits also become mixed with elements on the Moon such as iron, calcium and magnesium. You may wonder how you can smell anything on the Moon since it has no air. The answer is, you can’t. Astronauts didn’t smell the moon dust until after they returned to the command module and removed their spacesuits.
Astronauts Jack Schmitt and Gene Cernan on the Apollo 17 mission said that when they got undressed, they handled and smelled the dense lunar topsoil. Schmitt radioed to NASA in Houston that the odor was quite strong. “When I took my helmet off after the first EVA (extra-vehicular-activity), I had a significant reaction to the dust. My turbinates (cartilage plates in the walls of the nasal chambers) became swollen.” Astronaut Cernan further described the smell in the lunar module as “spent gunpowder,” commenting that the Moon dust “smells like someone just fired a carbine in here.” They also said they could taste the metallic-like substance in the middle of their tongues. Interestingly, the powerful stench of the lunar dust gave Astronaut Schmitt the first case ever of extraterrestrial hay fever. With a congested voice he radioed to Houston that hay fever like symptoms came on “pretty fast.”
So, there you have it. The Moon is truly a colorful place, not just shades of white and gray. It smells like a spent shotgun shell and causes hay fever like symptoms if you ingest its dust. No doubt there will be more revelations after future Moon missions. You can look forward to reading about them in future columns of & Another Thing.