How Gray Thou Art: The Colors of the Moon

When we look at the Moon from the Earth, we see almost no color. A color image (1) looks almost identical to a gray scale image (2):

The far side of the Moon is similar; it’s grayness looks incredibly bleak with the colorful Earth as a backdrop.

There is some color, though, and when the color differences are enhanced, the distribution and variety of mineral content becomes more apparent: (R. Vanderbei/Princeton photo)

A close-up from the LROC satellite shows some subtle color. (320 nm, represented by blue in this image,  is in the ultraviolet spectrum and is not visible to the human eye).

Views from the surface don’t show any small-scale color variations that are lost in the big pictures; almost all of the color differences are in things the astronauts brought:

Humans tend to grow more sensitive to a given stimulus when the receptors for that stimulus are starved. Did the astronauts “starve” their eyes of color long enough to become more sensitive to it? Indeed, they did:

Jim Lovell of Apollo 8 (1968) described the Moon as “gray — no color.” The astronauts of Apollo 10 reported tan and brown hues, and when astronauts walked on the Moon (Apollo 11, 1969), Aldrin saw traces of purple; Irwin and Scott, on Apollo 15, reported green. The green hue is very subtle; these close-ups shows the “green” rock,  the same image in a colorless gray scale and a color-enhanced photo that confirms that the astronauts were not imagining the green hue:

Apollo 17 astronauts Cernan and Schmitt found orange soil and brought back a sample.


The Moon is virtually a color desert, but like the desert, a closer look reveals that there’s more to the story. The subtle colors, now studied, map the Moon’s geology and may guide mining efforts like the ones in Space Race I: Solar Flare.

Have We Been Quarantined?

The  Fermi-Tipler-Hart question: If there are so many worlds capable of supporting alien life, where are they?

When we talk about where “they” are, we embed a lot of assumptions that reach way beyond a discovery of alien life. Alien life could exist in the form of some self-replicating molecules in a smear of cold, briny slime a few feet under the surface of Mars or Europa. If such molecules are discovered, they won’t be the kind of spacefarers we’re looking for when we’re asking “Where are they?”

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SpaceX – Falcon Whimsy

With Starman traveling through space in  a roadster, SpaceX has merged the very serious (and appropriately so) NASA attitude toward space exploration with the romantic whimsy of Douglas Adams, including a towel. Elon Musk acknowledged the risk, lowered expectations, and let the rocket’s performance and remarkable booster ballet put SpaceX on the front pages.

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