Scientific American Sep 2018

September 2018 ScientificAmerican.com 17

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SPACE

Moon Mystery

The recovery of missing tapes

reveals the cause of lunar heating

When Apollo astronauts returned from

the moon in the 1970s they left behind two

pairs of temperature probes drilled into the

surface. The sensors measured how easily

the soil radiated heat in the hope of learning

how much radioactive heating the moon

produced and details about its

recent geological activity.

The nuclear-powered lunar

šxDî‹ ̧ÿÇß ̧UxäUß ̧Dl`Däî

data back to Earth where they

were stored on tapes until 197 7.

But the experiments’ principal

investigator Marcus Langseth

studied it only through Decem-

ber 1974. The remaining tapes

were thought to be lost be -

cause sloppy paperwork failed

to document their location. But

̧þxßîšxÇDäîlx`DlxD³x† ̧ßî

to scour attics garages and government

facilities for information led to the recovery

of a handful of the missing tapes.

Langseth’s report on the original data

revealed that heat was moving downward

from the moon’s surface rather than up

from the core as would be expected. Sev-

eral theories emerged to explain the phe-

nomenon: that the astronauts’ presence

had somehow warmed the surface; that

the instruments themselves had produced

excess heat; or that the moon was going

through a long-term warming cycle. The

uncertainty meant scientists could not trust

the experiments’ results.

But the newly recovered tapes reveal

that heat traveled all the way from the

lunar surface to the bottoms of the bore-

holes ruling out every explanation except

for surface disturbance by the astronauts.

As they explored the moon their footprints

and rover tracks compressed and darkened

its surface. “It was the [absorption of] sun-

light from where the astronauts were walk-

ing around that caused the moon to get

š ̧îîxߞ³îš ̧äxäÇx`ž‰`§ ̧`Dîž ̧³äjÚäDāä

study co-author Walter Kiefer of the Lunar

and Planetary Institute in Houston. The

results were published in May in the Journal

of Geophysical Research: Planets.

5šx‰³lž³ääøxäîîšDî­xDäøßx­x³îä

taken at the start of the experiments—

when the heat was still near the surface—

were the most reliable making the original

data correct. “We now know we can trust

those measurements in a way that we were

³ ̧îäøßx ̧…D…xÿāxDßäD ̧jÚ!žx…xßäDāäÍ

— Nola Taylor Redd

© 2018 Scientific American

From the New York Times bestselling

and award-winning author of the Three-Body Trilogy

“A breakthrough book...a unique blend of

scientifi c and philosophical speculation politics

and history conspiracy theory and cosmology.”

—GEORGE R. R. MARTIN

on The Three Body Problem

“Wildly imaginative really interesting.”

—PRESIDENT BARACK OBAMA

on the Three-Body Problem trilogy

“Extraordinary.”

—THE NEW YORKER

on The Three Body Problem

tor-forge.com
Translated by Joel Martinsen

A new science fi ction adventure about a young man searching for the

answers to the mysterious natural phenomenon that killed his parents

and in the process discovering a new dark frontier of reality.

Also available from Macmillan Audio