Jack Skis the Moon

By Dr. Tony Phillips

What a ski report. Clear skies, no wind, sweet slopes and deep
powder\--not expected to melt for at least five billion years. Grab your
poles and pack your bags!

Just don't forget your spacesuit, because you're going to the moon.

The moon's dust-covered mountains reminded more than one Apollo
astronaut of a winter wonderland: "My snowsuit's ready," joked Apollo 14
astronaut Ed Mitchell after donning his spacesuit for a walk around Fra
Mauro. Commander Al Shepard agreed, "You\'re ready to go out and play in
the snow."

"Oh, boy, it\'s *beautiful* out here!" radioed Apollo 15 astronaut Jim
Irwin from his landing site near the sinuous Hadley Rille. Underfoot,
the soil was cushiony like "soft powder snow." He told Houston,
"\[This\] reminds me of Sun Valley (a ski resort in Idaho)." Towering
11,000 feet above Irwin, Mt. Hadley Delta looked "like Dollar Mountain
at Sun Valley, a practice hill with great skiing conditions."

(After the mission, Irwin lamented "if I\'d realized that Sun Valley was
going to invite me up as their guest, I would have mentioned all the
other great ski areas in the world!)

"Man this is a fun ride!" exclaimed astronaut Charlie Duke as he
test-drove the Apollo 16 moon buggy around the Descarte Highlands.
"Occasionally, the back end breaks loose," he reported, "but there\'s no
problem." In the passenger seat, commander John Young chipped in, "It's
just like driving on snow, Houston. By golly!"

Strange but true: A quarter million miles from Earth on a bone-dry world
where the midday sun heats the ground hotter than boiling water, Apollo
astronauts couldn't stop talking about snow.

No one had the bug worse than Apollo 17 geologist Harrison "Jack"
Schmitt.

"Too bad I don\'t have my skis!" he called out from a geology-stop in
the mountain-lined Taurus-Littrow Valley.\
\
"Jack, did you get a pan up here?" Commander Gene Cernan reminds Schmitt
to photograph the site.\
\
Schmitt: "No, I forgot. I got interested in skiing."\
\
"I'll get one (mock sigh)," says Cernan, who does the job himself.

Jack switches to a two-footed skiing stance and makes repeated sounds of
skis gliding: "Shhh. Shhh. Shhh. Shhh. Shhh. Shhh. Whoo! Can\'t keep my
edges. (Pause) Shhhoomp. Shhhoomp. Little hard to get a good hip
rotation," he radioed to Houston.

Using trial and error to refine his technique, Schmitt quickly developed
a no-gear method for lunar skiing. Call it "lunar cross country skiing."

Thirty-five years later, he explains: "You can ski *above* the
moondust---and I did. Imagine swinging your arms and legs cross-country
style. With each push of your toe, your body glides forward above
ground. Swing, glide, swing, glide. The only marks you leave in the
moondust are the toe-pushes."

Cernan called this "loping," and he didn't think so much of it,
preferring his own "kangaroo hop" for locomotion. But that's another
story.

If he could've, Schmitt would have tried downhill skiing. "I think
downhill techniques would work very well on the moon," he says. "You
even have built-in moguls, the impact craters on the slopes. The moon's
low gravity would allow all kinds of jumps and hops that you might find
difficult on Earth."

There's just one problem: Unlike true snow, "moondust is very abrasive."
Apollo astronauts found this out when it got on their spacesuits.
Moondust infiltrated every nook and cranny, causing air leaks, binding
joints and scratching ball bearings. It was a tremendous nuisance.

Moondust is abrasive because of the way it is formed---by violence. For
billions of years, asteroids large and small have been hitting the
moon's surface, shattering rocks and fusing topsoil into "pyroclastic
glass." The ceaseless pounding (which still goes on today) has rounded
the moon's jagged mountains into ski-friendly slopes and coated the moon
with a powdery residue of broken glass and sharp-edged rock\--moondust.

"To ski the moon, you'd need gear that could slide over this very
abrasive material. Maybe Teflon-coated skis would work," Schmitt
suggests. (Teflon has the lowest coefficient of friction of any known
solid material.)

It's not such a crazy idea. Here on Earth, people ski on sand dunes, for
instance, at the Great Sand Dunes National Park in Colorado. Ordinary
skis sprayed with silicon lubricant or WD-40 shoot down the dunes as if
they were groomed snow trails. Sleds fashioned from cardboard and duct
tape work well, too.

But, cautions Schmitt, "moondust is much more abrasive than sand."
Typical grains of Earth-sand measure 500 microns across and have rounded
edges. They easily slip, slide and roll. A typical grain of moondust, on
the other hand, measures less than 100 microns wide and has very sharp
edges. The fine grains lock together "like Velcro," says Schmitt, "and
scratch anything that comes in contact with them." A Teflon ski-coating
might not last long.

Time to invent a new material? According to the Vision for Space
Exploration, NASA is going back to the moon, with a first wave of
astronauts due to arrive in 2018 or so. The long-term goal is to
establish a permanent outpost. Skis and sleds might come in handy for
workaday transportation or weekend recreation.

Schmitt wishes he could go, too. The ski report is out of this world.

"We're going back to the Moon," says Schmitt, referring to the Vision
for space Exploration, which aims to establish

Apollo 16

**124:49:04** Duke: Man, this is a fun ride. (Pause) Okay, Tony, we\'re
doing 10 clicks.

**124:49:14** England: Outstanding.

**124:49:18** Duke: Occasionally, the back end breaks loose, but
there\'s no problem. This is *really* some machine. (Pause)

**124:49:42** Young: It\'s just like driving on **snow**, Houston. By
golly!

Apollo 15

**120:31:08** Scott: Boy, is this dirt soft! Man!

**120:31:15** Irwin: Like soft powder **snow**.

**120:31:16** Scott: Really is.

**120:31:17** Irwin: Except it\'s a little different. Different. (Pause)