Three Days at Taurus-Littrow

WHEN, if all goes well, Apollo 17's lunar module Challenger makes the final approach for a landing on the moon, it will let down toward a dramatic landscape: a wide valley guarded by three massive, well-rounded mountains that tower as high as 7,000 ft. "Once we're there," insists Apollo 17's commander, Gene Cernan, "I'm going to get us down." He will have little margin for error: only a few miles downrange of Challenger's glide path are the towering Taurus Mountains; to the northeast lies the giant crater Littrow. Much as the landing site for America's sixth (and last) scheduled expedition to the moon's surface will test the astronauts' piloting skills, it should be even more of a scientific challenge. A combination of ancient highlands and a younger lowland valley, the Taurus-Littrow* site promises to provide the moon walkers with two major scientific prizes: the youngest and the oldest rocks yet found on the moon.

The route to Taurus-Littrow will be unusual. Because of the relative positions of the earth, moon and sun in early December, Apollo 17, following the standard trajectory of the moon, would remain in the moon's shadow for nine hours. The spacecraft would, in effect, experience a total solar eclipse, which would screen it completely from the sun's rays and deprive it of essential heat. Thus, to avoid damage to Apollo's systems, the spacecraft will be sent on a trajectory that shortens its "cold soak" to an acceptable two hours. The longer route will add half a day to the total flight time (85 1/2 hours). That change--along with NASA'S requirements for the proper sun angle at the Taurus-Littrow site during landing--make it necessary to launch Apollo 17 at night. Early in the Apollo program, a night launch would have given NASA pause; in the event of an abort shortly after blastoff, the astronauts would have to be fished from the waters of the Atlantic in darkness. But NASA now has such confidence in its launch and recovery techniques that it considers a night pickup to be a relatively safe procedure.

Apollo is scheduled to swing into lunar orbit at 2:49 p.m. E.S.T. Sunday, Dec. 10. Next day, leaving Ron Evans behind in America, the command ship, Cernan and Jack Schmitt will climb aboard the lunar module Challenger, cast off two hours later and, at 2:54 p.m., touch down on the black dust of the Taurus-Littrow Valley. Less than four hours later, Cernan will emerge from Challenger's hatch. His descent down the lander's ladder and the familiar post-landing activities will not be seen on earth. To save weight for scientific experiments and fuel for hovering, mission planners eliminated both the TV connections to the side of the LM and the bulky tripod on which the camera was later mounted.

Picture transmission to earth will begin about an hour after the first EVA (for ExtraVehicular Activity) begins, when the Houston-controlled color TV camera is finally set up on its mounting at the front end of the lunar rover.

A short time later, Schmitt will probably be seen carrying off the familiar dumbbell-shaped package of scientific gear called ALSEP (for Apollo Lunar Surface Experiments Package). At a site some 300 ft. west of Challenger, Geologist Schmitt, with Cernan's help, will set up the five ALSEP experiments, giving space scientists their fifth automatic observatory on the moon (see Lunar Science, page 44). The ALSEP experiment that the scientists are particularly eager to monitor involves two probes that measure the flow of heat from the moon's interior. During Apollo 16, that $1,200,000 experiment was ruined when Astronaut John Young tripped over one of the cables connecting the probes to the central transmitter and ripped the wire loose. To avoid the possibility of a similar accident, all of ALSEP'S external leads have been fitted with stress absorbers--folded tucks in the leads that will come undone if they are tugged too hard.

After buckling themselves into the rover the astronauts will continue their first EVA by driving southeast for about one mile to the edge of a 2,000-ft.-wide crater called Emory. It is here that Schmitt hopes to recover fine-grained dark material, called pyroclastics (literally, broken up by fire), which may be a sign of relatively recent volcanic eruptions. If Schmitt's trained eye happens to spot any interesting material between scheduled stops, he will be able to pick it up without leaving his seat in the rover; at hand will be an extension pole with a device similar to a Dixie cup holder at its far end. After he scoops up a rock or dust with the topmost cup in the holder, Schmitt will remove the cup and its contents, seal the little container and stow it away.

During this EVA, the astronauts will plant the first three of the eight small packages of explosives that NASA calls "the world's safest land mines." Equipped with radio receivers and timers, the packages will be ignited by signals from earth after the astronauts leave the moon. Their blasts--which will register on the ALSEP'S geophones and thus provide data about the moon's interior--may well be seen on earth through the remote-controlled TV camera atop the abandoned rover.

Volcanic Eruption. Refreshed after an eight-hour sleep period, the astronauts are scheduled to start their second EVA at 5:03 p.m. Tuesday, Dec. 12. Heading southwest, they will drive nearly four miles to the base of South Massif and collect samples from a rock-strewn region that scientists believe was formed by a huge landslide from the upper slopes of that mountain billions of years ago. Scientists hope that the rocks consist largely of highland material far older than the relatively young rock of the valley floor. En route back to the LM, the astronauts will stop at a 300-ft.-wide crater called Shorty, which may yield entirely different material: deep-lying rock that was either ejected by a meteor impact or a volcanic eruption that occurred after the landslide covered the area.

The final moon walk will begin at 4:33 p.m. Wednesday, Dec. 13. Cernan and Schmitt will stop at the base of North Massif for more ancient samples. Then they will veer eastward to more gentle slopes, which they have dubbed the Sculptured Hills. Heading south again, they will stop at 260-ft.-wide Van Serg (the puckish pen name of one of Schmitt's Harvard geology professors) Crater, and thread their way through a field of giant boulders that may have been ejected from nearby Sherlock Crater.

In the final hour of the third EVA, Cernan and Schmitt will gather their samples and gear, possibly make a last check of the experimental station and park the rover far enough from Challenger to protect the TV camera from the blastoff. Schmitt will climb back into Challenger first, briefly leaving Cernan alone on the surface of the moon--the last American to stand in lunar dust for some time to come. According to friends, Cernan is planning to say--and perhaps do--something appropriate for the memorable moment.

At 5:56 p.m. Thursday, Dec. 14, Challenger's ascent stage will lift Cernan and Schmitt off the moon to rejoin Ron Evans in the orbiting America. The dramatic launch should be photographed by the rover's camera. Early next morning, Challenger's ascent stage will be sent crashing into the upper slopes of South Massif; the impact will also give seismologists another jolting "look" at the moon's interior. Almost two days later, as the astronauts pass around the far side of the moon for the last time, they will fire America's main engine to kick the ship out of lunar orbit and begin the three-day journey home. At 2:24 p.m. Tuesday, Dec. 19, America should splash down in the balmy waters of the South Pacific, about 350 miles southeast of Samoa, ending the Apollo project's farewell mission to the moon.

*Named for the heavenly constellation Taurus ("The Bull") and the 19th century Austrian astronomer-mathematician Johann von Littrow.

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