The Solar System

CHAPTER 21CHAPTER 2CHAPTER 211 ||| THE MOON AND MERCURY: COMPARING AIRLESS WORLDSTHETHE MOON AND MERCURY: COMPARING AIRLESS WORLDS MOON AND MERCURY: COMPARING AIRLESS WORLDS 444499

■ Table 21-1 ❙ Apollo Lunar Landings

Apollo

Mission*

Astronauts:

Commander

LM Pilot

CM Pilot Date Mission Goals

Sample

Weight

(kg)

Typical

Samples

Ages

(10^9 y)

11 Armstrong

Aldrin

Collins

July

1969

First human landing;

Mare Tranquillitatis

21.7 Mare basalts 3.48–3.72

12 Conrad

Bean

Gordon

Nov.

1969

Visit Surveyor 3; sample

Oceanus Procellarum (mare)

34.4 Mare basalts 3.15–3.37

14 Shepard

Mitchell

Roosa

Feb.

1971

Fra Mauro,

Imbrium ejecta sheet

42.9 Breccia 3.85–3.96

15 Scott

Irwin

Worden

July

1971

Edge of Mare Imbrium

and Apennine Mountains,

Hadley Rille

76.8 Mare basalts;

highland anorthosite

3.28–3.44

4.09

16 Young

Duke

Mattingly

April

1972

Sample highland crust;

Cayley formation (ejecta);

Descartes

94.7 Highland basalt;

breccia

3.84

3.92

17 Cernan

Schmitt

Evans

Dec,

1972

Sample highland crust;

dark halo craters;

Taurus–Littrow

110.5 Mare basalt;

highland breccia

fractured dunite

3.77

3.86

4.48

*The Apollo 13 mission suffered an explosion on the way to the moon and did not land.

was tacked to the front of the command module like a bicycle
strapped to the front of the family camper. It carried only enough
fuel and supplies for the short trip to the lunar surface, and it was
built to minimize weight and maximize maneuverability.
Th e weaker gravity of the moon made the design of the LM
simpler. Landing on Earth requires reclining couches for the astro-
nauts, but the trip to the lunar surface involved smaller accelerations.
In an early version of the LM, the astronauts sat on what looked like
bicycle seats, but these were later scrapped to save weight. Th e astro-
nauts had no seats at all in the LM, and once they began their
descent and acquired weight, they stood at the controls held by
straps, riding the LM like daredevils on a rocket surfboard.
When it lifted off from the lunar surface, the LM saved
weight by leaving the larger descent rocket and support stage
behind. Only the compartment containing the two astronauts,
their instruments, and their cargo of rocks returned to the com-
mand module orbiting above. Th e astronauts in the LM blasting
up from the lunar surface were again standing at the controls.
Th e rocket engine that lifted them back into orbit around the
moon was not much bigger than a dishwasher.
Th e most complicated part of the trip was the rendezvous
and docking between the tiny remains of the LM and the com-
mand module. Aided by radar systems and computers, the two
astronauts docked with the command module, transferred their
moon rocks, and jettisoned the remains of the LM. Only the
command module returned to Earth.

Th e fi rst human-piloted lunar landing was made on July 20,

1969. While Michael Collins waited in orbit around the moon,
      Neil Armstrong and Edwin Aldrin Jr. took the LM down to the
      surface. Although much of the descent was controlled by com-
      puters, the astronauts had to override a number of computer
      alarms and take control of the LM to avoid a boulder-strewn
      crater bigger than a football fi eld.
      Between July 1969 and December 1972, 12 people reached
      the lunar surface and collected 380 kg (840 lb) of rocks and soil
      (■ Table 21-1). Th e fl ights were carefully planned to visit diff er-
      ent regions and develop a comprehensive understanding of the
      lunar surface.
      Th e fi rst fl ights went to relatively safe landing sites
      (■ Figure 21-4)—Mare Tranquillitatis for Apollo 11 and Oceanus
      Procellarum for Apollo 12. Apollo 13 was aimed at a more com-
      plicated site, but an explosion in an oxygen tank on the way to
      the moon ended all chances of a landing and nearly cost the
      astronauts their lives. Th ey succeeded in using the life support
      in the LM to survive the trip around the moon, and they even-
      tually returned to Earth safely in the crippled command
      module.
      Th e last four Apollo missions, 14 through 17, sampled geo-
      logically important places on the moon. Apollo 14 visited the Fra
      Mauro region, which is covered by ejecta from the impact that
      dug the multiringed basin now fi lled by Mare Imbrium. Apollo
      15 visited the edge of Mare Imbrium at the foot of the Apennine