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Beyond the Moon To Mars Part III - What's the Next Step?

Posted on: Thursday, 6 May 2004, 06:00 CDT

Interview with Dr. Andrew Chaikin

The fourth and final installment of this multi-part series, 'Can Humans Get To Mars?', considers what we have learned about the moon from robotic and remote sensing.

Astrobiology Magazine -- On December 11, 1972 - thirty-one years ago- the astronauts of Apollo 17 eased their Lunar Module into a landing, beginning the last human excursion to the Moon.

Three days later, Eugene Cernan and Harrison Schmitt blasted off from the lunar surface to rejoin crewmate Ronald Evans in the Command/Service Module. The crew circled the Moon for another forty-eight hours or so, fired the spacecraft's thruster, and left the Moon behind for the next three decades.

During their brief stay on the Moon, Commander Cernan and geologist Schmitt crisscrossed the local terrain in their Lunar Rover, conducting a variety of experiments and gathering Moon rocks to bring home. Thirty year later, there's a resurgence of interest in returning to the Moon.

The Moon is believed to play an important role in Earth's habitability . Because the Moon helps stabilize the tilt of the Earth's rotation, it prevents the Earth from wobbling between climatic extremes. Without the Moon, seasonal shifts would likely outpace even the most adaptable forms of life.

In addition, because our moon is lifeless, it is one of the most appealing places to look for the preserved records of life elsewhere. At least according to recent estimates for the amount of ejected rocks that might survive there, the Moon may hold clues from the early history of Mars, Venus and Earth.

Unfortunately, the very early geological history of Earth has been nearly completely obliterated by the actions of tectonics, weathering, and biology; on our home planet the earliest rock records date back about 3.8 billion years but no further.

Scientists John Armstrong and Lloyd Wells of the University of Washington in Seattle and Guillermo Gonzalez of Iowa State University argue for resuming human missions to the Moon to collect not Moon rocks, but Earth rocks.

Early in Earth's history, a rain of comets known as the Late Heavy Bombardment may have blasted bits of Earth's surface into space; some of the material might now lie strewn across the lunar surface. The rocks might even contain fossil evidence of the earliest life on Earth life, the researchers say.

Scientist Kevin Zahnle of NASA Ames Research Center adds that studying the existing collection of Moon rocks returned by Apollo 17 and the five earlier lunar landings could help test techniques for searching for Earth rocks on the Moon. And NASA astrobiologist David McKay of Johnson Space Center has remarked that, to his knowledge, no one has searched the collection of Moon rocks for Earth minerals.

The Moon, however, still retains some of the earliest records of the formation of the Earth-Moon system. Leading models suggest a very early origin of the Moon as a result of the collision of a Mars-sized body with the newly formed Earth.

Samples from the Apollo and Luna programs elucidated some of this history, but the nature of these samples, limited to equatorial regions of the lunar near side, leaves many key questions unanswered.

The Moon's South Pole-Aitken Basin, one of the largest impact structures known within the solar system, exposes material from deep within the crust and possibly even the upper mantle that was excavated by the impact. In addition, the floor of this basin probably retains impact melt rocks created by the giant impact.

Apollo experience shows that such melt rocks provide insight into the average composition of the basin, and that by dating such samples we can infer the age of the basin itself. This will help to resolve questions that are raised by the observed cratering record of the lunar highlands, with important implications for the early history of the Moon and all of the terrestrial planets, including Earth.

Analysis of ancient lunar material will thus provide critical insights into the processes that occurred on Earth and the other terrestrial planets during their early history.

For more than 40 years, the Moon has been visited by automated space probes and by nine manned expeditions, six of which landed on its surface.

Most recently on the night of September 27th, 2003, Europe's lunar probe called SMART-1 launched on a technology demonstration mission to the moon. Much remains to be learnt about our closest neighbour, and SMART-1's payload will conduct observations never performed before in such detail.

Astronaut Eugene Cernan salutes the American flag during the final Moon mission, Apollo 17. Credit: NASA

Artist's rendition of the SMART-1 Moon Mission. Credit: ESA

Artist's rendition of humans exploring the Moon. Credit: NASA

The Advanced/Moon Micro-Imaging Experiment (AMIE) miniaturized CCD camera will provide high-resolution and high-sensitivity imagery of the surface, even in poorly lit polar areas. The highly compact infrared spectrometer will map lunar materials and look for water and carbon dioxide ice in permanently shadowed craters.

Although the recent history of lunar missions has been dominated by robotic probes, revisions to the future timeline may be forthcoming if the Presidential Commission on Moon to Mars and Beyond continues to develop towards fruition. As Chaikin noted in his lecture series on the subject, it remains a remarkable realization however, that it was 31 years ago that the last human left the moon.

Recent Lunar Timelines

1990

- Japanese Hiten, Lunar Flyby and Orbiter

1994

- Michael Rampino and Richard Strothers propose Earth could be periodically struck by comets dislodged from orbits when the solar system passes through galactic plane

- US Dept. Defense/NASA Clementine mission, Lunar Orbiter/Attempted Asteroid Flyby

1997

- First commercial lunar mission, AsiaSat 3/HGS-1 , Lunar Flyby

1998

- Lunar Prospector launches and enters lunar orbit

1999

- Lunar Prospector tries to detect water on the Moon (polar impact)

2001

- Lunar soil samples and computer models by Robin Canup and Erik Asphaug support impact origin of moon

2003

- SMART 1, to launch lunar orbiter and test solar-powered ion drive for deep space missions

2004

- Japanese Lunar-A, Lunar Mapping Orbiter and Penetrator, to fire two bullets 3 meters into the lunar soil near Apollo 12 and 14 sites

2006

- Japanese SELENE Lunar Orbiter and Lander, to probe the origin and evolution of the moon

Beyond the Moon To Mars Part I - Hemorrhaging from the Fingertips

Beyond the Moon To Mars Part II - Going Mobile

Beyond the Moon To Mars Part III - Man or Machine?

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On the Net:

Dr. Andrew Chaikin Website

Mars Exploration Rover Mission

NASA

Cornell University Athena

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