Why Mars? Essay by Carl Sagan

By Carl Sagan | September 1996 issue
The Planetary Society

Mars has been a human destination for so long—in both scientific exploration and science fiction—that we might assume that everyone shares the same reasons for wanting to reach the Red Planet. In advancing the cause of Mars exploration, it can be valuable to step back and reassess the reasons for exploring Mars. That is what NASA Administrator Daniel Goldin asked Planetary Society President Carl Sagan to do. Here are his conclusions. — Charlene M. Anderson

• Mars is the nearest planet that astronauts can explore.

• About 4 billion years ago, Mars seems to have had an Earth-like climate, with rivers, lakes and perhaps even oceans. (This was at a time when the Sun was 25 percent dimmer than it is today.) Something unknown converted an Earth-like world to a deep ice-age planet. Perhaps we, who are perturbing our planetary environment, should understand what happened to the climate of Mars.

• Mars has a planet-wide ozone hole. Ultraviolet light from the Sun strikes its surface unimpeded. This is thought to be the reason that not even organic molecules were found by the Viking 1 and 2 landers. The study of Mars, therefore, helps us understand what the extreme consequences of ozone layer depletion on Earth might be.

• In exactly the same epoch that Mars was warm and wet, life arose on Earth. Is it plausible that on two nearby planets with very similar environments, life arose on one and not the other? The search for morphological or chemical fossils of past life on Mars is one of the most exciting goals of planetary exploration. If found, it might indicate that life arises quickly on all planets in the universe where the conditions are right.

• As the martian climate degraded, life if any would have retreated to the last habitable regions, surface or subsurface. If there are martian “oases” today, could life on Mars—despite the negative results from Viking—be waiting to be found? If found, it might show what kinds of life—fundamentally different from life on Earth—are possible.

• Mars is an ideal arena for international cooperation in space exploration. Despite fiscal and infrastructure problems, the Russian space agency appears on track for the Mars ’96 launch and recently approved a Mars 2001 mission plan. Mars Together remains a high-level government initiative. A Japanese Mars orbiter is scheduled to be launched in 1998. European national agencies (notably the French and German) have significant roles in current Mars missions and plan for future ones as well. The United States has an opportunity to play a key role in a new kind of coordinated scientific exploration of another planet through international combined operations.

• Mars exploration is a potential testing ground for a range of new technologies—including aerobraking and the use of martian resources to generate oxidizer and fuel for the return journey (and water and oxygen for eventual human missions). It is also an ideal testing ground for remote rover and returned-sample missions, as well as long time-delay telepresence and virtual reality.

• Because of the historic romance of the general public with Mars (consider even today the associations of the word “martian”), the exploration of Mars has a public resonance and support that probably no other goal of the space program can claim.

• Although the SNC meteorites (named for the places on Earth where they were found—Shergotty, Nakhla and Chassigny) provide samples of a few (unknown) locales on Mars, they cannot provide a fair sample of this heterogenous planet.

• The goal of eventual human missions to Mars provides a coherent justification for the international space station—especially if used for studies of long duration stays (one to two years) of humans in space.

• In the long run, Mars is the prime site for self-sustaining communities on other worlds.

• On a longer term, Mars is the most readily terraformed world in the solar system.

• Mars helps to provide a hopeful dream of a positive future for our children and grandchildren. It can vividly illuminate American discipline, imagination and persistence, and an opportunity to help steer our planet out of the lingering shadows of the Cold War.

Carl Sagan on the Exploration of Mars – The Planetary Society

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