WHY SHOULD WE EXPLORE MARS?

Mars is the most Earth-like of the five terrestrial planets and will be the first other planet humans will visit. Why? The Moon and Mercury are dry airless bodies. Venus has suffered a runaway greenhouse effect, developing a very dense carbon dioxide atmosphere that has resulted in the escape of all its water and uninhabitable surface temperatures of 750K. Mars, on the other hand, has everything necessary to support life, including an atmosphere with polar caps and large amounts of water. Mars is, in fact, the only other terrestrial planet with abundant water (and liquid water is absolutely required for life as we know it). So eventually humans will visit Mars not only because it is the only other planet with reasonable surface conditions, but for the potential of what it might become in the much more distant future - another home for people.

Mars is also the only other place were we can begin to address the question - "Are we alone in the universe?" Is life a cosmic accident or does life develop anywhere the proper environmental conditions are met? A number of studies have shown that the likelihood of humans hearing from possible advanced civilizations in other solar systems is extremely remote given the enormous distances (and long time delays) involved. Mars is our neighbor and, unlike any other planet in our solar system, substantial evidence indicates that early environmental conditions may have been similar to those on the young Earth. On Earth, evidence for life can be found in some of the oldest rocks, dating from the end of terminal bombardment around 4 billion years ago. Surfaces on Mars that are of this age show remains of ancient lakes, implying that liquid water was in equilibrium with the atmosphere at that time and that the climate was both wetter and substantially warmer. If this is true, then we can learn, through further exploration, whether life did develop on Mars, or if not why not. If life did develop on Mars what has happened to it, given that Viking found no evidence present-day life at the two landing sites? We could even begin to explore whether life that began early on could still survive in some specialized niches, such as hydrothermal systems near volcanoes.

The Arctic and Antarctic Ozone Holes. (P-42210, P-42211)

Finally, exploring Mars provides a way of better understanding significant issues that face humankind in the future, namely the factors involved in natural changes in a planet's climate. On the Earth, one of the most important questions now being studied is whether or not humans are contributing to global warming (if it is occurring via industrial emissions). We do not know if we are, or if these changes could produce negative environmental changes such as sea level rise due to melting of the ice cap (most of the world's largest cities are at elevations very close to sea level). Mars, on the other hand, provides a natural laboratory for studying climatic changes on a variety of time scales. If Mars was warmer and wetter with a thicker atmosphere in the past, why did it change?

In addition, layered deposits near the martian polar caps suggest climatic fluctuations on a shorter time scale. If we can learn the important factors controlling climatic changes on another planet, we may be better capable of understanding the consequences of human-influenced changes on Earth. Lastly, Mars is an excellent laboratory to engage in such a study, given that its geologic activity has produced rocks on the surface of virtually all ages to study. Unlike the overactive Earth and Venus, where most of the surface is covered by young rocks, and the inactive Mercury and Moon, where only ancient rocks are present, Mars has had an intermediate level of geological activity, which has produced rocks on the surface that preserve the entire history of the solar system. Sedimentary rocks preserved on the surface contain a record of the environmental conditions in which they formed and thus any climatic changes that have occurred through time.

Mars

Calvin J. Hamilton; last update: February 3, 1995