Mars probes embody
mankind’s grandest quest
Early on Christmas Day, a European Space Agency (ESA) spacecraft named Beagle 2 descended to the surface of Mars. It was scheduled to bounce to a stop after a 60 million-mile trip that lasted nearly seven months. An important aspect of the Beagle 2 lander's mission, part of a larger ESA project known as Mars Express, is to search for water below the surface sands of Mars and to detect certain life signatures in the ongoing quest to determine whether Earth is alone in having the self-replicating, metabolizing chemical and physical structures that we know as life.
Beagle 2 was the first lander since NASA's two Viking probes in the 1970s to look specifically for evidence of past or present life. No other Mars probe planned so far is making exobiology so central to its mission, although two NASA craft, Spirit and Opportunity, are slated to explore the surface this month.
Beagle 2 was designed to use the thin atmosphere of Mars to slow from more than 12,000 mph before inflating three balloonlike bubbles to cushion its fall and slow it further after impacting the surface. Although no signal was received from the lander after descent, the Mars Express orbiter, mother ship of Europe's first mission to the red planet, is in a stable and precise orbit around Mars and functioning as planned. Even without the lander, the most essential part of the European Mars mission is performing very well, according to the ESA. It is hoped that as the orbit of the Mars Express orbiter is adjusted, communications can be established and the fate of the lander will be known.
Beagle 2 is named after the ship that carried Charles Darwin on his famous voyage of discovery in 1831-32. Darwin, a keen observer with a logical mind, was the naturalist on the voyage that had a primary mission to map the coastline of southern South America. Darwin observed the variety and similarity of life forms that eventually led to the theory of biological evolution. Beagle 2 is on a similar voyage of discovery, hoping to find signs that our closest planetary neighbor might have harbored life at some time, past or present.
The conclusions that Darwin drew from the astute observations he made during the voyage of the Beagle ushered in a new age in the science of biology and launched a paradigm that has clarified our understanding of the connectedness of life on Earth, and has generated equally as much controversy among those who refuse to consider it because it appears at cursory glance to conflict with religious beliefs. That notwithstanding, Darwin's ideas have affected our perceptions of ourselves and our place in nature as no other scientific ideas have.
Not only did they place mankind smack in the middle of nature rather than separate from it, they provided yet another blow to the egocentric viewpoint that we live in a world created especially for us, a transformation that began with the overturn of geocentrism that started with Copernicus in the 16th century and culminated with the work of Galileo and Newton in the following century.
Whatever the mechanisms underlying evolution, the body of geological, zoological and molecular evidence is overwhelming that there has been an ongoing change in life on Earth from simple to more complex forms over 4 billion years. It is important to remember when contemplating the nature and importance of the search for life on other worlds that all life forms on Earth today are remarkably similar to one another and to past life on Earth. There is no reason to believe that even the most ancient life on Earth relied upon a different set of chemical and biological parameters than those that are found in the immense variety of forms present today.
Life as we know it, and the only kind we know of, is based on the chemistry of carbon. The isotope known as carbon-12 is slightly more reactive than carbon-13 because it has slightly less mass. The presence of six neutrons in the nucleus of atoms of carbon-12 compared with seven in the heavier carbon-13 means that carbon-12 is favorably extracted from the environment, leading to a slight but measurable enrichment of carbon-12 in biological compounds. There are no other known processes that produce this kind of enrichment, therefore any enrichment of carbon-12 indicates some sort of biological process. This is one of the biological signatures the Beagle 2 will seek on Mars as an indicator of past or present life.
Another chemical signature Beagle 2 is designed to detect is the presence of methane in the atmosphere of Mars. Methane is a highly reactive gas that comes from sources such as termites, cows and swamps on Earth; on Mars it might come from extreme-loving microbes. Methane could not survive for long periods in the Martian atmosphere where there is no ozone to block the sun's ultraviolet radiation that on Earth quickly dissociates methane molecules in the atmosphere. According to NASA's Everett Gibson, the interdisciplinary scientist for the Mars Express/Beagle 2 mission, if Beagle 2 can find methane, "it will go a long way to answering that key question, Are biological processes operating on Mars?"
On Earth, multicellular life forms are supported by a web of energy production and nutrient cycles that include myriad organisms. On Mars the conditions necessary to support the ecology of complex multicellular forms simply do not exist. If there is life today, it is most likely simple, single-celled and existing below the dry surface where daily and yearly temperature variations are not as extreme and where water might be available to support the chemical reactions necessary to transform, store and metabolize the sun's radiant energy.
Improbable as it may be to find it, the search for life goes on because current theories about the origin of the sun and planets indicate that the conditions that were present on Earth in the first few billion years or so might have been present on Mars and Venus as well. The physical environment on Venus is now known to be too harsh to support life and is likely to have erased traces of ancient life even if it existed there.
Being that there is no way to calculate the odds that life exists now or ever existed on Mars or anywhere else in the immediate vicinity of Earth, it is not unreasonable to ask why we should expend the resources to send spacecraft out there when there is a strong possibility that they will fail to find evidence of life, especially when there are so many problems here on Earth that, at first glance, might seem to be more pressing.
Mankind has always populated by explorers who are interested in expanding our horizons, and exploration has always been beneficial in the long run, even though that same exploratory urge has also created ethnic and political conflicts like the ones that dominate the news today. Despite that, the poorest and most retched among us benefit from the technology and innovation that stem, however indirectly, from those explorations.
From the beginnings of our species on the plains of Africa 8 million years ago, people have spread out seeking new lands, new resources and new experiences. This exploratory urge is a part of the human psyche and is part of the reason we want to reach for the stars but not the whole reason. Pure curiosity and thirst for knowledge have been our evolutionary forte and derive from the same roots as the exploratory urge.
Beyond that is the deeply rooted spiritual need to know who we are and our place in the universe that keeps growing with new discoveries, and which science has made no less awesome than it was for our most ancient ancestors who stared at the stars with curiosity and wonderment. The same need to know that drives our science and our quest for knowledge of the physical world is also behind our spiritual quest to know our place in it.
To appreciate this, ask yourself what it would mean to find that life on Earth is not unique, even if it is only single-celled microbes. Consider the wealth of literature that has considered this. Look at the cultural shock when Pacific islanders found that they were not alone, and not merely the effects of the invasion of Westerners. Look at what the knowledge that Earth was not the physical center of the universe did when it ushered in a new age of enlightenment in the 16th and 17th centuries. Look at how our place in the universe changed at the mere suggestion by Darwin that we are not a special creation, but rather the most glorious and remarkable result of a 4 billion-year evolution that began with a single cell, or a special chemical reaction, which we may never know the nature of with certainty.
The discovery of life on Mars or elsewhere would change our perception of ourselves in a way that nothing else in history has done, regardless of its complexity or familiarity. Beyond that, it would confirm or deny the unity of life by showing us whether we share with extraterrestrial life the same genetic code and metabolic chemistry.
But even beyond that, it could help us to understand our own beginnings, especially if Mars has not been able to produce life forms beyond those that might have developed eons ago when conditions were more similar on the two planets.
Even finding no evidence of life on Mars, or elsewhere in the solar neighborhood, will only deepen the mystery of our own existence. If it turns out that we are alone, which of course we can never prove beyond doubt, it would only make us even more curious about our own existence.
Hopefully, it will not make us more arrogant.
Richard Brill, a professor at Honolulu Community College, teaches earth and physical science and investigates life and the universe. E-mail questions and comments to firstname.lastname@example.org
BACK TO TOP
in new Mars rovers
PASADENA, Calif. >> The twin rovers that NASA hopes to land on Mars this month may resemble the plucky Sojourner robot that was the star of 1997's Pathfinder mission, but looks are deceiving.
The lineage of the new rovers, Spirit and Opportunity, is unmistakable. Each one has six aluminum wheels, a boxy body coated with gold and a flat expanse of glossy solar panels -- just like Sojourner.
But the new rovers weigh 384 pounds apiece compared with petite Sojourner's 24 pounds, like a pair of golf carts next to a microwave oven.
"They are, in some ways, grown-up versions of Sojourner," said Andrew Mishkin, of the National Aeronautics and Space Administration's Jet Propulsion Laboratory.
NASA calls Spirit and Opportunity the most sophisticated robots ever sent to another planet.
If successful, they should roam farther and accomplish more during their 90-day missions than Sojourner did during its three months of activity.
"They are certainly extremely complicated, extremely powerful and extremely sophisticated robots," said Steve Squyres, the principal scientist on the $820 million double mission.
Spirit landed on Mars yesterday. Opportunity should follow on Jan. 24, landing on the opposite side of the planet. They are supposed to be in operation on the Mars surface for 90 days.
Previous NASA spacecraft -- the twin Viking landers in 1976 and Pathfinder in 1997 -- have visited just three locations on Mars.
Doubling up boosts the odds of success. About two-thirds of all missions sent to the surface of Mars have failed. The latest may be the British Beagle 2 lander, which has not been heard from since it was to have set down on Mars in late December.
The Mars Exploration Rovers are relying on the same air bag system that the Pathfinder lander used to cushion its landing on the rocky surface of Mars. NASA's failed Polar Lander, which crashed in 1999, did not.
Unlike Pathfinder, the landers that deliver Spirit and Opportunity to the surface will cease to play any role once they are left behind by the two rovers.
Spirit and Opportunity were designed to carry all the communications and camera equipment that was split between Sojourner and its Pathfinder lander.
"We have effectively merged the capability of the Pathfinder lander and the Sojourner rover into one larger rover," said Mishkin, who heads the team that develops the instructions that will be sent to the two robots each day.
"In a sense, we have taken the Pathfinder lander and put it on wheels. If you think about that, you'd say, 'How did they make it so small?'" he added.
NASA expects it will take each rover nine days of preparation before it is ready to trundle off.
Sojourner traveled a grand total of 328 feet on the Martian surface, but NASA expects Spirit and Opportunity to cover up to 65 feet a day, or as much as 1,650 feet, depending on terrain.
The mission was designed to examine rocks and soil for evidence the planet once may have been a wetter place hospitable to life, and mission members boast that each rover should reconnoiter its surroundings nearly as skillfully as would a human rockhound.
"It's a robotic geologist doing the science -- the same things we would be doing if we could get ourselves there," said Jim Bell, a Cornell University astronomer and member of the mission's science team.
Sojourner, more technology demonstration than geology whiz, carried a single primary science instrument. Spirit and Opportunity each carry a version of the same instrument, plus a half-dozen more.
"If successful, Spirit and Opportunity will help humans take a giant leap forward in their understanding of Mars' potential as a site for past or current life," said Ed Weiler, NASA's associate administrator for space science.
Spirit was launched from Cape Canaveral, Fla., in June, and Opportunity took off in July. During their flights, adjustments were made in their trajectories to ensure that the landers carrying the two rovers entered the Martian atmosphere on course.
Richard Brill picks up
where your high school science teacher left off. He is a professor of science
at Honolulu Community College, where he teaches earth and physical
science and investigates life and the universe.
He can be contacted by e-mail at email@example.com