Exploring Mars: Are Humans or Robots
Best?
by James Hall, Senior Associate Editor
based on articles written for "Science's Next Wave"
December 4, 2002
Second of Two Parts
"Leaning Left"
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The
Case for Robots
Some scientists disagree with the idea of sending humans to Mars. "Human exploration would be fantastically expensive," Jack Farmer said in a recent phone interview. (Compared to Zubrin's $20-30 billion estimate for a human mission, Mars Odyssey cost NASA $305 million.) "NASA will never send humans to Mars until they know they can do it safely. We have a lot of fundamental work to be done first, on space medicine, weightlessness, the effect of radiation on astronauts traveling to Mars. People need to survive and we shouldn't send them there unless we can bring them back safely. And we have a long way to go to understand Mars itself before we do that."
Astrobiologist Farmer has worked for a decade to develop instruments capable of detecting the places where life may have once existed and might still exist on Mars---within hydrothermal springs like those found in America's Yellowstone National Park.
Some of Earth's oldest organisms---microorganisms called _Archea_---live in calcium carbonate or iron oxide precipitating springs. As chemicals precipitate out of the springwater, they often coat living microorganisms and larger life forms, preserving them like insects in amber. Farmer has found microfossils like these both in existing springs and billion-year-old spring sites on Earth.
"We think there were a lot of hot springs environments on Mars," he says. "On Earth there's hardly a place in these kind of environments where biology is not expressing itself. Given that these springs on Earth are teeming with life, my hunch is that it's a good place to begin looking for life on Mars."
In 1994 Farmer created NASA's current robotic strategy for locating life on Mars: 1) identify likely sites from orbiting spacecraft; 2) send a lander to the best sites to locate fossil-bearing rocks; and 3) send a craft that can gather these samples and return them to Earth for direct study.
In mid--2003, NASA will send the Twin Exploration Rovers mission to Mars. While Mars Odyssey maps likely spots for exploration from orbit, the Twin Rovers will descend to two promising areas and investigate a variety of environments, including what appears to be an ancient hydrothermal spring at Terra Meridiani.
In 2003 the European Space Agency will launch its own search for life on Mars with Mars Express. The Express satellite will orbit Mars and release a lander, Beagle 2, to search for signs of fossilized life on the sedimentary basin of Isidis Planitia.
Based on what's found then, NASA will respond with several robotic missions already scheduled. The 2005 Mar Reconnaissance Orbiter mission will augment Mars Odyssey with instruments capable of examining promising landing sites from orbit. A 2007 "Netlander" mission by the French, Italian, and German space agencies and NASA will examine Mars' atmosphere and interior geology. The 2009 mission will be another lander/rover mission that will follow up on the lessons learned by Twin Rovers and the rest.
Detecting, Protecting Life on Mars
The policy battle over using humans or robots to explore Mars extends to the treatment of any life found there. Zubrin and Lee have been enthusiastic in their desire to set up a human presence quickly. Other NASA scientists have explored the idea of terraforming Mars by increasing the amount of greenhouse gases in Mars' atmosphere.
But Farmer wants to preserve what's there now. "We wouldn't send humans to Mars unless there was a good scientific driver," he says. "Perhaps the discovery of deep aquifer zones inaccessible to robots would cause us to send humans to drill down deep. Even that would pose issues, though. We'd have to know something about that life first."
"If human explorers got a bug, would you let them stay on Mars and die? How would you decontaminate them? There are planetary protection issues here."
Robotic landers are currently sterilized prior to landing on Mars, but it's doubtful that a human mission could avoid contaminating Mars with Earth bacteria and might itself be susceptible to contamination by life forms from Mars.
Conclusions
Humans and robots each offer advantages and disadvantages in exploring Mars. Robots are cheaper to send and safer to use in risky environments, whether the risk is to human beings or indigenous martian life. Humans can get more research done and adapt to unusual situations more easily than robots.
The big question remains the potential compatibility of terrestrial and martian life. If no life exists on Mars, or if it only once existed, then it makes sense to pursue the human exploration of Mars as quickly as possible, even if it means taking some risks. Mars remains the world most accessible and most compatible to humans after Earth itself---that's part of its attraction for us.
But if martian life exists, we ought to study it thoroughly before creating a human presence on Mars that might contaminate Mars' ecosystem---or Earth's. ***
© 2002 James Hall
Pascal Lee is Lead Investigator of the NASA Haughton-Mars Project and a Researcher at NASA Ames Research Center.
Jack Farmer is Chair of the NASA Astrobiology's Institute's Mars Focus Group and Director and Principal Investigator of the Astrobiology Program at Arizona State University.
Robert Zubrin is an aeronautical engineer, President of the Mars Society and of Pioneer Astronautics.
On the Web:
Homepage of the Mars Society, advocacy group for the human exploration of Mars.
COPYRIGHT © 2002 BY THE AMERICAN PARTISAN. All writers retain rights to their work.
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