The debate on the question of life on Mars goes back to NASA's Viking 1 that landed on Mars in 1976. Though it is considered that the surface of Mars is hostile to life, scientists are not foreclosing possibility of microbial forms of life on the planet because we know that life is found in relatively harsh environments on Earth such as the Antarctic and the Atacama desert in Chile.
Scientists had concluded from information sent back to Earth by Viking that there were no signs of life on Mars. Methyl chloride and dichloromethane molecules detected by Viking were believed to be contamination from the vehicle itself. However, one of NASA's scientists Gilbert Levin, insisted that his tests found evidence of metabolism. Scientists, because of the controversies, have been awaiting opportunity for re-evaluation of the evidence from the Viking landings. Maine Sunday Telegraph
quotes NASA's director of planetary sciences James Green, commenting on the potential significance of NASA's latest Mars mission, the Mars Science Laboratory Curiosity mission:
"With this mission, we really enter the modern era of astrobiology, the search for life beyond Earth...And we have the technology and know-how to make some extraordinary discoveries."
This latest mission, if it succeeds, will be NASA's seventh successful touchdown mission to Mars. U.S. enjoys the distinction of being the only country in the world that has landed a working craft on Mars. Efforts by the Soviet Union and later the Russian Federation have all failed. NASA's new Mars rover, Curiosity, is the cynosure of the the latest Mars mission. It is the most sophisticated surface vehicle ever. The plan, according to Maine Sunday Telegraph
, is to land the rover on Mars using a multi-stage landing system. The one-ton rover will be landed on the surface of Mars by a device similar to a crane. The rover will be carrying some of the most sophisticated equipment ever deployed in any science-lab mission.
The rover is expected to land near the base of a 3 mile high layered mountain inside the Gale Crater. It will be climbing up the mountain, investigating its layers, looking for evidence in the layers of past conditions on Mars favorable for development of life, specifically microbial life. Curiosity will also be for searching for evidence that water once ran in the Gale Crater mountain.
The question whether there is water on Mars has interested scientists for decades. According to John Grotzinger, project scientist from the Mars Science Laboratory at the California Institute of Technology, Pasadena,
"The portion of the crater where Curiosity will land has an alluvial fan likely formed by water-carried sediments...Layers at the base of the mountain contain clays and sulfates, both known to form in water."
The disproportionate amount of interest in whether water has ever existed on Mars comes, of course, from the fact that scientists generally believe the water is essential for development of life. Some scientists claim evidence that Mars was once warm enough to sustain running liquid water on its surface. They point to features on the surface of the planet which they believe could have been formed by running water. Some scientists even argue that water still runs on the planet. According to Space.com
, dark narrow lines on Martian slopes have been interpreted as evidence of saltwater running seasonally.
But Curiosity will not only be looking for evidence of water on Mars, it will also be looking for signs of life independent of presence of water given recent evidence of alternative possibilities to water, such as methane gas, for supporting life. The European Space Agency's Mars Express spacecraft discovered Methane in the Mars atmosphere in 2003. Curiosity will be looking to answer the question of the origin of Methane in Mars atmosphere. This is an important question for Curiosity to answer because Methane is associated with life on Earth, though there are other means of producing Methane in a planetary atmosphere besides life processes. Volcanic activity, for instance, may produce atmospheric methane.
Maine Sunday Telegraph
reports Curiosity will be carrying instruments that can test whether carbon in the Martian soil has isotopic properties associated with life on Earth.
According to Pamela Conrad of NASA's Goddard Space Flight Center, Curiosity will be conducting comprehensive search for evidence of life. She says:
"We want to know everything we can about the minerals, the carbon-based compounds, the temperatures, the chemistry of the micro-environments we look at."
Finally, scientists will be seeking to resolve the controversy that first arose in the 1980s over suggestions that life on Earth might have originated from Mars.
The most recent relevant claim comes from NASA Astrobiologist Richard Hoover of Marshall Space Flight Center in Huntsville Ala.. He claimed he had found evidence of alien life on a meteorite that might have originated from Mars. Hoover used a scanning electron microscope to analyze slices of the carbonaceous meteorites. He concluded from his analysis of the structure of filaments that the meteorites bore fossils of microbes, specifically cyanobacteria or blue-green algae. Space.com
reports that Hoover said,
"...the size, structure, detailed morphological characteristics and chemical compositions of the meteorite filaments are not consistent with known species of minerals."
Earlier in 1996, some researchers had claimed evidence for fossilized microbial life in a Mars meteorite called Allan Hills 84001 (ALH 84001). Lead Researcher David McKay of NASA's Johnson Space Center, published the findings in the journal Science
. But other scientists have questioned the claim. Space.com
reports Planetary geologist Victoria Hamilton of the Southwest Research Institute in Boulder, Colo., expressed skepticism shared by many of her colleagues:
"...claims for evidence of microfossils in ALH 84001 remain controversial at best, despite more than a decade of dedicated research by many groups and dozens of scientific papers on the subject..."
reports that in spite of skepticism being widely expressed about the possibility of life from space, evidence has existed since the 1980s, from analysis of trace gases within meteorites found on Earth, that some had indeed originated from Mars. Recent evidence, according to Space.com
, shows, for instance, that the southern half of the Martian surface received massive space rock impacts strong enough to eject rocks from the surface of Mars into space and to Earth. According to Brett Gladman, astronomer at the Observatoire de la Cote D'Azur, France,
"It's surprisingly easy to get material from Mars to Earth...If you launch stuff off Mars, there aren't a lot of other places to go."
Other researchers such as Curt Mileikowsky
of the Royal Institute of Technology in Stockholm, determined that about 50 billion Martian rocks landed on Earth during the first 500 million years of the solar system. The team of researchers estimated that the flow of meteorites from Earth to Mars early in the evolution of the solar system was only about one fiftieth the flow from Mars to Earth.
The special implication of these information is that if life had existed on Mars early in the history of the solar system, Earth could have been contaminated by simple life forms from Mars several times in the past. The suggestion that life on Earth might have originated in Mars would appear to be further supported by evidence that certain types of Earth bacteria may be able to survive the conditions likely to be encountered when rocks ejected from a planet travel through space and impact on another.
Curiosity rover only need deliver evidence that microbial life had existed on Mars in the past to give credence to the claim by some astrobiologists that life on Earth might have originated on Mars.