Arizona Daily Wildcat January 16, 1998
UA scientists debunk Mars-life theory
NASA scientists stunned the world in August 1996 when they found organic materials in a martian meteorite - evidence they claimed proved that elementary life forms once existed on the red planet.
But new studies by University of Arizona researchers and the Scripps Institute of Oceanography released yesterday found that the rock's organic matter came from the Antarctic ice where the meteorite was found, not from outer space.
The studies, published in today's issue of the journal Science, compared the supposed martian-life leftovers in the meteorite named Alan Hills to organic compounds found on Earth, and concluded them to be identical.
Research scientists Timothy Jull and Warren Beck, of the UA's Accelerator Mass Spectrometer Laboratory, analyzed the carbon isotope levels in the meteorite's organic material. The organic material consists of various carbon compounds, amino acids and mineral deposits.
By measuring Carbon-12, Carbon-13 and Carbon-14 levels in a given sample, scientists are able to determine the origin of material they analyze because the carbon isotope levels on Mars and Earth are vastly different, Jull said.
A lunar rock has a different chemical signature than one from Earth, and a chunk from Mars has a different one than a piece of asteroid. They each have different ratios of carbon isotopes.
Jull said that when his team analyzed the organic matter from Alan Hills, they found the isotopic ratios to be "practically identical" to Earth's organic material.
"We think the sample shows that the organic material in this meteorite is terrestrial contamination," he said.
The scientists also analyzed Carbon-14 levels in the space rock to determine its history. The meteorite formed from a martian volcano, tumbled 16 million years through space, and fell to Earth.
Analysis showed the meteorite landed on Earth 13,000 years ago, Beck said.
"When we did the analysis of the organic carbon in the sample, we found it to be between 5,600 and 11,000 years old," he said. "It is younger than the meteorite's age on Earth."
Meteorite specialist David Kring, a planetary geologist at the UA's Lunar and Planetary Laboratory, said there are a myriad of ways meteorites can be "contaminated" by terrestrial material.
"This material can be deposited by fluids percolating through the rock," Kring said. "This is a common process on Earth."
Rocks in Antarctica can absorb both water and organic matter when they are heated by the sun. A black meteorite sitting on snow and ice will heat up, Kring said, melting a minute bit of the frost around it, then absorbing the water before it re-freezes.
Although the public quickly accepted the meteorite as proof that humans are not alone in the universe, Kring said the scientific community remained skeptical.
Several studies have attacked NASA researchers David McKay and Everett Gibson Jr.'s claim that Alan Hills proved there was life on Mars, Jull said.
"McKay, et. al., made four or five different arguments," Jull said. "Basically, one by one, people are kicking out various portions of the hypothesis. The remaining parts are very shaky at best, so you have to wonder how long this argument will be around."
But Gibson told The Associated Press yesterday he believed the 1996 announcement to be valid.
"Neither paper changes our hypothesis," he said. "It doesn't shake our belief one bit."