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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Martian Life: Another Round
18 March 1999 5:30 pm
Scientists involved in the now-suspect discovery of signs of fossilized life on Mars say they have found evidence of past life in a second martian meteorite. But their announcement, made today at the annual Lunar and Planetary Science Conference in Houston, has left colleagues underwhelmed.
Using a powerful scanning electron microscope, geologist David McKay and a team at the Johnson Space Center found rounded or spherical "units" measuring 0.2 to 1 micrometer in a meteorite, discovered in 1911 in Egypt, called Nakhla. The units, they say, resemble small fossilized bacteria. The researchers claim some groupings are reminiscent of dividing bacteria, and argue that their textured surface, the presence of lacy material resembling the mineralized biofilm produced by bacteria, and an occasional fibril-like filament also suggest "possible bacteria in Nakhla."
Researchers have heard all this before. McKay's group made similar "if it looks biological it's probably biological" arguments in 1996 for microfossils in ALH84001, notes microscopist John Bradley of MVA Inc. in Norcross, Georgia. But the group has since retracted those claims, conceding some apparent microfossils were too small ever to have been alive and others were parts of the underlying rock.
"It's very hard to prove" such phenomena are biological, says meteoriticist Horton Newsom of the University of New Mexico, Albuquerque. To see them properly requires a sophisticated scanning electron microscope, but at that fine scale it is impossible to determine composition. So, he says, "they have a long row to hoe to convince people."