Life on our home planet may have actually begun on Mars.
That's according to new research by American scientist Steven Benner, presented on August 29 at the Goldschmidt Conference
of geochemists in Florence, Italy.
Benner, of Florida's Westheimer Institute of Science and Technology, argues that the elements boron and molybdenum -- ingredients thought to be crucial for the building blocks of life -- were far more abundant on Mars 3 billion years ago, the time when life began on Earth.
Primitive life, then, could perhaps have emerged on the Red Planet before making its way to Earth on rocks blasted off Mars by impacts or volcanic eruptions.
"The evidence seems to be building that we are actually all Martians; that life started on Mars and came to Earth," Benner said in a press release.
"We very much, in chemistry, want certain kinds of minerals to be present on early Earth to help us do the chemistry we think is important to get life started," he told BBC radio. "The geologists, at least some of them, are telling us that we can't have these chemicals on Earth, we can't have these minerals -- but we could get them on Mars."
The elements boron and molybdenum are thought to be essential starters for life as we know it in helping to protect RNA -- a primitive cousin to DNA -- from the corrosive effects of water.
Without those elements, Benner said, the soupy mix of organic chemicals found on ancient Earth would have formed something more like tar or oil than RNA.
While both of the elements are found on Earth, Benner said it was unclear how they could have spurred life here under ancient conditions. The form of molybdenum needed, he argues, requires more oxygen than was then available in Earth's atmosphere. He said the water on Earth's surface would also have prevented sufficient amounts of boron from forming.
Benner's research, based in part on studies of Martian meteorites, says the conditions on the Red Planet would not have presented those problems.
The idea that primitive life first emerged on Mars and then came to Earth is not a new one, but it has gained prominence in recent years.
This March, a NASA analysis of Martian rock showed that the planet had sulfur, nitrogen, hydrogen, oxygen, and other materials that could have once have supported living microbes.
No proof that life existed on Mars has been found. Whether microbes could have survived the interplanetary trip from Mars to Earth is another question.
If they could have, Benner says, they probably did.
"Meteorites hit Mars all the time and every time a meteorite hits, some pieces of Mars get ejected into the solar system," he told BBC radio. "Some fraction of them find their way to Earth. Many, many kilograms of Mars are coming to Earth every week."
"It's lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life," Benner said in a press release. "If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell."
Not everyone is convinced.
Speaking to NBC News, David Grinspoon, an astrobiologist from the Denver Museum of Nature and Science, said Benner's theory is "plausible," but that it's at least as plausible to stick with the view that life found a way to emerge right here on Earth.
with reporting by BBC and AFP