Did life as we know it start on Mars? Are we all Martians? These are the questions some serious scientists are considering.
Speaking at an international conference of geochemists, chemist Steven Benner of the Westheimer Institute of Science and Technology argued Thursday that early Mars provided a more hospitable environment for life to spring up than early Earth.
"The evidence seems to be building that we are actually Martians; that life started on Mars and came to Earth on a rock," he said in a statement.
Scientists generally agree that earliest life took the form of an RNA molecule that could create other RNA molecules based on the same template.
The trouble is, no one has been able to satisfactorily explain how the original "living" bit of RNA formed.
As anyone who has cooked down sugar knows, simply adding energy to organic molecules and then leaving them alone doesn't get you life -- it usually gets you a sticky mixture that Benner describes as "better suited for paving roads than supporting Darwinian evolution."
Another stumbling block for those trying to understand how early life formed is what Benner calls "the water paradox." Earth was covered in water at the time that life was supposed to be forming, and though water is essential to life as we know it, it is also corrosive to biopolymers such as RNA and DNA, which are the building blocks of life, he said.
So, how did life ever get going?
Benner can't say for sure, but he has found evidence that the mineral boron and an oxidized mineral form of the element molybdenum can keep organic material from turning into tar, and may be essential for allowing life to form.
Those two elements were probably not found on early Earth, because there wasn't enough oxygen on our planet at the time and it wasn't dry enough, he said, but they could have been found on early Mars, which did have oxygen and which was more arid.
"It's yet another piece of evidence which makes it more likely life came to Earth on a Martian meteorite, rather than starting on this planet," Benner said in a statement.
[Updated, 9:55 a.m. Aug. 30: In an email to the Los Angeles Times, Chris McKay, a scientist at NASA Ames Research Center, said this part of Benner's hypothesis is not as simple as Benner suggests.
While McKay agrees that molybdenum needs oxygen, and that most of the early Earth did not have oxygen, he believes there were areas of the Earth that did have some oxygen.
"Many years ago I wrote a paper in which we stated: 'The abiotic production of atmospheric oxidants could have provided a mechanism by which locally oxidizing conditions were sustained within spatially confined habitats,'" he wrote."So molybdenum may have been available on the early Earth just locally not globally," he wrote.]
A Mars start for life might also solve the water paradox, he said, because back when life was first forming, Mars had areas of dry land and areas covered by water. Indeed, NASA's Curiosity rover has found evidence of water on Mars and evidence that the planet was once hospitable for life.
So, did Benner's talk provide conclusive evidence that life started on Mars? No. But he did provide evidence to support his theory.
He also adds that although he thinks life could have started on Mars, he's glad it is now thriving on Earth.