Are We All Martians?
Life may have emerge on Mars before arriving on Earth. Recent research supports an idea that the Red Planet was a better place to kick-start biology billions of years ago than the early Earth was.
Professor Steven Benner, a geochemist, has argued that the "seeds" of life probably arrived on Earth in meteorites blasted off Mars by impacts or volcanic eruptions. As evidence, he points to the oxidised mineral form of the element molybdenum, thought to be a catalyst that helped organic molecules develop into the first living structures.
"It's
only when molybdenum becomes highly oxidised that it is able to
influence how early life formed," said Benner, of the Westheimer
Institute for Science and Technology in the US. "This form of
molybdenum
couldn't have been available on Earth at the time life first began,
because three billion years ago, the surface of the Earth had very
little oxygen, but Mars did. "It's yet another piece of evidence which
makes it more likely that life came to Earth on a Martian meteorite,
rather than starting on this planet."All living things are made from organic matter, but simply adding energy to organic molecules will not create life. Instead, left to themselves, organic molecules become something more like tar or asphalt, said Prof Benner. He added:
"Certain
elements seem able to control the propensity of organic materials to
turn to tar, particularly boron and molybdenum, so we believe that
minerals containing both were fundamental to life first starting.
"Analysis of a Martian meteorite recently showed that there was boron on
Mars; we now believe that the oxidised form of molybdenum was there
too."
Another reason why life would have struggled to start on
early Earth was that it was likely to have been covered by water, said
Benner. Water would have prevented sufficient concentrations of boron
forming and is also corrosive to RNA, a DNA cousin believed to be the
first genetic molecule to have appeared. Although there was water on
early Mars, it covered much less of the planet.
"The
evidence seems to be building that we are actually all Martians; that
life started on Mars and came to Earth on a rock," said Benner, speaking
at the Goldschmidt 2013 conference in Florence, Italy. "It's lucky that
we ended up here nevertheless, as certainly Earth has been the better
of the two planets for sustaining life. If our hypothetical Martian
ancestors had remained on Mars, there might not have been a story to
tell."
