Earth lacked vital chemicals for origin of life, claims geochemist. We're all Martians
Evidence is mounting that life on
Earth may have started on Mars. A
leading scientist has claimed that
one particular element believed to
be crucial to the origin of life
would only have been available on
the surface of the red planet.
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."
