Jan. 9, 2004 — Life may have got its start in a place not entirely unlike Mars' Gusev Crater, say scientists who have discovered an essential ingredient for life in Earth's dry desert lakes.
It turns out that borates — the same family of minerals that brings us 20-Mule Team Borax and Pyrex glass — are able to convert naturally occurring organic chemicals, common throughout the cosmos, into a simple sugar called ribose. That's an essential and long-sought-after step to building RNA and then DNA, on which all life is based.
"We have this image of life emerging from a warm little pond," said organic chemist Steven Benner of the University of Florida in Gainesville.
But it might have started under drier conditions, he says, in places where borate deposits are plentiful, like Death Valley. An article explaining the discovery by Benner, Alonso Ricardo, Matthew Carrigan and Alison Olcott appears in the current issue of the journal Science.
Borates — minerals containing the element boron — form in dry lake beds when eons of mineralized water evaporate and leave thick beds of "evaporite" minerals behind. Borates are particularly easy to carry down to such lakes from surrounding mountains because they dissolve easily in rainwater.
Ribose, for its part, has been suspected as a precursor to life on Earth ever since the 1950s, when Stanley Miller was able to create amino acids, but not ribose, by sending a spark through a soup of simple organic compounds 50 years ago.
Since then the same simple amino-acids Miller made have been discovered ready made in interstellar space, but there didn't seem to be a good way nature could have made ribose from them.
In the late 1990s the ribose problem became so intractable that many researchers started looking for other chemicals for life to get started with, said Benner.
"(This) paper makes it more permissible to include sugar" in the first steps towards life, said Michael Meyer, head of NASA's astrobiology program.
It also points to the possibility that life started in a dry place, rather than a warm pond.
In fact the borate discovery could have implications for Mars' Gusev Crater, where the rover Spirit is now looking for evidence that it is a dry lake bed. If Spirit succeeds, it could mean that Mars too once had at least some of the conditions and ingredients for creating life.
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