June 12, 2013
Martian Meteorite Contains Key Building Block Of Early Life
Rebekah Eliason for redOrbit.com - Your Universe Online
A Martian meteorite discovered in Antarctica was found to contain some of the early building blocks of life. The Antarctic Search for Meteorites (ANSMET) team discovered that this meteorite was clearly of Martian origin during its 2009-2010 field season. Contamination from the earth was ruled out and the meteorite was sent to the University of Hawaii at Manoa NASA Astrobiology Institute (UHNAI) for further study.The findings from their research were published on June 6 in the online access journal PLOS ONE.
RNA is a molecule that stores genetic information, and many researchers suspect that it may have been the primary player in the transmission of genetic information before the development of DNA. Our bodies have developed a complex process for synthesizing RNA, but the first RNA molecules must have been formed in a different way.
One of the most difficult aspects of synthesizing RNA is the stable synthesis of ribose, a key component of RNA. Laboratory tests have shown that in the presences of borates, stable ribose compounds form spontaneously. Without borates, however, the chemicals present on the early Earth´s surface could not have synthesized RNA.
“Borates may have been important for the origin of life on Earth because they can stabilize ribose, a crucial component of RNA,” explained James Stephenson, a UHNAI postdoctoral fellow. “In early life RNA is thought to have been the informational precursor to DNA.”
The idea for this specific study came about during an after-work beer conversation between lead authors on the paper Stephenson, an evolutionary biologist, and Lydia Hallis, a cosmochemist who is also a UHNAI postdoctoral fellow.
“Given that boron has been implicated in the emergence of life, I had assumed that it was well characterized in meteorites,” said Stephenson. “Discussing this with Dr. Hallis, I found out that it was barely studied. I was shocked and excited. She then informed me that both the samples and the specialized machinery needed to analyze them were available at UH.”
A team at the W. M. Keck Cosmochemistry Laboratory at UH used an ion microprobe to analyze the veins of Martian clay running through the meteorite. An ion microprobe is a microscope that shoots a beam of highly charged ions at a very small sample. They found that the clay contained ten times more boron than any other meteorite previously measured.
Hallis emphasized the significance of this discovery in regards to the origins of the Earth, explaining that “Earth and Mars used to have much more in common than they do today. Over time, Mars has lost a lot of its atmosphere and surface water, but ancient meteorites preserve delicate clays from wetter periods in Mars´ history. The Martian clay we studied is thought to be up to 700 million years old. The recycling of the Earth´s crust via plate tectonics has left no evidence of clays this old on our planet; hence Martian clays could provide essential information regarding environmental conditions on the early Earth.”
There was no previous evidence of borate enriched clays on the early Earth´s surface, but finding them on Mars implies that they could have been present. These borate-rich clays may represent small pockets that held one of the keys to life´s early molecular building blocks.