Martian clay may have harboured boron – a key component for one of the life’s molecular building blocks – at a time when life was just starting on the Earth,scientists say.
Researchers from the University of Hawaii at Manoa NASA Astrobiology Institute (UHNAI) have discovered high concentrations of boron in a Martian meteorite. When present in its oxidised form (borate),boron may have played a key role in the formation of RNA,one of the building blocks for life.
Researchers found the Martian meteorite used in this study in Antarctica during its 2009-2010 field season. The minerals it contains,as well as its chemical composition,clearly show that it is of Martian origin.
Using the ion microprobe in the WM Keck Cosmochemistry Laboratory at UH,the team was able to analyse veins of Martian clay in the meteorite.
After ruling out contamination from Earth,they determined boron abundances in these clays are over ten times higher than in any previously measured meteorite. “Borates may have been important for the origin of life on Earth because they can stabilise ribose,a crucial component of RNA. In early life RNA is thought to have been the informational precursor to DNA,” said James Stephenson,a UHNAI postdoctoral fellow.
RNA may have been the first molecule to store information and pass it on to the next generation,a mechanism crucial for evolution. Although life has now evolved a sophisticated mechanism to synthesise RNA,the first RNA molecules must have been made without such help. One of the most difficult steps in making RNA non-biologically is the formation of the RNA sugar component,ribose.
Previous laboratory tests have shown that without borate the chemicals available on the early Earth fail to build ribose. However,in the presence of borate,ribose is spontaneously produced and stabilised.
On Earth,borate-enriched salt,sediment and clay deposits are relatively common,but such deposits had never previously been found on an extraterrestrial body. This new research suggests that when life was getting started on Earth,borate could also have been concentrated in deposits on Mars.
“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,” Lydia Hallis,lead author of the study,said.