Researchers have discovered another clear indicator that life once existed on Mars.
NASA's Curiosity rover has found evidence of boron on the red planet's surface.
It is a key ingredient for life, and scientists say the find is a huge boost in the hunt for life.
Scroll down for video
A selfie of the NASA Curiosity rover at the Murray Buttes in Gale Crater, Mars, a location where boron was found in light-toned calcium sulfate veins, adding to the evidence life once existed on the red planet
RNA (ribonucleic acid) is a nucleic acid present in all modern life, but scientists have long hypothesized an 'RNA World,' where the first proto-life was made of individual RNA strands that both contained genetic information and could copy itself.
A key ingredient of RNA is a sugar called ribose.
But sugars are notoriously unstable; they decompose quickly in water.
The ribose would need another element there to stabilize it.
That's where boron comes in.
When boron is dissolved in water—becoming borate—it will react with the ribose and stabilize it for long enough to make RNA.
'Because borates may play an important role in making RNA—one of the building blocks of life—finding boron on Mars further opens the possibility that life could have once arisen on the planet,' said Patrick Gasda, a postdoctoral researcher at Los Alamos National Laboratory and lead author on the paper, said.
'Borates are one possible bridge from simple organic molecules to RNA. Without RNA, you have no life.
'The presence of boron tells us that, if organics were present on Mars, these chemical reactions could have occurred.'
The paper was published today in the journal Geophysical Research Letters.
The boron found on Mars was discovered in calcium sulfate mineral veins, by Curiosity, meaning the boron was present in Mars groundwater, and provides another indication that some of the groundwater in Gale Cater, where the rover currently is, was habitable, ranging between 0-60 degrees Celsius (32-140 degrees Fahrenheit) and with neutral-to-alkaline pH.
The boron was identified by the rover's laser-shooting ChemCam (Chemistry and