Scientists Discover How Sun’s Ultraviolet Light Created Life’s Building Blocks on Ancient Mars

Scientists have figured out how ultraviolet light from the Sun helped create the building blocks of life on ancient Mars. This discovery could help us understand if organic material on Mars ever led to the emergence of life on the Red Planet.

NASA’s Curiosity rover found organic material near Mount Sharp, located in the Gale Crater on Mars. (Image Credit: NASA/JPL-Caltech/MSSS).

In New Delhi, researchers explained that carbon has two stable forms: carbon-12 and carbon-13. Carbon-12 has six neutrons and six protons, while carbon-13 has six neutrons and seven protons, making it heavier. About 99% of natural carbon is carbon-12. Around 12 years ago, NASA’s Curiosity rover discovered organic material in sedimentary deposits on Mars, which were formed by ancient flowing water. The ratio of carbon isotopes in this material surprised scientists because it could be due to either life forms or natural geochemical processes.

Twelve years ago, researchers used quantum mechanics simulations to study what happens when an atmosphere rich in carbon dioxide is exposed to strong ultraviolet light from the Sun. Due to a process called photolysis, about 20% of the carbon dioxide splits into oxygen and carbon monoxide. This process works faster on the lighter carbon-12, which is why it is more commonly used by life forms on Earth. The carbon monoxide produced by photolysis has less carbon-13, while the remaining carbon dioxide has more carbon-13 than usual.

Two Samples, 50 Million Kilometers Apart

Researchers identified two different expected patterns in Martian samples. One of these patterns was found last year in a rare Martian meteorite, which was rich in carbon-13. The new study, based on a sample collected on Mars by Curiosity, shows a similar enrichment of carbon-13 in the Martian meteorite sample, along with a depletion of carbon-13 in another Martian sample.

Is There Life on Mars?

A paper describing these findings has been published in Nature Geoscience. One of the study’s authors, Matthew Johnson, said, “Such carbon-based complex molecules are essential for life, the building blocks of life, you might say. So, it’s like the old debate about which came first, the chicken or the egg. We show that the organic material found on Mars was formed through atmospheric photochemical reactions – without life. This is the ’egg,’ a prerequisite for life. It still needs to be shown whether this organic material led to life on Mars. Additionally, because Earth, Mars, and Venus had very similar CO2-rich atmospheres long ago when this photolysis occurred, it can also help us understand how life began on Earth.”