All of the bases in DNA and RNA have now been found in meteorites

The origins of our planet have been debated for many years since scientists first proposed the “big bang” theory. However, a discovery from April last year further moves this theory into the spotlight. Scientists have found three meteorites that contain the molecular building blocks of DNA and RNA that started the formation of the earliest lifeforms on Earth some four billion years ago. Whether or not these DNA components are extraterrestrial or not, however, is now being debated among scientists.

Scientists Discovery Building Blocks Of Human Origins In Meteorites

Scientists have now discovered that all five nucleobases found in DNA and RNA are also found in meteorite fragments. They discovered this when scientists placed asteroid grains into a meteorite tea and heated it, allowing the nucleobases to combine with phosphates. This combination allowed them to form the informational units of DNA and RNA: cytosine, adenine, guanine, and thymine. This new study marks the first time all five nucleobases have been found together outside of Earth. These bases combine with other compounds to form the genetic code used to create all forms of life on Earth. (1)

Scientists believe this could be due to meteorites carrying components necessary for life with them as they travel through space. As these meteorites crash into planets, they could help create genetic code from their nucleobases as seen in this new study. The discovery of these bases being found in meteorites is a huge advancement for scientists studying the origins of life on Earth and other planets. (2)

The Meteorites May Hold The Key To Human Origins 

Researchers have detected several organic and inorganic compounds that are similar to the soil abundances measured on Earth. The three meteorites they studied contained the four bases found in DNA and RNA and a few amino acids. These measured meteorite values were compared to those of the surrounding soil and rocks. The researchers found that all DNA and RNA bases were present at much higher concentrations than expected. Cytosine was even detected at 10-100 times what was typically measured.

They also found that the heterocyclic nitrogen molecules in meteorites are similar to those found on Earth, but the ratios of these molecules suggest that they were formed in an extraterrestrial environment. While nitrogen-based analogs of several DNA and RNA bases have been identified in Murchison meteorite extracts, the same molecules were also detected in soil extracts contained on Murchison soil. This includes purine, thymine, and uracil based analogs. 

The distributions of these related molecules suggest different synthesis pathways for terrestrial versus extraterrestrial environments. This implies that either the meteorite or its parent body could have been a source of nitrogen heterocyclic molecules on our planet, including DNA and RNA bases. The recent findings help to support earlier theories that some components necessary for life may have come from space and initiated life on Earth.

Extraterrestrial or From Earth?

Analytical chemist, astrobiologist, and associate professor at Boise State University Michael Callahan says that while the findings are exciting, they don’t necessarily mean that the DNA components are of extraterrestrial origin. Though he was not involved in the study, he says that it is possible that some of this DNA might have ended up in the meteorites after they landed on Earth. To rule out this possibility, he says more studies are needed.

There is some evidence in this study; however, that suggests that the DNA did come from outer space. Scientists detected other types of nucleobases that were surrounded by meteorites. These space rocks had three pyrimidines, one of which was a pyrimidine called uracil. Testing the soil surrounding these meteorites identified a purine, adenine, and another pyrimidine which sheds new light on the origination of life on Earth. 

The discovery of guanine in the Murchison meteorite suggests that these nucleobases came from space, not from a young Earth. Not only does this discovery shed new light on the origin of life on Earth but also suggests that these components were present in space rocks prior to life being formed. This sheds further evidence to support theories that some components necessary for life may have come from space and initiated life on our planet.

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