Does an out-of-this-world sugar discovery help solve one of science’s great mysteries?
Sugars, especially ribose and deoxyribose (5-carbon sugars), are indispensable molecules for life. Without ribose and deoxyribose, RNA and DNA molecules cannot be assembled. Ribose and deoxyribose are the glues that allow nucleobase molecules to be joined together to make RNA and DNA, which are responsible for storing and reading genetic information that underpins all life.
Researchers intent on finding a naturalistic pathway for the origin of life have long recognized that the apparent lack of a natural nonbiological source of ribose and deoxyribose stood as a fundamental barrier to their goal. Hence, for over five decades they have been scouring the earth and the universe in a quest to find the elusive sugars.
Realizing that conditions on Earth at the time that life first originated ruled out any naturalistic source of ribose and deoxyribose, origin-of-life researchers looked to the heavens. At the beginning of the 1970s they determined that their best chances of success lay in dense molecular clouds, comets, and meteorites. Ultimately, they’ve focused on dense molecular clouds since these interstellar clouds are the source of comets and meteorites.
Interstellar molecular clouds, especially Sagittarius B2 (the very large and dense cloud near the center of our galaxy), has yielded discoveries of an immense array of carbonaceous molecules. To date, nearly 200 different molecules have been discovered in the interstellar medium. Of these, 60 are complex organic molecules consisting of six or more atoms.1 The existence of all these molecules implies that chemical reactions must be operating within dense molecular clouds to produce both ribose and deoxyribose. However, the presence of these molecules also implies that chemical reactions must be operating to destroy most, if not nearly all, the ribose and deoxyribose that is manufactured. Consequently, the expected abundance of ribose and deoxyribose in dense molecular clouds, at best, is only a few parts per billion. Currently, astronomers lack the instruments to detect ribose and deoxyribose at such low abundance levels, though they have detected glycolaldehyde (2-carbon sugar) and glyceraldehyde (3-carbon sugar) in interstellar ice analogues in laboratory conditions.2
Discovery of Extraterrestrial Ribose
Comets, asteroids, and meteoroids, which arise from molecular clouds, possess higher concentrations of carbonaceous molecules. Hence, astronomers have been diligently searching for ribose and deoxyribose in these sources. Recently, they developed the instrumentation to detect complex organic molecules in meteorites at abundance levels as low as 0.5 parts per billion. With this new technology they finally detected ribose, a building block of life, in two primitive meteorites: NWA 801 and Murchison.3
In the NWA 801 meteorite ribose was found at 4.5 parts per billion. In the Murchison meteorite ribose was found at 25 parts per billion. Ribose was not found in any of the other meteorites studied by the team. Deoxyribose was not found in any of the analyzed meteorites.
The NWA 801 meteorite was found in Morocco in 2001, and has a mass of 5 kilograms. The Murchison meteorite fell in Australia in 1969, and has a mass of slightly more than 100 kilograms. Both meteorites are large enough and have been on Earth long enough to have become contaminated by ribose from Earth’s organisms.
Living organisms preferentially select carbon-12 over carbon-13. Therefore, the team of eight astronomers who discovered ribose in the NWA 801 and Murchison meteorites measured the carbon-12 to carbon-13 ratio in their discovered ribose. They determined that the ratio of carbon-13 to carbon-12 was high enough to rule out the ribose coming from Earth’s organisms or the remains of Earth’s organisms. Thus, they concluded that the ribose they found was extraterrestrial in origin. (It is highly unlikely, though not impossible, that the ribose was manufactured during entry into Earth’s atmosphere or upon impact.)
Implications of the Discovery for the Origin of Life
The origin-of-life research community greeted the discovery of ribose in the two meteorites with great enthusiasm. The lead author of the discovery team, Yoshihiro Furukawa, said that, “The extraterrestrial sugar might have contributed to the formation of RNA on the prebiotic Earth which possibly led to the origin of life.”4
The discovery of ribose and the failure to discover deoxyribose was viewed as evidence for the RNA world hypothesis for life’s origin. In this model, natural processes first produce RNA molecules which then naturally evolve into DNA molecules and proteins. (Ribose molecules are the links that join nucleobases together to make RNA molecules, whereas deoxyribose molecules are the links that join nucleobases together to make DNA molecules.)
However, there are scientific reasons for curbing the enthusiasm. The RNA world hypothesis needs a lot more than just the presence of ribose and nucleobases. There also needs to be a natural mechanism to link the ribose molecules and nucleobases together in the just-right sequences to make RNA molecules and protect the manufacturing processes from contamination and from destructive reactions. Furthermore, ribose molecules are manifested in two configurations: a left-handed orientation and a right-handed orientation. RNA requires that 100 percent of the ribose molecules be right-handed. Even under highly controlled, highly technical laboratory conditions, biochemists have been unable to join together more than 50 nucleobases. Though RNA molecules are not as long as DNA molecules, many life-critical RNA molecules consist of many hundreds of nucleobases. Leslie Orgel, the founder of the RNA world hypothesis, publicly declared at an origin-of-life conference that Fazale Rana and I attended, “It would be a miracle if a strand of RNA ever appeared on the early Earth.”5
Origin of Life Still Points to Creation
Personally, I have stated on public record for more than a decade that natural sources of ribose and deoxyribose will be found but only at abundance levels of a few parts per billion or less. I also have been on public record saying that such very low abundance levels will be of no help to any conceivable naturalistic origin-of-life model. The concentration levels need to be much higher, the ribose and deoxyribose molecules all need to be right-handed, all the different species of bioactive amino acids and nucleobases need to be present at high abundance levels, and all the bioactive amino acids must be left-handed in their configuration.
Such requirements, and there are many more, explain why five of the world’s most prominent origin-of-life researchers in their individual lectures at the XVIII International Conference on the Origin of Life in 2017, at the University of California, San Diego, all agreed that not only do we lack understanding of where the building blocks of life arise, we do not even understand where the “building blocks of the building blocks” of life arise.
There is now overwhelming evidence that scientists will never understand, from a naturalistic perspective, where the building blocks of the building blocks of life arise. However, from a supernatural, super-intelligent perspective there is no problem. The Bible states that life can only arise from life. As my colleague, Fazale Rana has explained and documented in his book, Creating Life in the Lab, it takes an eternal living Being with far more intelligence, knowledge, and power than we humans possess to create Earth’s first life.6
Check out more from Reasons to Believe @Reasons.org