Thursday, April 21, 2016

The Murchison Meteorite and the Origin of Life

How did the first living being arise on Earth? A number of answers have been proposed to this question – yet no theory has been accepted as fact. Current scientific research suggests that the answer lies on our very own planet – albeit contained on an asteroid that originated far from Earth. The Murchison Meteorite, an object of great significance in the field of astrobiology, landed on Earth on September 28, 1969 near the quiet Australian town of Murchison at approximately 10:45 AM.1 Fragments from what later became known as the meteor scattered across the countryside – each containing evidence that would become crucial to astro-biological research.

A large fragment of the Meteorite.2
Closer examination of the meteorite fragments revealed an abundance of both right-handed and left-handed amino acids and evidence of nucleobases that are comprise both DNA and RNA.3 Nucleobases are defined to be “structures that play fundamental roles in in carrying genetic information of all living things.”4 To illustrate the importance of such a discovery, take DNA and RNA to be a computer. Nucleobases are then metaphorically thought of as the various components of the computer, such as the hard drive. While a hard drive is essential for the operation of the computer; a hard drive itself does not constitute a computer. Similarly, a nucleobase does not constitute DNA or RNA by itself, but it essential to their function. One must note that “samples were gathered soon after impact”,4 therefore it is reasonable to assume that the samples were not contaminated – meaning that all compounds on the meteorite were of extraterrestrial origin.

The discovery of right-handed amino acids and nucleobases on the Murchison meteorite may provide the missing link in determining the ultimate origin of life.5 While the Miller-Urey Experiment concluded that organic molecules, namely amino acids, can arise naturally on Earth, they were unable to create life from such compounds. The compounds created are necessary for life to develop, alone they are not sufficient for life to develop. Some combination of the extraterrestrial materials found on the Murchison Meteorite may provide the missing component necessary for life to arise.

For some scientists, the discovery of nucleobases led them to speculate that life on Earth arose from an extraterrestrial source.6 Scientists who subscribe to a theory about the origin of life known as Panspermia, a theory stating that life on Earth did not originate on it, continue to debate exactly how life was transferred to Earth.7 Most scientists advocating for the Panspermia theory agree that meteors like the Murchison Meteorite act as the vehicles for such a transmission.8 After an impact had occurred, the materials from a meteor would react with the materials present on Earth to create life. While this model seemingly makes sense, a fatal flaw is present. The model – as it is currently stated – assumes that the materials that may be present on an asteroid can survive an impact. Assuming that organic compounds and organisms capable of surviving such an impact exists – such materials could exist in most places in the Universe.9 The idea of hardy organisms capable of surviving implying widespread life throughout the Universe characterizes the so-called “Panspermia Paradox,” as dubbed by sources such as RealClearScience10 and Scientific American.11 Organic compounds and organisms honed by natural selection to survive in space for extended periods of time should be common throughout the Universe, spread by asteroids and comets – but such organisms have yet to be observed.

The findings on the Murchison Meteorite serve to clarify the paradox known as the “Panspermia Paradox.” The presence of nucleobases and both left and right handed amino acids confirms the longevity of certain organic compounds.12 The findings of the Murchison Meteorite necessitate a re-examination of current efforts to search for extraterrestrial life. Other asteroids must be collected and planets must be explored. If such molecules could survive on an asteroid – they are most likely present on other planets.


- Frank Kovacs