Meteors: Harbingers of Life
How life began on our planet is an enduring question fraught with theological and scientific tension. While ascribing the origin of life to a divine creator is satisfying and comforting to many, the need to understand the scientific process that led to the creation of life is compelling. Though we understand the broad outlines of the process, it is still a venture riddled with conjecture and uncertainty. There is no lack of attempts to comprehend it. See the following article for more information: Where did life originate?
In light of this question, let us look at the role that meteors plausibly play in the development of life on this planet. Though we all have a vivid image of how destructive meteor strikes can be, it would also be worthwhile to consider the upside of their presence.
First, we have to distinguish the different types of meteorites (meteors which survive transit through the Earth’s atmosphere). Broadly speaking, there are two types: stony and metallic. The most common type of meteorite is Stony, meaning it is silicate-rich. Within this group there are chondrites and achondrites. Generally, 85% of the meteorites that have been studied are chondrites. A chondrule refers to a molten drop thought to have been created when the Solar System was formed. Chondrules containing organic material are carbonaceous, though they usually contain other minerals as well. While the ordinary chondrites contain minerals such as olivine, feldspar, and silicates, they are absent of carbon molecules. The other 15% of all meteorites are either metallic, containing iron and nickel alloys, or stony-iron, containing varying proportions of silicates and iron. Over the years, a wealth of subclassification systems has arisen based on the composition of and proportions of material found in meteorites.
Obviously, the origins of life on Earth must have begun with the creation of the Earth itself, some 4.5 billion years ago. Any current self-respecting astronomy textbook will lay out the most probable course. This includes the gravitational compression of interstellar dust (called the Nebular Theory), leading to the creation of a spinning disk, and then accretion, which includes the formation of planets and collisions between planets, moons, asteroids, and other planetary bodies. For more information on the creation of our Solar System, see The Cosmic Perspective (Pearson 2024, 10th Edition, Chapter 7).
After the formation of an Earth-Moon system, the continuing barrage of meteor and asteroid strikes triggered an outflow of material from the Earth’s core. This, in and of itself, set the stage for the presence of the kinds of organic molecules that would catalyze our own biological evolution. See the following article for further information: Organics probably formed easily in early solar system | University of Chicago News.
They created a “soup” of methane, ammonia, hydrogen, and water vapor, then struck the mixture with electrical sparks to simulate the lightning strikes in Earth’s early atmosphere. They found that organic molecules like amino acids had been created from this process. Subsequent studies essentially support the plausibility that organic molecules can be formed from inorganic compounds.
Over the billions of years in which the Earth underwent continual changes, it was also being bombarded with meteor and asteroids. Comparable to the energy contained within lightning strikes, the tremendous energy associated with these collisions may also have induced the inorganic material contained within the meteorites to form organic molecules. Furthermore, 4% of these colliding meteorites are, in fact, carbonaceous. They already possess organic molecules, including amino acids. See the following article for an overview: Carbonaceous Meteorite – an overview | ScienceDirect Topics.
It should also be pointed out that, leaving aside the impact of large meteorites, the Earth has been continually bombarded, over billions of years, with thousands of tons (every year) of interstellar dust; some of which also contain amino acids (Brownlee and Matrajt, 2005).
As early as 1969, evidence of amino acids in meteorites was confirmed in the famous 100 kg meteorite that fell in Murchison, Victoria, Australia.
A 2010 analysis of this meteorite uncovered some 14,000 organic molecules with more than 70 amino acids (Schmitt-Koppler et al., 2010). The study, in the words of the authors, “suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biological- and biogeochemical-driven chemical space.”
More recent computer-driven spectroscopic studies that analyze carbonaceous meteorites more intensively find far more amino acids than the twenty amino acids needed for life on Earth (Elmasry et al., 2020).
Serious concerns with the studies hypothesize that all the analyses may in fact be sampling meteorites that have been contaminated with amino acids from Earth during their descent or while being handled. See the following article for more information: Meteoritic and asteroidal amino acid heterogeneity: Implications for planetesimal alteration conditions and sample return missions – ScienceDirect. Only repeated validation of these studies will assure us with scientific certainty that the source of the amino acids in these meteors is interstellar.
Nevertheless, the abundance of scientific research, so far, favors the notion that meteors carry amino acids, biologically necessary or not, from interstellar space. This provides our planet with the seeds of life. Such awareness compels us to pause and reflect on the life-affirming connection of our Earthly existence to these often disturbing visitors from the cosmos.
