Chosen Planet

An Essay Originally Published in Salvo Magazine Volume 51

Updated periodically as new science emerges

For this is what the Lord says—

he who created the heavens,

 he is God; he who fashioned and made the earth,

 he founded it; he did not create it to be empty,

 but formed it to be inhabited— he says:

“I am the Lord, and there is no other.

                                                                                                             Isaiah 45: 18

Just a few short decades ago, the Earth was considered to be an ordinary planet, orbiting an ordinary star, lost in a vast galaxy of other stars, amid myriad other galaxies populating the Cosmos. Mindless processes produced the first living organisms, we were told, which slowly evolved over the eons to produce creatures like us¹. This secular myth was accepted hook line and sinker by the uneducated masses after its promotion by God-denying ‘high priests’, including the late Arthur C. Clarke, Carl Sagan and Richard Dawkins, and mindlessly parroted by a generation of science journalists unwilling to dig any deeper. Yet, with the exponential rise of human knowledge, this worldview is being radically over-turned by an avalanche of new science, that paints an entirely different picture of our world: one in which its exceptional properties for supporting a long-lived biosphere for the express benefit of humanity in particular, is coming to the fore; where life itself ‘terraformed’ the Earth under Divine instruction.

An Anomalous Solar System

Many lines of evidence show that the Earth is old; 4.543 billion years with an uncertainty of just one per cent. But the circumstances under which our planetary system was shaped were very unusual. Formed from the gravitational collapse of a vast cloud of gas and dust, the proto-solar system condensed into a relatively thin disk with the neonatal Sun at its center. The inventory of elements endowed to the solar system might have turned out to be much like any other were it not for the presence of at least two relatively close-by supernova events² which helped eject it from a nursery of other stars, but which also enriched the primordial solar system with relatively large quantities of heat-generating radioactive elements such as aluminum 26, thorium and uranium³. The aluminum 26, with its short half-life of 730,000 years, provided enough thermal energy to remove excess levels of volatiles including water, carbon monoxide and carbon dioxide which would have scuppered the future emergence of living creatures on our world. In contrast, the very dense and long-lived radioactive elements like uranium and thorium sank to the center of the primordial earth, where their prodigious heat has kept the planet in a geologically active state over billions of years.

The most recent research on star formation shows that the Sun is far from being an average star⁴. Indeed that distinction goes to stars with masses roughly 50 per cent less massive than the Sun, with luminosities only 5 per cent as bright and surface temperatures of 3600K⁴, comprising some 80 per cent of all the stars in the Universe. Many more are smaller L dwarfs that are unable to fuse hydrogen in their cores, or larger stars than the Sun that have much shorter lifespans. In the words of the  University of Rochester astrophysicist Adam Frank;

“Please stop calling our Sun an “average star. It is philosophically dubious and astronomically incorrect.^{4 ”}

The Moon-forming event, which is thought to have occurred about 100 million years after the neonatal Earth formed⁵, in a highly improbable, oblique collision with a Mars-sized object, helped remove still more volatiles from the primordial Earth, allowing it to eventually form relatively shallow oceans where the continental land-masses could eventually emerge from the sea floor.  The debris from this cataclysmic event formed a relatively large Moon in close proximity to the Earth, helping to stabilize its orbital inclination and over time, to slow down the rotation rate of our planet from just 5 hours shortly after the Moon’s formation, to its present leisurely rotation period of 24 hours.

For the first few hundred million years after its formation, the Earth would have looked black and golden from the vantage of outer space, from the vast amounts of solidified magna cooling on its surface as well as the prodigious levels of volcanic activity spewing out hot lava from the planet’s interior. Frequent collision events with smaller space debris like asteroids would also have exacerbated these hellish conditions, but eventually the prodigious levels of water vapor outgassed from its interior would have transformed our lava dominated planet into a blue water world still devoid of continental landmasses.⁵ But just as soon as the Earth cooled down enough to enable liquid water to flow on its surface, life appeared.

Life Terraforms the Planet

The standard evolutionary story is that life began as simple organisms and gradually progressed to more complex forms with the slow march of time, but the best scientific evidence now suggests that this life was already complex and biochemically sophisticated. This is based on isotopic evidence^6,7 from the analysis of ratios of carbon and sulfur isotopes in sedimentary rocks laid down over 3.5 billion years ago. Since these biochemical processes have an absolute requirement for highly complex protein enzymes to have been present, it completely eludes an evolutionary explanation. Then why did our Creator choose to begin Earth’s life story with microbes? The answer has less to do with evolution than it has with chemical sophistication. The simple answer is that microbes are, by some considerable margin, the hardiest creatures ever to have lived on our planet.

Microbes are the die-hards of the living world, being capable of surviving in very hot and cold temperatures, high and low pH environments, and can even thrive in a cocktail of toxic chemicals and radioactive environments. Once the planet cooled enough to allow the first microbes to survive, they were set to work removing a plethora of poisonous substances from the primordial Earth. In these early times, the Earth’s surface would have had large amounts of so-called vital poisons, substances that are required in small amounts for more complex life to thrive, but in higher concentrations, can prove lethal; substances like iron, copper, zinc, molybdenum, arsenic, boron, selenium and iodine, to name but a few. In their soluble forms such vital poisons would have stunted any new life forms coming on the scene but in chemically transforming these elements⁸ into insoluble ores and minerals, microbes not only  removed such vital poisons from the Earth’s water environments but also formed large deposits of the valuable minerals that are now mined for their use in high technology devices. This also makes sense from a creation point of view, as more complex organisms are far more sensitive to these toxins than microbes are. One other benefit that life brought to the Earth is that it greatly enriched the planet’s mineral and gemstone tally. According to Dr. Robert Hazen, a world-leading mineralogist, Earth has the greatest diversity of mineral species of any body in the Solar System.⁵ Over 4,600 mineral species have been identified on Earth. In contrast, Mars probably has about 500 and Venus about 1,000 at the most. What’s more, Hazen discovered that life processes formed about two-thirds of Earth’s mineral species⁵.

Recent oxygen isotope evidence shows that ongoing plate tectonic activity produced nearly all the continental landmasses by about 2.5 billion years ago.⁹ The fact that just 29 per cent of the planet’s surface area is covered by dry land appears to be highly fine-tuned. Greater land surface areas would induce too little precipitation in the interior of those ancient continents, preventing life from gaining a hold in these places. On the other hand, land areas significantly less than 29 per cent would not be able to re-cycle enough valuable nutrients between the land, the sea and the atmosphere to maintain a healthy biosphere.

The earliest lifeforms extracted energy from these minerals without the need for molecular oxygen, but the introduction of photosynthetic microbes radically transformed the early biosphere, paving the way for the introduction of advanced lifeforms. One way to get a handle on how early oxygenic photosynthesis occurred on Earth is to study so-called Banded Iron Formations (BIFs)comprised of iron rich clays containing magnetite and hematite. The early oceans had high concentrations of soluble iron, but when it reacts with oxygen, it forms an insoluble rust-like substance that serves as iron ore today.

Such studies reveal that BIFs were first laid down about 3.0 billion years ago, continuing up to about 1.8 billion years ago.¹⁰ This coincides with the microfossil record of life, which shows that oxygen-dependent complex cellular life (the so-called Eukaryotes) made its first appearance around 2 billion years ago.¹¹The rise in atmospheric oxygen also created the ozone layer, which protected future life on land from the damaging effects of ultraviolet radiation from the Sun. The emergence of oxygen-generating photosynthesis had other effects that are not immediately obvious. When the Sun was born, it was about 30 per cent less luminous than it is today, but as it aged, its luminosity increased with the result that the amount of thermal energy received by the planet also increased. Photosynthetic organisms removed great amounts of greenhouse gases from the atmosphere by absorbing carbon dioxide and generating oxygen which reacted rapidly with another greenhouse gas, methane. In so doing, photosynthetic organisms served to counteract the tendency of the aging Sun to overheat the planet.¹² The remains of these and other unicellular creatures settled to the bottom of the oceans where they formed vast sediments that were compressed over time to produce natural gas and oil reserves so important to human civilization today.

After a long cooling phase coinciding with the formation of the supercontinent, Rhodinia⁵, signs of the first large(macroscopic) multicellular lifeforms appeared about 600 million years ago in an event known to palaeontologists as the Avalon Explosion, where scientists have uncovered the first evidence of simple animal lifeforms. It is unclear however whether these bizarre creatures were animals or plants but what is clear is that in the space of a short 410,000 year period starting around 541 million years ago, 80 per cent of all existing animal forms appeared in the fossil record, with no credible evolutionary antecedents^3,22. Paleontologists studying the so-called Cambrian Explosion have found no transitional forms in layers immediately pre-dating this period in Earth history. Moreover, the land was being prepared for the arrival of vascular plants by fungi who began breaking down rocks into soil as early as about 1000 million years ago¹⁴.  It is difficult to conceive how any blind process like Darwinian evolution could produce such stunning biological complexity and diversity in such a short space of time without any foresight.

In recent times, a greater appreciation of the interplay between life and plate tectonics has been appreciated. Without plate tectonics, our planet wouldn’t have a climate stable enough to support life over billions of years of time. That’s because plate tectonics takes center stage as a planetary thermostat in a process called the “carbonate-silicate” cycle.¹³ Carbon dioxide in the atmosphere dissolves in rainwater to form carbonic acid, which dissolves silicate rocks. The by-products of this erosion, or “weathering,” are conveyed to the oceans where they are ingested by organisms—such as tiny planktonic foraminifera—and incorporated into limestone (calcium carbonate) shells. When those creatures die, they fall to the bottom of the ocean and pile up as sediments, creating new raw materials used by humanity. The introduction of life on planet Earth also increases the amount of water subducted into the mantle, where it functions as a kind of lubricant, facilitating motions between plates. It also lowers the melting point in the mantle, which leads to more volcanism and therefore more continent building. So, without life speeding up the weathering at the surface as well as the sedimentation rate on the sea floor, the fraction of the surface covered by continents would be far smaller.

Plate tectonics has other, hitherto unforeseen consequences for the maintenance of the Earth’s strong magnetic field.  By accelerating the transfer of heat to the surface, plate tectonics induces convection in the liquid iron outer core of our planet. What’s more, it’s the dynamic outer core that generates our planet’s magnetic field, which protects Earth’s atmosphere and oceans from excessive erosion and desiccation from the solar wind as well as all surface life from dangerous cosmic rays.

The fossil record attests to several mass extinction events that occurred over the long history of our planet.¹⁴ Research has shown that these devastating events are followed by equally spectacular mass speciation events, uncannily similar to the scenarios described in Psalm 104. According to Christian astronomer, Dr. Hugh Ross, these events proved crucial for maximizing both the quantity and longevity of Earth’s life.¹⁵ By ensuring that the right quantities and kinds of life are present at the right times, our Creator employed these organisms to remove the just-right quantities of greenhouse gases from Earth’s atmosphere so as to compensate for the Sun’s increasing brightness. According to Ross, one would expect God to intervene periodically to remove life no longer appropriate for compensating for a brightening Sun and then replace it with life that is more efficient at doing so. Finally, in the last few hundred million years, vast deposits of coal and oil were produced from the remains of plant life that flourished on land during the Carboniferous and Permian (360 to 250 million years ago) periods, which was necessary for the launch of the industrial revolution.

Jewel Planet

Seen in the light of these new scientific discoveries, it is apparent that the Earth is a highly fine-tuned planet that has sustained a very stable environment over 4 billion years for the flourishing of life. And that same life transformed our world beyond recognition to make it ideal for humans to thrive in. This consensus is now being expressed by other scientists, who have noted Earth’s amazing properties. Influential books like Donald Brownlee and Peter Ward’s Rare Earth¹⁸: why complex life is are in the Universe, David Waltham’s Lucky Planet¹⁹, John Gribbin’s Alone in the Universe²⁰ as well as Privileged Planet²¹by Guillermo Gonzalez and Jay Richards, all seem to be singing from the same hymn sheet. Far from being a humdrum planet orbiting an ordinary star, the Earth was designed by a mind vastly more advanced than our own. And I give God all the glory!

Neil English is the author of several books in amateur astronomy. His latest historical work, Chronicling the Golden Age of Astronomy, is published by Springer-Nature.

References

1. Sagan, C. Cosmos, MacDonald Futura Publishers, London, 1981.
2. Eric Gaidos et al., “26Al and the Formation of the Solar System from a Molecular Cloud Contaminated by Wolf-Rayet Winds,” Astrophysical Journal 696 (May 10, 2009): 1854–63.
3. Ross, H., Elemental Evidence of Earth’s Divine Design; https://reasons.org/explore/publications/nrtb-e-zine/read/nrtb-e-zine/2010/03/01/elemental-evidence-of-earth-s-divine-design
4. Frank, A., What is the “Avergae Star” like? Hint: It’s not like our Sun: https://bigthink.com/13-8/average-star/

5. Hazen, R. The Story of Earth, Penguin, 2012.
6. Allen P. Nutman et al., “≥3700 Ma Pre-Metamorphic Dolomite Formed by Microbial Mediation in the Isua Supracrustal Belt (W. Greenland): Simple Evidence for Early Life?” Precambrian Research 183, no. 4 (December 15, 2010): 725–37.
7. Yanan Shen et al, “Isotopic Evidence for Microbial Sulphate Reduction in the Early Archaean Era,” Nature 410 (March 1, 2001): 77–81.
8. Gadd, G.M., Metals, minerals and microbes: geomicrobiology and bioremediation https://mic.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.037143-0;jsessionid=CfnAVoIxE-Nxln81QM-D2S0N.x-sgm-live-02
9. N. Bindeman et al., “Rapid Emergence of Subaerial Landmasses and Onset of Modern Hydrologic Cycle 2.5 Billion Years Ago,” Nature 557 (May 23, 2018): 545–48, https://doi:10.1038/s41586-018-0131-1.
10. James, H.L. (1983). Distribution of banded iron-formation in space and time. Developments in Precambrian Geology, 6, 471–490.
11. Simonetta Gribaldo et al., “The Origin of Eukaryotes and Their Relationship with the Archaea: Are We at a Phylogenomic Impasse?” Nature Reviews Microbiology 8 (2010): 743–52.
12. Ross, H. Improbable Planet, Baker Books, 2016.
13. Ross, H., Cambrian Explosion Becomes More Explosive:                                   https://reasons.org/explore/blogs/todays-new-reason-to-believe/cambrian-explosion-becomes-more-explosive
14. https://theconversation.com/complex-life-may-only-exist-because-of-millions-of-years-of-groundwork-by-ancient-fungi-117526
15. Walker, J.C.G., Hays, P.B., & Kasting, J.F. A negative feedback mechanism for the long-term stabilization of Earth’s surface temperature. Journal of Geophysical Research 86, 9776-9782 (1981).
16. Melott & Bambach, “Do Periodicities in Extinction—With Possible Astronomical Connections—Survive a Revision of the Geological Timescale?” Astrophysical Journal 773 (August 10, 2013).
17. Ross, H. Mass Extinction Periodicity Design; https://www.reasons.org/explore/publications/nrtb-e-zine/read/nrtb-e-zine/2013/12/01/mass-extinction-periodicity-design
18. Brownlee, D. & Ward, P., Rare Earth, Why Complex Life is Uncommon in the Universe, Springer, 2000
19. Waltham, D., Lucky Planet, Icon Books, 2015
20. J., Alone in the Universe; Why our Planet is Unique, John Wiley, 2011.
21. Gonzalez, G. & Richards, J, The Privileged Planet: How Our Place in the Cosmos Is Designed for Discovery, Regnery Publishing, 2004.
22. Ross, H., Cambrian Explosion Becomes More Explosive: https://reasons.org/explore/blogs/todays-new-reason-to-believe/cambrian-explosion-becomes-more-explosive

De Fideli.

Originally Published in Salvo Magazine Volume 50

“Life should not exist. This much we know from chemistry. In contrast to the ubiquity of life on Earth, the lifelessness of other planets makes far better chemical sense.” So writes Professor James Tour, one of the world’s foremost synthetic organic chemists, based at Rice University in Texas. Intimately acquainted with the latest research in prebiotic chemistry, Tour has expressed severe skepticism that a plausible naturalistic mechanism for the origin of life will be found any time soon. But he goes even further:

“We synthetic chemists should state the obvious. The appearance of life on Earth is a mystery. We are nowhere near solving this problem. The proposals offered thus far to explain life’s origin make no scientific sense. Beyond our planet, all the others that have been probed are lifeless, a result in accord with our chemical expectations. The laws of physics and chemistry’s Periodic Table are universal, suggesting that life based upon amino acids, nucleotides, saccharides and lipids is an anomaly. Life should not exist anywhere in our Universe. Life should not even exist on the surface of the Earth.”¹

Dr. Tour’s views have surfaced at a time when astronomers have been peering into the depths of space, searching for intelligent signals from hypothetical alien civilizations. Yet although they have been listening for more than half a century, ET has not chimed in. The quest to detect life beyond the Earth is admittedly in its infancy, but the negative results thus far produced have caused more than a few scientists to question the underlying assumptions made by the early pioneers in the quest to find extra-terrestrial life: Frank Drake and Carl Sagan.

Despite what the general media report, there are a number of serious problems with the standard origin-of-life models, for which their proponents have failed to provide good answers. For example, life on Earth requires a source of homochiral molecules, that is, molecules that are capable of rotating the plane of polarized light either to the left (L) or to the right (D). Specifically, life invariably requires L amino acids and D sugars. But so far, chemists have been unable to identify a plausible natural mechanism by which these left- and right-handed biomolecules can be generated at the high level of purity necessary for the first cells to form. Indeed, such molecules can only be synthesised under highly constrained laboratory conditions, using purified (read bought in) reagents, which have little or no relevance to the environment of the early Earth. And while meteorites have been found that contain small amounts of amino acids, they invariably are shown to contain equal amounts of L and D isomers (technically known as a racemic mixture).

In short, no conceivable naturalistic scenario could result in the generation of the large, stable ensembles of homochiral ribose and homochiral amino acids that all naturalistic origin-of-life models require, affirming why no such natural sources have ever been found.² I recently asked Dr. Tour directly if the problem of homochirality had been solved, and he firmly responded, “No; it is far from solved.”

The Phosphorus Conundrum

The element phosphorus is vital for the proper functioning of living cells, being a constituent of both RNA and DNA, as well as of adenosine triphosphate (ATP), the universal energy currency of all known life forms. But recent work conducted by Cardiff University astronomers suggests that phosphorus could be scarce in many parts of the universe. “Phosphorus is one of just six major chemical elements on which Earth organisms depend,” says Dr. Jane Greaves, and it is crucial to the compound ATP, which cells use to store and transfer energy. Astronomers have just started to pay attention to the cosmic origins of phosphorus and found quite a few surprises. In particular, phosphorus is created in supernovae—the explosions of massive stars—but the amounts seen so far don’t match our computer models. I wondered what the implications were for life on other planets if unpredictable amounts of phosphorus are spat out into space and later used in the construction of new planets.³

The Cardiff team used the UK’s William Herschel telescope, situated on La Palma in the Canary Islands, to measure the levels of phosphorus and iron in the Crab Nebula, a well-known supernova remnant. They compared those figures to measurements taken earlier from another supernova remnant known as Cassiopeia A (Cas A). Their preliminary results proved very surprising. While the measurements of Cas A showed relatively high levels of phosphorus, those from the Crab Nebula showed far lower levels. “The two explosions seem to differ from each other, perhaps because Cas A results from the explosion of a rare type of super-massive star,” said Dr. Phil Cigan, another member of the Cardiff team. “If phosphorus is sourced from supernovae,” added Greaves, and then travels across space in meteoritic rocks, I’m wondering if a young planet could find itself lacking in reactive phosphorus because of where it was born? That is, it started off near the wrong kind of supernova? In that case, life might really struggle to get started out of phosphorus-poor chemistry on another world otherwise similar to our own.⁴

Re-evaluating the Drake Equation

Ever since the American astronomer Frank Drake introduced his famous eponymous equation in the early 1960s, astronomers have produced widely varying estimates of the number of extant extra-terrestrial civilizations present in the Milky Way Galaxy. Until fairly recently, the estimates varied from 10,000 to a few million. Countering these estimates, some scientists have re-examined the so-called Fermi Paradox, posed by the distinguished Italian physicist Enrico Fermi in the form of a question: If the universe is so large, with innumerable habitable planets, then why have we not detected any sign of ET?

A team of scientists and philosophers based at the Institute of Humanity in Oxford University has taken a new look at the reasoning behind the Drake equation, and found that its optimistic expectations are linked to models like the Drake equation itself. The problem, as these researchers point out, is that all such models “implicitly assume certainty regarding highly uncertain parameters.” Indeed, following an analysis, they concluded that “extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude.” When these uncertainties are introduced, the outcome is strikingly different: “When the models are re-cast to represent realistic distributions of uncertainty, we find a substantial ex ante probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it.” This result, they assert, “dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.”⁵

Questioning the Mediocrity Principle

Over the past few decades, astronomers have discovered thousands of exo-planets orbiting nearby stars, so that now there is little doubt that the number of planets in the observable universe likely exceeds the number of stars. Exo-planet hunters have discovered that many of these planets orbit their stars within the so-called habitable zone—that narrow annulus around a star that allows for the stable existence of water on a planet’s surface. Nevertheless, as geologist Peter Ward and astronomer Donald Brownlee argued in their highly influential book, Rare Earth; Why Complex Life Is Uncommon in the Universe,⁶ many of the features of planet Earth that have made it suitably equipped to allow both microbial and complex life to flourish on it over billions of years are likely very rare in the rest of the Universe.

For instance, the vast majority of potentially habitable exo-planets orbit low-mass red dwarf stars, which make up 75 percent of all the stars in the galaxy.⁷ These stars are much more active than sun-like stars, thus exhibiting higher rates of flaring than does the Sun. Many such stars also generate strong stellar winds that could strip away the atmospheres of their planets.⁸ And many planets are located so close to their parent stars that they have become tidally locked, meaning that they do not rotate on an axis but constantly present the same face to their stars as they move in their orbits. Yet another issue pertains to the potential of gravitational perturbations of a habitable planet by its neighbouring planets. Even small changes to the orbital characteristics of a planet could extirpate any developing life that might exist upon it. All these conditions raise many problems for the development of any hypothetical life forms on the surface of these planets over long periods of time.

NASA’s Hubble Space Telescope is currently being utilized in a special program called HAZMAT—Habitable Zones and M Dwarf Activity Across Time. And the early results from the program do not look encouraging. Preliminary data on just a dozen young red dwarf stars show that the frequency of flaring is much higher in them than in stars like the Sun; they typically emit flares with energies that are between 100 and 1,000 times higher than those of their elder counterparts. The most energetic red dwarf flares, dubbed Hazflares, are far more energetic than the most energetic flares ever to come from the Sun. “With the Sun, we have a hundred years of good observations,” says Parke Loyd, a member of the scientific team involved in the project.

And in that time, we’ve seen one, maybe two, flares that have an energy approaching that of the Hazflare. In a little less than a day’s worth of Hubble observations of these young stars, we caught the Hazflare, which means that we’re looking at superflares happening every day or even a few times a day.⁹

So-called super-earths—worlds larger than the Earth but smaller than Neptune—have recently been identified as possible candidate worlds for the development of life, but there is as yet no scientific consensus on whether they can maintain or even allow plate tectonic activity to occur in their crusts. Without plate tectonics, there will be far less efficient nutrient re-cycling, which would greatly hinder the flourishing of hypothetical life forms.

In March 2019, a team of astronomers based at the Australian National University dealt yet another blow to the prospects of finding viable exo-planetary biosystems. Modelling the magnetic fields of a large number of exo-planets, the astronomers concluded that planets with a strong magnetic field, like Earth, are likely to be very rare. “Magnetic fields appear to play an essential role in making planets habitable, so I wanted to find out how Earth’s magnetic field compared to those of other potentially habitable planets,” says Sarah Macintyre, the lead author of the paper.¹⁰ “We find most detected exo-planets have very weak magnetic fields, so this is an important factor when searching for potentially habitable planets,” she added.

Life on Mars or Venus?

Scarcely a year goes by without the question arising of whether or not Mars has microbial life. This issue was brought into sharp focus in June 2018, when NASA scientists announced the discovery by the rover Curiosity of organic matter in the soil of an ancient lakebed.¹¹ But “organic matter” means different things to different people. Simply put, matter that is carbon-rich is not necessarily derived from biogenic sources.

More broadly though, if evidence of either extant or past life on Mars is uncovered, it might well also be discovered that such life originated on Earth. Indeed, it is estimated that over the 4-billion-year history of life on Earth, so much terrestrial soil has found its way to Mars that the Red Planet can boast an average of 2 kilograms of terrestrial soil per square kilometre of its surface (or about 11.3 pounds per square mile).¹² It is certainly possible that some microbial life was delivered there along with the soil—in fact, the discovery of either extant microbial life or microfossils on Mars or the recent claim of life in the clouds of Venus might well be anticipated. If that happens, astrobiologists will need to consider the possibility that it came from Earth before claiming that any such life originated on these worlds. The popular media, pushing sensationalism, would never be so cautious.

Questioning Biosignatures on Exo-planets

Oxygenic photosynthesis by plants is the mechanism that produces the vast majority of the molecular oxygen in the terrestrial atmosphere. So for several decades, astrobiologists have speculated that the detection of oxygen in the atmosphere of an exo-planet would provide good evidence that life must exist there.¹³ While the detection of substantial levels of this gas would certainly be suggestive of the presence of plant life as we know it, it pays to remember that there are established abiotic mechanisms (mechanisms derived from non-living sources) that also can generate substantial molecular oxygen.

A group headed by Chinese astronomer Feng Tian of Tsinghua University published two interesting papers in 2009 that show that stars having less than 50 percent of the mass of the Sun (i.e., the majority of stars) emit copious quantities of hard UV rays and soft X rays throughout their long nuclear burning phases of up to 10 billion years.¹⁴ They also showed that when a lifeless exo-planet possessing carbon dioxide in its atmosphere is irradiated, the rays can break down the CO₂ into carbon atoms and molecular oxygen. Over time, the carbon atoms, being less massive, escape into space, leaving the molecular oxygen behind. Tian’s calculations show that this molecular oxygen can reach concentrations of a few percent and so might be confused with a genuine biosignature.

 When a team of chemists from Johns Hopkins University simulated the atmospheres of exo-planets beyond the solar system, they found that they could create simple organic molecules and oxygen under various scenarios without the mediation of life.¹⁵ “Our experiments produced oxygen and organic molecules that could serve as the building blocks of life in the lab, proving that the presence of both doesn’t definitively indicate life,” says Chao He, assistant research scientist in the Johns Hopkins Department of Earth and Planetary Sciences. “Researchers need to more carefully consider how these molecules are produced.” Up-and-coming missions, such as the highly anticipated ones utilizing the James Webb Space Telescope, would need to take results like these into account before jumping to any firm conclusions about the habitability of a candidate planet. As a case in point, the recent flap in the media about the detection of phosphine on Venus, upon further analysis, showed that the biomarker in question was not,  in fact, present in statistically significant levels.

In a recent development, a team of planetary scientists led by Li Zeng at Harvard University estimated that as many as 35 percent of exo-planets may have impenetrable water oceans hundreds of kilometres deep.¹⁶ But while NASA has long adopted the mantra, “follow the water,” the same scientists caution that these planets are very unlikely to be habitable. Their fathomless ocean worlds would generate pressures millions of times greater than those found on Earth, resulting in exotic, rock-like ice formations many kilometres deep (such as ice VII) covering their floors. Such conditions would prevent any nutrient recycling from occurring, thus rendering these planets sterile.

Call for Caution

Investigating whether extra-terrestrial life exists or not is a profoundly important and interesting scientific endeavor, but at this point, there are good grounds for remaining skeptical about whether it actually exists. Given the arguments raised in this article, it is entirely reasonable to think that life might be extraordinarily rare in the universe, perhaps even unique to Earth. Only time will tell.

Notes

1. James Tour, An Open Letter to My Colleagues (August 2017): http://inference-review.com/article/an-open-letter-to-my-colleagues.
2. Hugh Ross and Fazale Rana, Origins of Life (RTB Press, 2014).
3. “Paucity of phosphorus hints at precarious path for extraterrestrial life” (Apr. 4, 2018): eurekalert.org/pub_releases/2018-04/ras-pop040318.php.
4. Ibid.
5. Anders Sandberg et al., “Dissolving the Fermi Paradox” (June 8, 2018):

https://arxiv.org/pdf/1806.02404.pdf.

6. Peter D. Ward and Donald Brownlee, Rare Earth; Why Complex Life Is Uncommon in the Universe (Copernicus Books, 2000).
7. “Superflares from young red dwarf stars imperil planets,” NASA News (Oct. 22, 2018):

https://exoplanets.nasa.gov/news/1527/superflares-from-young-red-dwarf-stars-imperil-planets.

8. O. Cohen et al., “Magnetospheric Structure and Atmospheric Joule Heating of Habitable Planets Orbiting M-Dwarf Stars,” Astrophysical Journal 790 (July 2014): doi:10.1088/0004-637X/790/1/57.
9. Ibid., note 7.
10. “Strong planetary magnetic fields like Earth’s may protect oceans from stellar storms,” Royal Astronomical Society (Mar. 14, 2019): https://m.phys.org/news/2019-03-strong-planetary-magnetic-fields-earth.html.
11. Jennifer L. Eigenbrode et al., “Organic Matter Preserved in 3-Billion-Year-Old Mudstones at Gale Crater, Mars,” Science 360 (June 8, 2018): https://doi:10.1126/science.aas9185.
12. Ibid., note 2.
13. Carl Sagan et al., “A Search for Life on Earth from the Galileo Spacecraft,” Nature 365 (Oct. 21, 1993): nature.com/articles/365715a0.
14. Feng Tian, “Thermal Escape from Super Earth Atmospheres in the Habitable Zones of M Stars,” Astrophysical Journal 703 (Sept. 2, 2009): https://dspace.mit.edu/bitstream/handle/1721.1/96200/Tian-2009-THERMAL%20ESCAPE%20FROM.pdf;sequence=1; Feng Tian et al., “Thermal Escape of Carbon from the Early Martian Atmosphere,” Geophysical Research Letters 26 (Jan. 31, 2009): https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL036513.
15. Chao He et al., “Gas Phase Chemistry of Cool Exoplanet Atmospheres: Insight from Laboratory Simulations,” ACS Earth Space Chemistry (Nov. 26, 2018): https://pubs.acs.org/doi/10.1021/acsearthspacechem.8b00133.
16. Li Zeng et al., “Growth model interpretation of planet size distribution,” PNAS (Apr. 29, 12019): pnas.org/content/early/2019/04/23/1812905116.

Neil English has been following developments in pre-biotic chemistry and astrobiology for the last 25 years. He holds a Ph.D. in biochemistry and a BSc(Hons) in physics & astronomy. His latest book, Chronicling the Golden Age of Astronomy (Springer, 2018), explores four centuries of visual astronomy. The article first appeared in Salvo Magazine Summer 2019. You can support his ongoing work by making a small donation to his website. Thanks for reading!

De Fideli.