Life on Mars?
Did it Come from Earth?
Life on Mars?
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Review of the "evidence" of past life on Mars from the meteorite AHL84001 shows that only those already persuaded could be convinced. The organic compounds found lack the oxygen, nitrogen and sulfur that compose the amino acids that form protein. The authors of the report in Science readily admit that "organic compounds" does not mean "biogenic compounds." The "evidence" from AHL84001, like Rorschach inkblots, tells us more about the role of preconceptions than about Mars.
President Clinton gave a news conference on the South Lawn of the White House on August 7, 1996. He spoke about the meteorite Allan Hills 84001 or for short, ALH84001 (See Figure 1). The President noted that ALH84001 had been picked up on a glacier in Antarctica in 1984. He discussed briefly the history of ALH84001 from its formation four billion years ago on Mars, its escape as a consequence of the shock from the impact of a body striking Mars, the 16 million-year journey through space and its arrival 13, 000 years ago on a glacier in Antarctica. He expressed both enthusiasm and caution on the question that ALH84001 carries "evidence" of past life on Mars. He supported an aggressive plan for the robotic exploration of Mars and noted that an unmanned mission to Mars is scheduled to lift off from Kennedy Space Center in November, 1996 and a second mission will lift off in December, 1996. He noted that the first mission is to land on Mars on July 4, 1997--Independence Day!
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| Figure 1. ALH84001, the meteorite causing the controversy. Much debate exists over what its composition actually means and over where the rock may have originated. Associated Press photo from NASA. |
Those scientists and their supporters who steadfastly desire manned missions to Mars were alarmed by the President's emphasis on robot exploration by unmanned missions. Robot explorations will be made before the "evidence" attained will persuade Congress to fund the enormously expensive manned missions to Mars. That will push the scheduling of manned missions, if they are ever made, to the middle of the twenty-first century and beyond the lifetime of living manned-mission enthusiasts.
Mr. Daniel Goldin, NASA Administrator, held a briefing on the "Discovery of Possible Early Martian Life" at the NASA Headquarters in Washington, DC. Mr. Goldin is well-known for his enthusiasm for the search for extraterrestrial intelligence, life on planets around stars, manned missions to Mars and the search for "evidence" of life on Mars. The several members of the team of scientists, McKay et al.1 reviewed the "evidence" provided by the scientific examination of ALH84001:
Each member of the team cautioned that the observations were neither conclusive nor confirming evidence for a biological origin. They pointed out a number of times that the term "organic compounds" does not necessarily mean "biogenic compounds". This provides a window of deniability that NASA ever said that ALH84001 had evidence of life on Mars. At the same time that is just what the President, the Congress, the press, and the public now believe.
In judging the "evidence" that ALH84001 may provide, let us remember that the President, the Vice President, and most of the members of the Senate and House are lawyers. Their concept of "evidence" differs from that in science. For example, a witness testifies that he saw me sitting on a bench across the street from a bank on three consecutive days at the same time. The bank was robbed the next day. That testimony is "evidence" or "probable cause" that I was casing the joint. Although I was just reading the morning paper, I would be put on the witness stand under oath and required to justify my suspicious actions. This, I argue, is a misleading use of "evidence," and distracts Congress and the public from the real scientific issues.
Mars is often portrayed to the public as our "brother" and most Earth-like planet, now that surface temperature and other factors have eliminated Venus in the search for life in the solar system. The question of life on Mars has a long and dismal history.2 Giovanni Schiaparelli (1835-1910) thought he saw "canali", or "channels", often mistranslated from the Italian as "canals." Percival Lowell (1855-1916), nearly a century ago, believed he could see markings on Mars he called "canals", that had been made by intelligent beings. He prepared a detailed map showing how the courageous Martians, superior to humankind on Earth, were building public works to aid in their survival on an aging and desiccating planet. This view of Mars has since proved to be poetical fantasy. Nevertheless, Mars has long been the darling of space enthusiasts.
The Martian sidereal day is 24.6229 hours, slightly longer than the Earth's sidereal day of 23.9345 hours. The inclination of the equator of Mars to the orbit is 23.98x; that of the Earth is 23.45x. But there the resemblance vanishes. Mars may be Earth's "little brother" because it is only 10.74 % as massive as the Earth. Its gravity is only 38% that of Earth--a 300-pound football player on Earth would weigh 114 pounds on Mars.
The sparse atmosphere of Mars, a near-vacuum pressure only 0.6% of that on Earth, is composed of 95.3% carbon dioxide, 2.7% nitrogen, 0.13% oxygen and traces of water and the noble gases. The mere trace of oxygen does not provide an ozone shield to protect the surface from the intense ultraviolet radiation from the Sun. Mars does not have an appreciable magnetic field to protect the surface from the ionizing radiation of solar flares. Because of its thin atmosphere, Mars has been subjected to sterilizing ultraviolet rays, the solar wind, and ionizing radiation since it lost its primeval atmosphere 4.5 billion years ago.
In spite of the well-known inauspicious nature of the climate of Mars for the survival of life, and even more so for the origin of life, five robot spacecraft were sent to the red planet to search for life in the early 1960s, at great expense to United States taxpayers.2 The flybys of Mariners 4, 6 and 7 returned television pictures that showed ancient impact craters much like those on the Moon. The features Percival Lowell had imagined disappeared like a wraith. Mariner 9 went into orbit in 1971 and operated for 11 months, returning pictures that showed four gigantic extinct volcanoes and a multitude of channels, some hundreds of kilometers long. (These channels are invisible from Earth and have nothing to do with the canals of Percival Lowell.) However, the number of meteoritic impact craters that overlay these channels showed that they must have been made very early in the history of Mars. Evidence for even very short-lived oceans on Mars can be seen only by the dedicated advocates of future Mars exploration.
In the summer of 1976, two Viking spacecraft arrived at Mars and were placed in orbit. Lander 1 touched down on July 20, 1976, andLander 2 on September 3, on the opposite side of Mars. The two orbiters and Lander 2 operated for two years while Lander 1 operated for six years. The instrument used to measure and identify organic matter, called a gas chromatograph-mass spectrometer, is sensitive to parts per billion. The only carbon compounds found on Mars were traced to the cleaning solvents used in the manufacture of the instrument.2 Thus two speculations fell with one blow: the existence of life on Mars, and one of the sources that had been proposed for organic matter in the ocean of primeval soup on Earth. Other tests for life on Mars also failed to detect any evidence of life, past or present. Nevertheless, further exploration of Mars is one of NASA's top priorities.
NASA must adhere to its official policy on the origin of life as it applies to Mars. The standard model for the origin of life is given by Christopher P. McKay3 in his NASA Urey Prize Lecture: Planetary Evolution and the Origin of Life:
The standard model of the origin of life on Earth was first given form by Oparin4 and Haldane and begins with the abiotic production of organic molecules. Abiotic chemical evolution is then thought to occur in the presence of liquid water, resulting in more complex structures leading to life itself and the onset of biological evolution. The standard model for the origin of life posits that life is a naturally emergent property of matter in Earth-like environments and would develop rapidly on any similar body.
This conjecture, coupled with theories for planet formation, results in the prediction that life should have originated on Mars in its early warm and wet period, from 4.0 to 3.0 billion years ago. The proposal that Mars, early in its history, had some complement of water and an atmosphere of carbon dioxide and nitrogen much more dense than today is not unreasonable.5,6,7,8 This is shown by channels that are very similar to canyons cut on Earth in catastrophic floods. But the mere presence of water flowing in channels is not sufficient; an ocean is required to develop a "primeval soup" that, according to standard theory, is necessary for the origin of life. The prospects for large oceans on Mars are much less than on Earth.
As the primeval magma cooled, the Earth's steam atmosphere condensed to provide enough water to cover the surface to 2,700 meters, or about 8,900 feet, deep. Estimates of the amount of water on the much smaller surface area of Mars vary from 10 or 20 meters to 200 meters. Proposals by both reduction mechanists and dialectical materialists for the required time to generate a "primeval soup" of prebiotic carbon compounds on a "suitable" planet vary from 100 million years to a billion. Proponents of the "life on Mars" scenario must establish that there were substantial oceans with a "primeval soup" on Mars for comparable lengths of time. I have showed in previous publications9,10,11 that there never was a "primeval soup" in the Earth's ocean, and by the same token, there never was a "primeval soup" on Mars.
McKay et al.1 call for Martian and earthly biomarkers suitable for identifying biogenic activity on Mars. Among such markers is the conspicuous fractionation of the light isotope 12C in the conversion of carbon dioxide to living matter by biochemical pathways. 13C is retained in the aqueous medium in which the inorganic reactions occur, primarily in dissolved bicarbonate.12,13 Consequently, on Earth or on Mars, substances generated by organisms capable of metabolism exhibit a decrease of carbon 13 between -20 and -40 x with respect to the atmosphere. This is consistent with the formation of kerogen, a fossilized biogenic substance related to petroleum, in the 3.8 billion-year-old sedimentary rocks found at Isua in Greenland. Schidlowski12 shows that inorganic carbonate, formed by well-known principles of physical chemistry, and the organic carbon of kerogen, are divided clearly into two groups by their isotopic composition.
According to the NASA standard model, one may take the isotopic character as a Martian biomarker by which one can judge the validity of the claim of McKay et al.1 of having found evidence of fossil life on Mars in the ALH84001 meteorite. Romanek,14 one of the authors of McKay et al.,1 reported that the 13C of the Martian atmosphere is x + 41.3 x and compatible with the atmosphere of Mars being the source of carbon in the carbonate of ALH84001. McKay et al.1 do not report kerogens or their graphitic derivatives in ALH84001. This is a telling blow to the belief that the carbonate in ALH84001 was generated by living organisms. ALH84001 is an igneous orthopyroxenite, not a sedimentary rock. Accordingly, this is a second telling blow to the belief that the carbonates in ALH84001 reflect biogenic activity.
Amino acids, the components of protein, are found in a number of meteorites, but not in ALH84001. The aromatic hydrocarbons found in ALH84001 do not show a propensity for the selection of 12C. They are composed solely of carbon and hydrogen. A proteinous sample of amino acids shows considerable oxygen and nitrogen as well as sulfur. These polycyclic aromatic hydrocarbons are not a biomarker for ALH84001.
McKay et al.1 rely on the morphology of the carbonate globules in their interpretation of biogenic origin, rather than on their isotopic composition. Speculations on the morphology of models of living organisms have a long and dismal history. Oparin4 referred to much of the literature on the origin of life in the nineteenth and early twentieth centuries, which proposed that life emerged from a primeval soup in the early ocean from "coacervates" or colloids. That was first proposed by Haeckel15 in 1866, and was widely discussed by scientists, theologians, and the public in the nineteenth century. The discussion of these efforts was so widespread among the theater-going public in 1878 (sixteen years before Oparin was born) that Sir William Schwenck Gilbert (1836-1911) ridiculed it by having Pooh-Bah, a comic, greedy, and conceited character, introduce himself by declaring that he could trace his ancestry back to a "pre-Adamic protoplasmal atomic globule".16
Jacques Loeb17, a convinced mechanist, cautioned in 1906 against the value of building models of living organisms that, like the round granules in colloidal material, merely resemble them but are not capable of development, growth, or reproduction.
We often see what we want to see. Coacervate droplets, colloidal precipitates or "proteinoids" proposed in attempts to imitate or to model the first cells and the origin of life are like Rorschach inkblots. They tell us more about the philosophical preconceptions of the investigators and space exploration enthusiasts than about the origin of life.
Mr. Goldin stated, at the NASA briefing, that if it is confirmed that ALH84001 and, perhaps, other meteorites actually do contain microfossils as "evidence for primitive life on Mars" that means that life originated independently on a planet other than Earth. It would follow then that life is common in the Milky Galaxy. But is it possible that there was a two-way flow of meteorites18 between Earth and Mars? The kerogen in the sedimentary rocks at Isua in Greenland tell us that life was swarming in the oceans of the Earth, 3.8 billion years ago. After the last sterilizing event of the Late Heavy Bombardment, and before 3.8 billion years ago, bodies as large as 100 kilometers in diameter continued to hit the rapidly spinning Earth. Could ejecta from the sedimentary rocks have escaped Earth, orbited about in space and struck Mars entering the primeval oceans of the time, carrying life with them? Only one successful inoculation from Earth is necessary for life to flourish in the oceans on early Mars.
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| Figure 2. This is a high-resolution scanning electron microscope image of an unusual tube-like structural form, less than 1/100th the width of a human hair, found in the meteorite ALH84001. This structure will be the subject of future investigations that could substantiate whether or not it is fossil evidence of primitive life on Mars 3.6 billion years ago. Associated Press photo from NASA. |
These Earth-born meteorites will not be destroyed on Mars as those from Mars are on Earth. There is no plate subduction on Mars and for about three billion years, no ocean. Virtually the entire inventory can be found on the surface of Mars, a much larger area and for a very much longer window of time than is available for the preservation of meteorites on Earth. There may be a treasure trove of Earth-based meteorites lying about on Mars for the picking.
When at last Mars is explored by humans, some of the meteorites they find may have come from the impact that caused the extinction of the dinosaurs, 65 million years ago. The colliding object must have been about 10 kilometers in diameter--that would be a rock bigger than Mount Everest, which is only 8.8 kilometers high. The object collided at a speed of 11 kilometers per second and developed an energy of 100 million megatons of TNT. This energy is sufficient to excavate a transient crater 45 to 60 kilometers deep. After the walls slumped, the crater would still have been 17 to 20 kilometers deep. The prime candidate for the site of collision is the buried Chicxulub crater in the Yucatan peninsula in Mexico.19 The Chicxulub multi-ring basin is about 180 kilometers in diameter, the result of one of the largest collisions since the Late Heavy Bombardment during the formation of Earth and Mars. The astronauts exploring Mars will have no doubt about what to look for. Borings at the Chicxulub crater have shown that in addition to the dolomite limestones, the crater is underlain by anhydrite (CaSO4). The evidence for exchange of meteorites between Earth and Mars is much stronger than the evidence for "primitive life on Mars" presented by McKay et al.1
McKay et al.1 conclude: "None of these observations is in itself conclusive for the existence of past life. Although there are alternative explanations for each of these phenomena taken individually, when they are considered collectively, particularly in view of their spatial association, we conclude that they are evidence for primitive life on early Mars."
The "evidence" that McKay et al.1 present is no better than "probable cause" in the legal sense, which justifies no conclusion but only further investigation. It is clear that the contrary conclusion equally fits the data. In science we are forced by the data to one or several credible conclusions, eliminating others. The measurements of the carbon isotopes do not show the required selection of 12C; ALH84001 is an igneous orthopyroxenite, not a sedimentary rock. The Martian carbonate globules are neither Pooh-Bah's "pre-Adamic protoplasmal atomic globules," Rorschach inkblots, nor evidence of primitive life on early Mars. To assert that ALH84001 exhibits evidence for life is to ignore genetics17 and accept Oparinism3.
The facts on the question of life on Mars are that we must leave the poetic fantasy of science fiction and reconcile ourselves that life on Earth has no complement on Mars. The question of funding manned missions to Mars reminds me of the great pyramids of ancient Egypt. Those magnificent engineering achievements served no practical purpose for the people of Egypt or the Pharaoh. They were all looted in antiquity. The Romans were more practical. They built aqueducts, bridges and roads.
Copyright © 1997 Hubert P. Yockey. All
rights reserved. International copyright secured.
File Date: 5.1.97