By Alexander PORTNOV, Dr. Sc. (Geol. & Mineral.), Moscow University of Geological Prospecting

Articles in this rubric reflect the opinion of the author. - Ed.

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There must have been life on Mars after all. Life destroyed by asteroids (planetoids). The planet's surface was scorched, and its oxygen-rich atmosphere escaped into outer space as plasma fluxes of hot gas. It might be that meteorites composed of Martian rock reached our planet too-the rock found in the ice- bound Antarctic and in Australia. In one such sample American researchers detected trace amounts of bacteria and organic matter rich in the light isotope of carbon, which is characteristic of vital activity processes.

The blood-red disk of Mars rising in the night sky in years when the planet approaches closest the earth (opposition) has always been regarded as a bad omen. That is why the Babylonians identified it with Nergal, the god of war, diseases and death. To Hellenes it was the war god Ares, otherwise known as Mars in ancient Rome. Opposition of the two planets, Mars and earth, heralds the cruelest of wars. Like, for instance, the opposition, of 1940 - 1941 during the Second World War, just before Germany attacked the Soviet Union.

Mars is often called the Red Planet. But why is it red? Why is this crimson color of blood?.. Strange as it may seem, this likeness is due to one and the same cause, the presence of red iron oxide. It is likewise present in the hemoglobin of blood. The Martian surface is strewn with red ferrous sand. In spite of the highly rarefied atmosphere (in density it corresponds to our atmosphere at an altitude of 30 km), violent sandstorms rage on Mars making its surface features invisible to astronomers now and then.

According to data obtained by US probes, the Martian ground and its bedrock abound in deep-seated andesites and basalts with a high concentration of iron monoxide (FeO) in silicate minerals. All this is covered with magmatic rock wastes (detritus). The Martian soil is poor in potassium oxide (0.1 percent) and not so rich in silica (45 percent), but it has an enhanced concentration of oxides of magnesium (8 percent), calcium (5 percent), titanium (1 percent), and has much of the sulfates (to 10 percent) and iron oxides (to 20 percent).

The red Martian ground is composed of iron oxides and hydroxides with impregnations of ferruginous clay and calcium and magnesium impurities. Here on earth this set of minerals is typical of thick red crusts of weathering formed in a warm climate what with the abundance of water and free oxygen of the atmosphere. Such rocks must have also appeared on Mars under similar conditions. That planet is red because its dark deep-seated rocks are buried under a layer of "rust" several kilometers thick. We can only wonder at the acumen of medieval alchemists who chose the sign of Mars for a symbol of iron.

In fact, the "rust" on the surface of a celestial body is the rarest phenomenon in the solar system-found on Mars and on earth only. The other bodies-say, like Jupiter's satellites Ganymede and Callisto-though quite rich in water, have been keeping deep- seated dark rocks virtually intact for billions of years. More than that, acted upon by the solar wind, cosmic rays and impact of meteorites, many of the metals are reduced to the

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native state; this process is most conspicuous on the moon.

The red sands of Mars are actually the windblown detritus from a thick crust of abysmal rocks. The close-up photos of the giant Martian river valleys indicate the depth of these formations to be no less than 3 to 5 km! They are very much like the terrestrial red crusts of weathering formed in a hot and humid climate. Rain water decomposes silicate minerals, while the iron within them stays, and detritus builds up to hundreds of meters. In the past geological epochs, when a hothouse climate reigned on earth, a crust of reddish rocks coated the surface of its continents. And if we add the ferruginous quartzites of the early Pre-Cambrian (3.2 - 2 bin years ago), the total depth of such formations amounted to many kilometers. That's when free oxygen appeared in the atmosphere. The oxygen atmosphere of the earth gave birth to life. The overall amount of oxygen-as much as 1,200 thous. bin tons-is produced by green plants in a matter of 3,700 years, a very short time geologically. And if these plants perish, free oxygen will disappear pretty fast: it will combine with organic matter again and, within carbon dioxide, oxidize iron in geological rock.

Now, the Martian atmosphere. It contains a mere 0.1 percent of free oxygen and 95 percent of carbon dioxide; the rest is nitrogen and argon. Clearly, the present amount of free oxygen is too low to have turned Mars into the Red Planet of today. Which means that the "rust" appeared much earlier. A huge quantity of water and oxygen was needed for that. The far-flung network of rivers ("channels") shows the erstwhile abundance of water there. And now, after the joint Russian-American experiment, we know there is a lot of ice on Mars.* And the most intriguing question: How much of the free oxygen did escape from the atmosphere to oxidize the rock to its present ochre color?

The surface of Mars makes up 28 percent of the earth's. According to my estimates, its atmosphere lost as much as 5,000 thous. bin tons of free oxygen, or four times as much contained in the terrestrial atmosphere today, for the formation of a 1 km-thick crust of basalt weathering detritus. Yet another 500 thous. bin tons of oxygen went into the building of a ten-meter stratum of sulfates.

True, sodium, magnesium and iron sulfates are detected in large amounts on one of Jupiter's satellites, lo. Here they owe their origin to the fantastic phenomenon of "sulfur" volcanicity, with sulfur and its oxides ejected

* See: I. Mitrofanov, "Unlocking Martian Enigmas", Science in Russia, No. 6, 2002.- Ed.

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from the interior of this small planet (having no atmosphere) as high as 300 km. Possibly, it was water and chlorine that oxidized sulfur in this rather odd process. Today sulfur blankets as much as 70 percent of lo's surface, and sulfates-30 percent.

Yet the solar system has no lo's analogs, nor Mars is like it. The Martian ferrous crusts of weathering, 4 to 5 km thick and even more, detected in some of the sections of gully banks, indicate-may I repeat it again-the presence of a large oxygen atmosphere in the past, and hence of a plant kingdom.

Unlike the ferrous red rocks of the earth, the Martian red sands are found to be magnetic! This striking phenomenon may be explained as follows: though identical in their chemical composition (Fe ₂ O ₃ ), they have different pigments. Here on earth this is the mineral hematite (from the Greek haematos, or blood) with admixtures of limonite, or brown hematite (iron hydroxide); but the Martian sands are stained by maghemite, the red magnetic oxide of iron which has the same chemical composition as hematite, though its crystal structure is the same as of the magnetic mineral magnetite.

Hematite and limonite are among the widely occurring iron ores, while maghemite is rare and formed by the oxidation of magnetite which preserves its primary crystal structure and magnetic properties. Heated above 200C, magnetite turns into hematite and loses its magnetism. Yet industry is producing large amounts of synthetic maghemite by calcinating the hydroxide of iron (analog of native limonite) at 800 to 1,000C. This product is used as sound recording material in magnetic tapes and stains them red and brown. This kind of iron oxide is magnetic, and retains this characteristic in repeat calcination.

Maghemite occurs but rarely on earth. Yet as I have found, the territory of Yakutia is really "strewn" with it. Searching for kimberlite (diamond) pipes, we had to study the many "false" magnetic anomalies quite similar to those indicating the presence of such pipes, though related to a concentration of magnetic oxide of iron either in the form of reddish sand or debris, the concretions of varying size. The maghemite thus detected retained magnetism even after calcination, in much the same way as does its synthetic analog. I have described it as a new mineral variety, the "stable maghemite". Then came the questions: Why is it like the artificial magnetic oxide of iron? And why is it in such abundance in Yakutia, but is not found among the numerous red rocks of the equatorial zone?

The commercial production of the red magnetic oxide of iron has shown the pathway of stable maghemite formation: calcination of native limonite crusts of weathering of which plenty are found in Yakutia's old sedimentary rocks. Well, but how could they be calcinated under natural conditions? Because of forest fires, when blazing trees fall to the iron-containing ground?.. Yet the same thing is

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taking place in the equatorial latitudes with little, if any, of the magnetic oxide of iron. In Yakutia, however, it is widespread over a vast territory, with rivers washing it out of old deposits. But what if some powerful flux of energy calcinated the entire surface of Siberia's northeast, where Yakutia lies?

A sensational discovery may help solve this puzzle: a giant meteorite-struck crater, 130 km in diameter, saddling the river Popigai basin in eastern Siberia's northwest. The disastrous impact occurred about 35 mln years ago. It might be responsible for the transition of two geological epochs, Eocene and Oligocene (ca. 30 mln years ago) when the animal kingdom experienced dramatic changes.

The cosmic impact was terrific. The asteroid's diameter was 9 to 10 km, its mass-as much as 3 mln tons, and velocity-20 - 30 km/s. It pierced the atmosphere and, hitting the ground, melted 4 - 5 km ³ of rock, jumbling together basalts, granites and sedimentary deposits. The cosmic flames scorched the surface over hundreds of kilometers, killing every living breath there. The water of rivers and lakes evaporated.

The blast produced minerals which can be formed only at "extraterrestrial" pressures of hundreds of thousands of atmospheres. These are the heavy modifications of silica, coecite and stishovite, and the hexagonal modification of diamond, lonsda-leite. These minerals are actually absent in native rock-the pressure is all too low for their formation. The Popigai caldera, however, is the world's largest deposit of diamonds, though not of cubic ones found in kimberlites, but of hexagonal structure; unfortunately the low grade of these crystals forbids their use even in industry. The scorching of red limonite crusts of weathering concurred with the conversion of iron hydroxides into stable maghemite.

The anomalously wide occurrence of magnetic oxide of iron in Yakutia holds a key to the enigma of the magnetism of red crusts of weathering on Mars. That planet has over a hundred giant calderas formed by the impact of meteorites-craters larger than Pagai; as to the smaller ones, they are too many to be counted. So the Red Planet has caught it: the presence of liquid water eroding fast the calderas and craters is suggestive of the relatively young age of many of them.

The Martian surface was thus badly scorched by cosmic flames, a process that caused magnetization of ferrous detritus. That is why the concentration of maghemite in the Martian ground is up to 5 - 8 percent. Sulfates might have been formed with the evaporation of salt lakes and shallow maria (seas), even though sulfur dioxide (sulfurous gas) could have also been ejected by volcanoes, now dead. The present rarefied atmosphere may also be a sequel to the asteroid attack: at high temperatures gases turn into plasma escaping into the void. The oxygen of the Martian atmosphere is of relict nature-the miserable amount of what was once produced by Martian life and what was wiped out by asteroids.

Calcination and magnetization of the originally nonmagnetic ferrous detritus involved a fantastic expense of energy tantamount to what is released by several million powerful hydrogen bombs. Such kind of holocaust would have wiped out life on earth too: its atmosphere would have become rarefied and unfit for respiration; while the death of the plant kingdom would have resulted in the further disappearance of oxygen. But Mars is a planet much smaller than earth, and it has a weaker gravitational pull. The cosmic "shelling" obliterated its plant life, while plasma fluxes tore off its oxygen atmosphere and magnetized its red crusts of weathering. The planet turned into a barren waste with frozen maria and rivers buried under red magnetic sands.

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