Secrets of the red planet

More than a thousand years later, the Greeks called these celestial bodies as wanderers - planhtai; later this word entered Latin (plural - planetai, singular - planeta), and then into other European languages. One of the planets has a clear reddish tint, so many people called it Red or Fiery. Following the Babylonians and Egyptians, the Greeks began to give the planets additional names dedicated to deities, and the red planet acquired the name of the god of war Ares. In the Roman pantheon, it was called Mars.

View from the outside

Until the invention of the telescope, all astronomical information about Mars was limited to a description of its motion in the celestial sphere. At the end of the 16th century, Danes Tycho Brahe made measurements of unsurpassed accuracy, and Johannes Kepler formulated the laws of planetary motion on the basis of this information. In 1636 and 1638, the Italian Francesco Fontana was the first to sketch the phases of Mars, which Galileo actually observed. In 1659, Christian Huygens estimated the diameter of Mars and the duration of its day, and in the first case it was only 10% mistaken, and in the second - less than 5%. A few years later, Giovanni Cassini calculated the then distance from Earth to Mars and determined the length of his day with just a three-minute error. The same Cassini, and then his nephew Giacomo Maraldi noticed white spots at the poles of Mars, but did not say that it was snow or ice. The great English astronomer William Herschel ventured into this for the first time in 1781. He also measured the inclination of the axis of Mars to the plane of the ecliptic and hypothesized that this planet exists in the atmosphere.

The first more or less accurate map of Mars, compiled according to astronomical observations during the years of the closest approach of the Red Planet to the Earth (1877 and 1881). True, highlands and valleys at that time were considered seas and continents.

After Herschel’s work, for about half a century, interest in Mars somehow faded and revived only in 1830, when Mars and Earth once again approached each other at a minimum distance. In the following decades, astronomers began to map Mars, and one of them turned into a world sensation. This map, based on his own sketches made during the rapprochement of 1877, was drawn by the Italian Giovanni Schiaparelli. His map contains many dark intersecting lines, which the scientist called canali. This is the plural of the Italian word canale, which means a natural waterway, in particular - a river bed and a sea channel. However, in most translations this meaning was lost, and Schiaparelli's structures began, without further ado, to be called simply channels. And so a legend arose about the presence of artificial waterways on Mars, which Schiaparelli never claimed. It should be noted that at least ten other astronomers observed the same lines before him, which Schiaparelli repeatedly emphasized.

Great confrontations between the approach of Mars to the Earth are observed when both planets are on the same side of the Sun. The distance between them can vary significantly depending on the position of the planets (aphelion and perihelion).

Belief in the Martian channels lasted another thirty years, and then gradually died a natural death. At the beginning of the 20th century, astronomers who already had very powerful telescopes could not see them either visually or in photographs. At the same time, spectrographic studies of Mars convincingly showed that there is no liquid water on the planet. What exactly Schiaparelli and his contemporaries saw is still not clear, but in all likelihood, they were victims of an optical illusion.

Mars in motion

Mars revolves around the Sun in a very distinct ellipse. In this, it is very different from such planets as Venus, Earth and Neptune, whose orbits are almost circular. At perihelion, it is 206.644 million km away from our luminary, and at aphelion it is 249.229 million km away. According to the eccentricity (degree of elongation) of the orbit, Mars takes third place among the planets of the solar system, second only to Pluto and Mercury (and if Pluto, in accordance with a recent decision of the International Astronomical Union, is excluded from the list of planets, then even the second). The duration of his year is 687 Earth days. The Martian axis is inclined to its orbital plane by about 25 degrees - a little more than the earth. The Martian day also differs little from the Earth - 24 hours 37 minutes. Since Mars and the Earth go around the Sun at an unequal pace, the distances between them periodically change. The planets approach each other when Mars passes through the perihelion, and the Earth passes through the aphelion, both planets being on the same side of the Sun. On average, such situations occur every 780 days. The closest approach of the planets to each other is called the great confrontation. Great confrontations occur once every 15-17 years. Since the orbits of Mars and the Earth lie in different planes (the angle between them is about two degrees), the distances between the planets during various great confrontations are not quite the same. In 1830, they were 58.12 million km from each other, in 1877 - 56.41 million km, in 2003 - 55.76 million km.

However, in 1877 a genuine discovery was made. American astronomer Azef Hall using the 26-inch telescope-refractor of the Naval Observatory discovered two small satellites in Mars - Phobos and Deimos.

The first six decades of the twentieth century brought a lot of information about Mars. So, in the 1920s, the Americans Seth Nicholson and Edison Pettit were the first to determine the temperature of the Martian surface. Naturally, the mapping of Mars continued with the use of more and more advanced telescopes and cameras. However, the true rise of Martian astronomy began only in the space age.

On a date with Mars

The red planet turned out to be a tough nut for world cosmonautics. From 1960 to 2007, 38 automatic vehicles went to Mars: 19 American, 17 Soviet and Russian, one European and one Japanese. Only NASA projects were successful, and even then not all. Twelve flights to Mars and to Mars met expectations, six failed; the fate of the Phoenix ship, which launched on August 4, 2007 from Cape Canaveral, is too early to discuss. The overall balance is: 25 unsuccessful attempts, 12 successful, one ship on the way.

Atmosphere and climate Even 60 years ago it was believed that the Martian atmosphere consists mainly of nitrogen. It was only in 1947 that Gerard Kuiper found out that its main component is carbon dioxide. Space probes made it possible to establish the composition of Martian air: 95.3% CO2, 2.7% nitrogen, 1.6% argon, 0.2% molecular oxygen, traces of ozone, nitric oxide, methane, formaldehyde, neon, krypton and xenon. The axis of Mars is inclined to its orbital plane at almost the same angle as the Earth's, and the seasons there follow the Earth's pattern (but the seasons are almost twice as long). In summer, the daytime temperature reaches + 300С, and in winter it drops to -1400С - much lower than the freezing point of carbon dioxide. The poles of the planet are covered with ancient shields of water ice. In winter, solid carbon dioxide crust freezes on them, which evaporates under the rays of the summer sun. Therefore, in the summer seasons, hurricane winds blow from the poles at a speed of up to 400 km / h. Seasonal precipitation and evaporation of CO2 leads to the fact that each year 25-30% of the Martian atmosphere migrates from pole to pole. Therefore, dust storms rage on Mars year-round, throwing a myriad of micron-sized particles into the air. Due to the relatively low gravity and almost zero humidity, dust particles penetrate high into the atmosphere, staining the Martian skies with reddish-brown tones.

The first launches of space probes to Mars were made from the launch complex No. 1 of the Baikonur Cosmodrome on October 10 and 14, 1960. Both of them failed: before launching into the intermediate near-Earth orbit, a booster rocket exploded. The three launches of 1962 were also contingencies. The ships that started on October 24 and November 4 reached the near-Earth intermediate orbit, but could not reach the calculated interplanetary trajectory. The 900-kilogram Mars-1 station, which went into space on November 1, circled the Red Planet at a distance of 197, 000 km on May 19 of the following year (after which it entered a near-solar elliptical orbit), however, three months before the flight with Mars-1, it was lost communication. A similar fate befell the station Zond-2, launched on November 30, 1964. This failure turned out to be particularly annoying, since the ship was only 1, 500 km from Mars and could collect unique information.

It is possible that millions of years ago, Mars was covered with water (below). But weak gravity, a thin atmosphere and a weak magnetic field of the planet led to the fact that liquid water escaped into outer space (in the center and left)

The chronicle of the later Martian launches from Baikonur looks like a repetition of the past. On November 27 and December 2, 1971, the Mars-2 and Mars-3 stations entered orbits around Mars and sent descent vehicles to its surface. One of them crashed, and the other after a soft landing worked for only 20 seconds. In 1973, Mars were launched with numbers 4, 5, 6, and 7. Two of them passed the planet, sent signals from the near-Martian orbit for several days, and then fell silent forever; "Mars-6" landed and disconnected. In July 1988, two stations that were supposed to land on Phobos, but also lost contact with them, went into space. On November 16, 1996, the last of the Mars (numbered 8) fell victim to the launch vehicle accident.

Mars is almost half the size of Earth. Its polar and equatorial radii are 3357 and 3397 km (53% of the corresponding Earth dimensions), the volume is 15% of the Earth’s volume, and its mass is only 11%. It follows that the average density of Mars is much lower than the density of our planet (3.94 against 5.52 g / cm3). Martian areography is now well known. The southern hemisphere of the planet is noticeably higher than the northern and dotted with hundreds of thousands of meteorite craters. There are few craters in the north, but there are the main volcanoes there, now inactive. Among them is the 27-kilometer giant Olympus, the highest of the mountains of the solar system. The giant tectonic fault Valles Marineris (Mariner Valley) with a length of more than 4000 km (about 0.2 of the circumference of the planet) and a depth of 7-8 km is also located in the northern hemisphere. Mars, like Earth, has a core, mantle and crust. According to the latest data, the core diameter is 1480 km. It consists of 85% iron, the rest is sulfur and nickel. The core is surrounded by a mantle, which is most likely composed of silicon, oxygen, iron and magnesium. Above it is a basaltic crust, the thickness of which lies within 50−125 km.

The United States began expeditions to Mars with two ships of the Mariner series, launched in November 1964. The first could not reach the calculated trajectory, and the second, Mariner-4, on July 14, 1965 passed 9920 km from Mars and transmitted 22 images of its surface to Earth. Of course, there were no canals or other bodies of water on them. The ship did not find a magnetic field in Mars.

Water on Mars There is no liquid water on Mars. Almost all of it is in a solid state (ice) deep below the surface in the polar regions of the Red Planet. The figure shows a diagram of one of these ice "pockets" in the crust of the planet.

In 1969, Mariner-6 and Mariner-7 flew past Mars, which took 202 photographs covering 9% of the Martian surface. The more advanced Mariner-9 entered orbiting Martian orbit and became the first spacecraft to become a satellite of another planet. This happened on November 14, 1971 (the device was ahead of Mars-2 by only 13 Earth days). And on July 20 and September 3, 1976, the Viking-1 and Viking-2 ships sent stations with scientific equipment to Mars. The first of them was valid until November 13, 1982, the second - until April 11, 1980. From these stations, panoramic images of the Martian surface and not so sensational, but extremely useful information about the features of Martian geology (more correctly, areology) and the atmosphere were obtained.

Three-dimensional map of Mars, obtained using a laser altimeter aboard the Mars Global Surveyor satellite. To capture this map, 27 million measurements were taken with an accuracy of about 13 m. Giant volcanoes are visible in the right hemisphere.

On the dusty paths

July 4, 1997 on the Martian surface sank the American ship Pathfinder. He brought the world's first Mars rover - a small (only 10.5 kg) six-wheeled SUJ Sojourner. This friendly couple did not work long (the last communication session took place on September 27), but very productively. She took more than 17, 000 photographs, performed a chemical analysis of two dozen samples of soil and rock, and collected a large amount of information about the air basin of the planet. And on September 11, another orbital probe, the Mars Global Surveyor, began to work, equipped with a camera, a laser altimeter, a magnetometer, and an infrared spectrometer. He completed the entire initial program by the beginning of 2001, but remained in office for more than five years until the termination of communications on November 2, 2006.

Currently, four NASA envoys and one ESA are exploring the Red Planet. From space, American stations Mars Odyssey and Mars Reconnaissance Orbiter and their European partner Mars Express Orbiter are watching her. Since January 2004, the American rovers Spirit and Opportunity have walked on its surface. By mid-October 2007, the first device passed a little more than 7.25 km and sent 102, 000 photos to Earth. The second took 94, 000 pictures, but then drove over 11.5 km. If nothing happens, then on May 25, 2008 they will be joined by the stationary descent vehicle of the Phoenix ship, equipped with an automatic excavator. It will mine subsoil ice and transmit it for analysis to airborne instruments.

Near-Earth observatories (primarily the Hubble orbital telescope) and the latest ground-based telescopes and radio telescopes also study Mars. Therefore, astronomers today know about it much more than just three or four decades ago. But the question “Is there (or was) life on Mars?” Still has to be answered with a quote from the famous film by Eldar Ryazanov: “This is unknown to science.”

The article was published in the journal Popular Mechanics (No. 12, December 2007).


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