On the occasion of the fourth anniversary of the landing of the Mars Curiosity Rover talk about our current knowledge about Mars together with the newspaper “Troitsky variant – science”.
Planeta Shelezyaka: no water, no minerals, inhabited by robots…” it looks Like Mars, but matches only the item with the robots, the rest is there, though not as much as on Earth. What about Mars is well known? The fourth planet from the Sun. Less Land, more mercury. The volcano Olympus, the largest in the Solar system the mountain, it is also the biggest volcano. Valley of the Mariner — the largest in the Solar system, a canyon that is hundreds of times more than the biggest canyon on Earth.
Global dust storms. Thin carbon dioxide atmosphere. Red color due to iron oxides that cover the surface. I think this is the minimum that knows or should know of the neighboring planet, the vast majority of the inhabitants of the planet Earth.
However, the study of Mars continues, new facts and discoveries are announced regularly on almost every planetological research conference. Will try to update our knowledge and together with it the freshness and fullness.
Let’s start with the atmosphere. Despite its sparseness, the atmosphere is the “live” part of Mars, where many interesting processes. The atmospheric density of Mars is an average of 1/125 second part of the density of Earth’s atmosphere. While its thickness is slightly inferior to the thickness of the Earth’s atmosphere — this is due to the lesser gravity. Therefore, research satellites earthlings have to fly at altitudes above 250 km, so the atmosphere had a significant effect on the orbit.
The global Martian dust storms are irregular and occur approximately every 6 earth years. At the same time every Martian year the atmosphere is experiencing a large-scale evaporation processes of carbon dioxide polar cap in the summer hemisphere and freezing of the same hat at the winter pole of the planet. In this involved pumping up to a quarter of the entire mass of the atmosphere.
Such dynamics gives rise to local storms which are frequent at the poles, but rarely get to the equator. For example, the Mars Rover Curiosity working in 5 degrees South of the equator only once in two days was in the dust, limiting visibility to ten kilometers. At other times visibility up to 40 km, and in some quiet winter weeks you can see the tops of the mountains at a distance of 80 km.
Almost any time of the year in the atmosphere of Mars hanging red dust, although depending on the time of year the concentration is changing. The “dusty” times — autumn and spring, when there is a pumping atmosphere from one pole to the other. At this time, the sky color is orange beige up to brown during storms. In quiet months, the dust settles, Zenith black, and beige color of the sky down to the horizon. At this time it is possible to observe the bluish hues of the sky when the sun is approaching the horizon, and atmospheric gases time to dissipate a bit of the blue component of the solar spectrum.
In addition to large-scale dust storms covering the entire planet or significant parts of it, on Mars we can observe the activity of small vortices, which American scientists call the Dust Devil. Often they look like a dusty trunk, rising to a height of several meters to several hundred meters.
Dust Devil may be invisible. For example, sensors of atmospheric pressure, Curiosity has repeatedly recorded the passage of a small vortex at the apparatus, at the same time, no camera could never pull off such a whirlwind, although attempts are being made regularly. But the Opportunity periodically to see small vortices, which also help to clean its solar panels from dust.
Due to frequent dust storms someone could form the impression that Mars just the eyeballs littered with dust, which makes it impossible to study its Geology in situ in place. Inches drill last Rover for many it is surprising for its short length. Dust, of course, on Mars covers the entire space, which could reach wind, but the thickness of the dust layer often does not exceed a fraction of a millimeter. The process of atmospheric erosion on Mars is still ongoing, it increases the volume of the dust, but the surface areas exposed to erosion, bare. In one of these places just Curiosity works.
A good argument in favor of low-intensity deposition of weathering products can serve as an example of a parachute landing modules of automatic space stations of the last century. In 2012, we managed to find the parachute “Mars-3” (1971 planting), and then the unit itself.
Documented parachutes stations Viking-1 (1976) and the Mars Pathfnder (1997). Hidden under layers of dust, you can recognize the parachute Viking-2, and did not manage to detect the signs of a parachute “Mars-6”, although repeated attempts were made.
Dust in the atmosphere can be distributed in multiple layers, forming clouds, including high-rise, and to rise to heights not less than 50 km or even higher by several tens of kilometers.
Often in the media are confusing the dust and sand. It’s on Earth possible sand storms and the migration of sand for hundreds of kilometers. For Mars is relevant only for dust particles the size of which does not exceed 0.1 mm. larger sand, the wind also moved, but a few centimeters up to a meter in the course of the year.
On Mars, carefully studied volcanic crater Nili Patera, the bottom of which “creep” the sand dunes. They moved for many years, monitored with the high resolution camera HiRise satellite MRO. The movement of sand dunes found in other areas of Mars.
Another interesting object to study are the polar ice caps. Polar ice is, perhaps, the first objects on the surface of Mars, which was determined by the people. When the astronomers saw the similarity of the poles of the Earth and Mars, and then saw dark spots on the sides of the red planet, Mars, has shown a full copy of the Earth, and the idea about the locals was quite logical.
At first, the polar caps of Mars were considered for the water and their annual variability gave rise to hypotheses about the regular floods of melt water, which is superimposed on the erroneous observation of Martian “canals”. However, in the mid-twentieth century failed to establish that the main area of the winter poles closes the carbon dioxide ice and the water remains in the small area, the summer polar caps. Thanks to the MARSIS radar of the satellite Mars Express was able to establish the power of polar water deposits: in the North — 1.7 km on South to 3 km If you take the polar ice to melt, it will entirely fill with water height of 21 m is a smooth planet the size of Mars. Accordingly, if the melt these stocks, on a small pond or a few small seas of Mars is enough for us.
Studies of the Martian surface indicate that the water was more. The planet observed the empty river bed, river deltas, remains of lakes, and there are even some signs of a former ocean, occupying from a quarter to a third of the entire planet. The question is, where were a vast inventory of Martian water, does not yet have an exact answer, but there are two hypotheses: the first is water left in the ground, contacted minerals and formed a groundwater glaciers; the second, water disperable into space. Although more arguments inclines to the second hypothesis, water on Mars is not only at the poles and in the circumpolar region. Subsurface glaciers are defined in the Northern hemisphere to the 40’s Parallels to the equator — for the Earth is the latitude of Sochi. There are deposits of ice to the East from the valley of Hellas, and even at the equator, the water content is from 5% to 10% in the soil.
All this time we talked about water in the solid phase or in the related aggregate condition. The atmospheric pressure of Mars is not conducive to maintaining water in the liquid phase even in the lower regions with the highest pressure water boils already at +10 °C, and given the seasonal variation in atmospheric density and temperature over +10 °C in summer days, the long-term conservation of water on the surface is virtually eliminated. But recent studies of hyperspectrometer CRISM and HiRise camera added to the arguments the hypothesis that the Mars soil capable of sustaining water in liquid state at zero temperature in the form of brines of salts of perchloric acid.
Until recently, scientists could not give an affirmative answer to the question about the presence of organic compounds on Mars. The first data appeared in the ground observations, when it is determined the presence of methane in the Martian atmosphere. For the search of organics on the Red planet went Curiosity Rover. The first data at the end of 2012 was encouraging, but then it turned out that an error occurred and the Rover found organics, which he himself had with him and took — damage the capacity of the solvent to “wet” soil analysis. In a year when the machine has accumulated statistics of studies of different types of soils, were able to speak more confidently — organic is. Were found chlorobenzene.
A year later was able to confirm the appearance of methane in the Martian atmosphere, although the processes that are causing the allocation of this gas, while there is no unequivocal opinion.
Note that found organic compounds are not the direct proof of the existence in the past of Mars biological activity. Organic compounds known on mercury, comets, asteroids, satellites of the giant planets, the atmosphere of the planets-giants and other places near and far Universe. To identify biomarkers in organic compounds of Mars will be able mission of the ExoMars Rover, whose launch is planned for 2020.
An important finding from the point of view of possible past or future life — nitrates in certain geological layers in Gale crater. For Earth nitrates are considered a fertilizer and is used as directed. For Mars was found nitrates indicate that in the past were the conditions on which to develop the known life forms, and this finding opens perspectives for the future of farming (or rather, martelia) and agriculture.
Analysis of the Martian soil, carried out by the SAM mass spectrometer on Board the Rover Curiosity, has shown that heating the soil to 400 °C, carbon dioxide, water vapor, oxygen and nitrogen that, in General, suitable for use in a future human activities on Mars.
In the context of a manned mission to Mars in mandatory raises the question of radiation hazard during the flight and when working on the surface. Study of radiation environment during the flight to Mars and on its surface were done and carried out by the RAD instrument on Board the Curiosity Rover.
To study the effect of cosmic rays during the flight to Mars have not yielded very encouraging data: the risk for people more than half valid for the astronauts, for astronauts tolerances are even more severe. On the surface, conditions are more acceptable. The impact of ionizing particles on the surface of Mars is approximately twice lower than in the conditions of space flights, and at low solar activity corresponds to the background radiation on Board the International space station.
Mandatory step in the exploration of Mars will be a delivery to the Earth samples of a ground. While this task is difficult enough, but remains in the project, NASA and Roskosmos. While it is possible to study meteorites, which are believed to come from Mars. In the 1990-ies it was reported that one of the meteors found fossils similar to bacteria, but most scientists have challenged this hypothesis. Recently curious fossilized structure was discovered by in another meteorite.
Externally, the discovery is like a cage, where you can define even cellular vacuoles and pores, but so far this is an isolated incident and too little actual data to Express the sensation. We can only hope for more fruitful discoveries of present and future research missions.
