Recently published images of direct observations of ice layers under the surface of Mars in mid-latitudes. We tell a brief history of Martian water and the latest news in conjunction with the popular science portal “Attic”.
The presence of water on Mars for a long time is not a secret. Already now the water ice reserves at the poles have been roughly estimated, glaciers have been found in middle latitudes; it is known that even in the equatorial soil of the red planet the concentration of water in some places reaches one tenth. However, most of the data on the water content on Mars was obtained using radar or neutron spectrometers. But actually it is rarely possible to look at the Martian ice. And just recently a similar meeting took place: the HiRise orbital telescope aboard a Mars Reconnaissance Orbiter managed to photograph ice deposits on the slopes of ravines in middle latitudes, and scientists were able to look at Martian glaciers for the first time in profile.
Astronomers examined the polar ices of Mars already in the 19th century – these are one of the most conspicuous parts of its surface. However, in the past centuries of astronomy, it was believed that the poles of the red planet covers only frozen water. While optical devices were not of high quality, many gaps in knowledge about the neighboring planet had to be closed with earthly analogies and optimistic expectations. It was from these expectations that the illusion of the Martian canals grew, which lasted until the very beginning of the space age. Astronomers could argue about the origin of the channels, artificial or natural, but most did not doubt their existence.
Mariner 4 image borders on Mars map
Cross on the fate of the Martian channels put the probe NASA Mariner 4, which in 1964 for the first time took pictures of sufficient quality of the surface of the planet from close range. The landscapes opened to the researchers destroyed all hopes for the “land-likeness” of Mars. In 1973, the Soviet Mars-5 orbiter transmitted the first color images – these were photographs of the red, waterless and lifeless desert.
Photo of the surface of Mars from the Soviet Mars-5 orbiter
In 1976, the Viking 1 and 2 landing gears took soil samples and determined the water content in it – no more than 3%. By that time, it was already known that the seasonal variability of polar ice and the growth of polar caps in winter are determined not by water, but by “dry” carbon dioxide ice. And the white spots on the poles, which do not change over the course of the year, are the second layer of ice, already water.
polar cap of mars
The re-discovery of Martian water began in 2002, with the launch of NASA’s Mars Odyssey satellite into the working orbit of the fourth planet. An integral part of his GRS instrument was the Russian HEND neutron spectrometer. By registering the speed of neutrons emitted from the ground of Mars under the impacts of cosmic particles, HEND determined the concentration of hydrogen, which slows down the neutrons. Hydrogen in free form cannot be contained in the soil of Mars; therefore, its detection in the soil would make it possible to assume the presence of water or water ice there. By 2007, a complete map of the distribution of water in the surface layer up to 1 meter deep was built – unfortunately, it was impossible to look deeper using neutron spectroscopy. Data even about the shallow distribution of water turned out to be unexpected for many – water was found.
According to HEND, the concentration of water in the surface layer at the equator is about 5% and towards the poles is constantly increasing, reaching 90%. In 2008, the results of orbital sensing were confirmed already from the surface by the Phoenix landing module. The device sat on the high 68th latitude of the northern hemisphere. Digging the ground, Phoenix found frozen water just a few centimeters from the surface.
Phoenix device found frozen water on Mars
In 2006, the SHARAD radar was added on the NASA MRO satellite, and in 2007 the MARSIS radar was added on the Mars Express European satellite. They were able to “shine through” the depths of Mars at depths of up to 3 km and not only detect the layers of ice below the surface, but also find out the power of the polar caps. It turned out that the South Pole of Mars was covered with 3.5 kilometers of water ice, and the North – with 1.7 kilometers. If you melt this water, then the ocean could flood the entire planet to a depth of 21 m (if you do not take into account the relief and elevation). And this is not the limit: at one time, the waters on the now “withered” Mars were 6.5 times more.
The MRO has the most long-range camera that has ever reached Mars. HiRise telescope provides shooting with a resolution of up to 25 cm, so that it could be used to see its “inhabitants” – descent vehicles and mars rovers. In his photographs, the Mars-3 lander was found, he was able to tell HiRise and more about the Martian water. Observation of the steep edges of the polar caps made it possible to study their layered structure and see the real extraterrestrial avalanche.
ice avalanche on mars
It turned out that similar processes did not freeze in a thin Martian atmosphere, and not only carbon dioxide ice, but also water ice were affected.
Even more interesting results were obtained by observing middle latitudes. Meteorites continue to fall on Mars, and fresh craters in seemingly desert plains expose the ice beneath the surface.
ice on mars in fresh meteorite craters
If Viking 1 could dig half a meter deeper, he would have found a whole layer of ice. Radar sounding in latitudes 40–60 ° showed extensive deposits of ice at depths of up to 1 km. According to some estimates, these stocks make up to 5% of the volume of polar caps. Especially extensive reserves of ice are observed east of the Hellas valley, near the Greg crater.
ice deposits on Mars as a result of radar sounding
The origin of these deposits is curious. Analysis of the nature of ice deposits in polar caps led the researchers to the hypothesis that Mars repeatedly changed the inclination of its axis, deviating by 40 ° from the current 25. At some periods, the North Pole of Mars turned directly to the sun, which led to its active evaporation. The result was an increase in the density of the planet’s atmosphere, dust storms and heavy snowfall. Climatologists have applied the Earth’s climate model to a similar scenario of Martian life and obtained data on heavy snowfall east of Hellas.
Finally, the result of direct observations of deposits of Martian ice in mid-latitudes was recently published. Attentive analysis of HiRise images allowed scientists to find several cliffs, in the slopes of which white and bluish layers of ice are clearly visible.
layer of naked martian ice
An additional CRISM hyperspectral test on the same MRO confirmed the presence of water.
hyperspectral analysis of ice deposits
The observed ice deposits start from a depth of about 1 m and reach a thickness of 130 m. They alternate with layers of soil, apparently brought during seasonal dust storms. Most of the detected ice slopes were found east of Hellas.
ice slopes on a map of mars
The study of these layers can tell more about the climate history of Mars. In addition, it is now clear that the future conquerors of the Red Planet will not have to extract water, following the example of the hero of the fantastic film The Martian, from rocket fuel. There are enough buckets and shovels on the ground, and water can be used just for fuel production and return home. True, medium latitudes are not the best place to land – it is too cold.
A series of shots with a difference of three Martian years made it possible to see some changes in the shape of the cliffs. Apparently, as in the case of the polar glaciers, the melting processes continue, and the slopes slowly evolve.
What is even more interesting is that all these frozen deposits appeared not billions of years ago, but more recently by geological measures. If you take a broader look at the once snow-covered, and now open spaces covered with sand and dust, you can marvel at their virginal purity – there are almost no meteorite craters.
Photo of the surface of Mars from the satellite
This means that the period of the turbulent Martian atmosphere and snowstorms on a planetary scale ended quite recently. According to modern estimates, the near-surface glacial deposits in the middle latitudes of Mars formed 10-20 million years ago – for the life of the planet, it was not even yesterday, but a minute ago. It is hoped that this will happen in the future – a dense atmosphere would greatly simplify the process of colonization.
In 2018 Mars will launch the European-Russian satellite ExoMars Trace Gas Orbiter. On board is a FREND instrument, which operates on the HEND principle, but with a higher spatial resolution. He will not be able to look deeper than 1 meter into the ground, but he will be able to map the surface deposits of ice with much higher accuracy, which will allow to study water reserves on the Red Planet in more detail and to plan future automatic and manned missions more precisely.