What is the climate on Mars?
The climate, as on Earth, is seasonal.
Mars perihelion occurs during the height of winter in the northern hemisphere and summer in the southern hemisphere, and aphelion occurs during the height of winter in the southern hemisphere and summer in the northern hemisphere.As a result, the climate of the northern and southern hemispheres is different.
The northern hemisphere is characterized by a softerwinter and cool summer; in the southern hemisphere, winters are colder and summers hotter. In the cold season, light frost can form on the surface even outside the polar caps. The Phoenix spacecraft recorded a snowfall, but the snowflakes evaporated before reaching the surface.
According to NASA (2004), the average temperatureis ~ 210 K (-63 ° C). According to the Viking lander, the daily temperature range is from 184 K to 242 K (-89 to -31 ° C) (Viking-1), and the wind speed is 2-7 m / s (summer), 5 -10 m / s (autumn), 17-30 m / s (dust storm)
The shock depression Hellas is the deepest place on Mars, where the highest atmospheric pressure can be recorded
According to the Mars-6 landing probe, the averageThe temperature of the troposphere of Mars is 228 K, in the troposphere the temperature decreases by an average of 2.5 degrees per kilometer, and the stratosphere, located above the tropopause (30 km), has an almost constant temperature of 144 K.
In 2007-2008, researchers from the Carl Sagan Center concluded that in recent decades there has been aNASA experts confirmed this hypothesis based on the analysis of changes in the albedo of different parts of the planet.Other experts believe that it is too early to draw such conclusions.
In May 2016, researchers from the South-WestResearch Institute in Boulder, Colorado published an article in Science, which presented new evidence of ongoing climate warming (based on the analysis of data from the Mars Reconnaissance Orbiter). In their opinion, this process is long and has been going on, perhaps, for 370 thousand years.
There are suggestions that in the past the atmospherecould be denser, and the climate warm and humid, and liquid water existed on the surface of Mars and it rained. Proof of this hypothesis is the analysis of the meteorite ALH 84001, which showed that about 4 billion years ago the temperature of Mars was 18 ± 4 ° C.
The main feature of the general circulation of the atmosphereMars are phase transitions of carbon dioxide in the polar caps, leading to significant meridional fluxes. Numerical modeling of the general circulation of the Mars atmosphere indicates a significant annual pressure variation with two minima shortly before the equinoxes, which is also confirmed by observations from the Viking program.
Analysis of the pressure data revealed annual and semi-annual cycles.Interestingly, as on Earth, the maximum semi-annual fluctuations in zonal wind speed coincideNumerical simulations also reveal a significant index cycle with a period of 4-6 days during the solstices.Viking has discovered a similarity of the index cycle on Mars with similar fluctuations in the atmospheres of other planets.
Where does water and ice come from on Mars?
Mars is very similar to Earth in many ways, which led scientists in the 19th and early 20th centuries to assume that there is life and liquid water on it.
As the amount of data about the planet collected by various methods, such as spectroscopic measurements, has grown, it has become clear that water in the Martian atmosphere is negligible, but it is still present.
First of all, the attention of the researchers was attracted by the polar caps of Mars, since it was assumed that they couldIt is composed of water ice by analogy with Antarctica or Greenland on Earth, but it has also been hypothesized that it is solid carbon dioxide.
The results of one of the first numerical experiments in 1966 on the IBM 7074 computer to simulate daily and annual temperature changes on the surface of Mars depending on thelatitude and the corresponding dynamics of the polar caps for cases where they consist ofThe authors of this study concluded that their annual variation in the size of the polar caps in the second case is much closer to the observed one.
Lambert Equal Area Azimuthrelief of the surface of Mars from the North Pole to the equator, filmed by the MOLA altimeter [en]. The border of the Northern Lowland strongly resembles the coast of the ocean, which may have covered this area in ancient times.
Water reserves on Mars
- Ice
At present, the discovered and reliably established volumes of water on Mars are concentrated mainly in the so-called cryosphere, a near-surface layer of permafrost tens and hundreds of meters thick.
Most of this ice is under the surface of the planet, as it cannotexist stably and, once on the surface, evaporates quickly; Only in the circumpolar regions is the temperature low enough for the stable existence of ice throughout the year – these are the polar caps.
The total volume of ice on the surface and inthe near-surface layer is estimated at 5 million km³ (and in deeper layers, probably much larger reserves of subpermafrost salt water can be concentrated. Their volume is estimated at 54-77 million km³). In a molten state, it would cover the surface of Mars with a layer of water 35 m thick.
- Liquid
On July 25, 2018, a report on the discovery was released,based on MARSIS radar research. The work showed the presence of a subglacial lake on Mars, located at a depth of 1.5 km under the ice of the South Polar Cap, about 20 km wide. This became the first known permanent body of water on Mars.
Probing an area about 200 kilometers wideusing MARSIS showed that the surface of the South Pole of Mars is covered with several layers of ice and dust and a depth of about 1.5 kilometers. A particularly strong increase in signal reflection was recorded under layered sediments within a 20-kilometer zone at a depth of about 1.5 kilometers.
Having analyzed the properties of the reflected signal andAfter studying the composition of the layered sediments, as well as the expected temperature profile below the surface of this area, the scientists concluded that the radar had detected a pocket of liquid water beneath the surface.
The device could not determine how deepthere may be a lake, but its depth must be at least several tens of centimeters (the layer of water must be such that MARSIS can see it).
How does climate change on Mars?
The appearance of Mars varies greatly depending onfrom the season. First of all, the changes in the polar caps are striking. They grow and shrink, creating seasonal phenomena in the atmosphere and on the surface of Mars. The polar caps at their maximum expansion can reach latitudes of 50 °. The diameter of the permanent part of the northern polar cap is 1000 km. As the polar cap recedes in one of the hemispheres in spring, the details of the planet's surface begin to darken.
The North and South polar caps consist of twocomponents: seasonal - carbon dioxide and secular - water ice. According to data from the Mars Express satellite, the thickness of the caps can range from 1 m to 3.7 km. The Mars Odyssey probe discovered active geysers on the southern polar cap of Mars. According to NASA experts, jets of carbon dioxide with spring warming burst upward to great heights, taking with them dust and sand.
Data from the Mars Reconnaissance Orbitermade it possible to discover a significant layer of ice under rocky screes at the foot of the mountains. The glacier, hundreds of meters thick, covers an area of thousands of square kilometers, and its further study can provide information about the history of the Martian climate.
In 2018, the MARSIS radar installed on the Mars Express probe showed the presence of a subglacial lake on Mars, located at a depth of 1.5 km under the ice of the South Polar Cap (onPlanum australe), about 20 km wide.
How did the ice ages happen on the planet?
Scientists also learned about this after studyingpictures of the polar caps. Photos indicate that about 375 thousand years ago the ice age ended on the red planet, from which the planet is gradually emerging today.
The climate on Mars is changing much more than onEarth, since its axis of rotation «swings» noticeably more than that of our planet. Therefore, in the past, Mars could have looked completely different from how we see it today.
Isaac Smith, a researcher at the Southeast Research Institute in Boulder (USA).
By analyzing data collected by probe toolsMRO, when studying water ice deposits at the red planet's north pole, Smith and colleagues found that Mars had an ice age in the relatively recent past, after which it gradually warmed.
In the course of the new work, planetary scientists under the leadershipJoseph Levy, Associate Professor at Colgate University (USA), brought a little clarity to this issue. In the images of the Mars Reconnaissance Orbiter (MRO), they made out the first unambiguous traces of the fact that after the disappearance of most of the atmosphere, the planet's surface experienced several periods of glaciation.
Scientists were interested in landforms that couldform on the surface of Mars due to the movement of ice masses. One of the most noticeable structures of this kind is the so-called lobate sediment margins. This is what planetary scientists call accumulations of cobblestones and other rock fragments on the lower slopes of mountains and hills, which presumably got there as a result of the movement of glaciers.
When was the last ice age on Mars?
After analyzing hundreds of radar images from MRO andphotographs taken by probes from the Viking series more than 35 years ago, the authors of the article came to the conclusion that Mars was in an ice age relatively recently, about 370-375 thousand years ago.
During the retreat of glaciers at the poles of Mars,according to the calculations of planetary scientists, over 87 thousand cubic kilometers of water ice have accumulated, this would be enough to cover the entire surface of the red planet with a layer of water 60 centimeters thick. Such water reserves came as a surprise to scientists, who expected to see three times less ice than the data from the MRO instruments show.
According to the authors of the article, melting icecontinues today. This is evidenced by recently discovered traces of water movement on the surface of the red planet. Further observations of glaciers, the planetary scientist hopes, will help to understand what Mars will look like in the near future and how these changes will affect its potential habitability.
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