Global dust storms may become predictable, which will naturally make life easier for future Martian explorers. A new study has been able to build a model indicating that the Red Planet will experience a similar event in the next few months. She also indicates that its start is expected on October 29th or several weeks from the designated date.
Local dust storms are a very common occurrence on Mars. They sometimes grow, merge and form a regional one, especially during the southern spring and summer, when the planet is closest to the Sun. Quite often, regional storms cause the formation of a dust fog that encircles the planet and makes it impossible to see the surface from above.
But sometimes, regional ones transform into global ones; one of them, in 1971, was observed by the first spacecraft launched into Mars orbit, Mariner-9, as well as the Soviet stations Mars-2 and -3. Creating a kind of template by which the onset of global storms can be determined over several years is still considered an unsolved problem.
The last storm on a planetary scale occurred in 2007. It was then that the flow of sunlight to the surface significantly decreased, which led to problems in the operation of two all-terrain vehicles - Spirit and Opportunity. In fact, this event was the first significant threat to the all-terrain vehicles since landing.
It was necessary to take special measures to ensure their survival for several weeks, in conditions with little sunlight. Both rovers worked for only a few minutes each day, and then only to provide heating for the on-board equipment, and then turned off and did not communicate with the Earth at all during the next day.
Dust storms will create serious problems for the first colonists of the Red Planet. Although the winds there are not as strong as depicted in the movie The Martian, dust from storms will definitely affect electronics as well as the availability of sunlight.
Since 1924, 9 global dust storms have been recorded on the Red Planet, of which the last five were discovered in the period 1977-2007. It is clear that their number is undoubtedly greater. The fact is that at some periods of time there were no research vehicles in the orbit of Mars to observe such a phenomenon at close range. It is extremely difficult to see them from Earth.
The study found a pattern in the occurrence of storms when the orbital motion of Mars is accurately taken into account. It has been discovered that sometimes other celestial bodies influence its rotation around the Sun. If the impact increases, global storms typically occur during the first part of the storm season. None of them occurred in years when influence was declining.
Current conditions on Mars are very similar to those when global storms have occurred in the past. Observations of the atmosphere in the coming months will test whether the forecast is correct.
During the exploration of Mars by the Soviet automatic stations Mars-2, Mars-3 and the American station Mariner-9, a severe dust storm erupted on the planet. It started in September 1971.
On that day, Earth's observatories discovered a white cloud strip approximately 2,400 kilometers long and 400 kilometers wide. Then the stripe turned yellow and began to quickly, at a speed of about 100 kilometers per day, spread westward across the planet, covering it with a yellow haze. After 16 days, a thick shroud enveloped the entire western hemisphere of Mars. By the end of October, nothing could be discerned on the planet. The atmosphere began to clear only in mid-December 1971.
Why do such strong dust storms occur on Mars?
The first to notice the clouding of certain areas of Mars was the French astronomer O. Flogerguet in 1796-1809. About one hundred and fifty years ago, scientists first suggested that the yellow clouds on the planet were composed of dust particles. It was later determined that these clouds appear where the surface of Mars heats up more than usual.
Yellow clouds almost every time cover the entire planet at a time when it is near perihelion - the point of its orbit closest to the Sun. At this time, summer is just beginning in the southern hemisphere of Mars, where global storms occur. The connection between the heating of the planet and the appearance of an all-Martian dust blanket has been noted more than once by astronomers. They noticed her over the years. These are the years of Mars' great oppositions, when it comes closest to Earth and when we can best see it.
Further research has shown that the rise of small amounts of dust into the Martian atmosphere almost always occurs during the warm season during the Martian noon and afternoon hours. This was confirmed by an analysis of tens of thousands of photographs taken under the International Planetary Patrol program.
So, large dust storms on Mars appear when the planet's surface overheats. Another necessary condition is a wind of sufficiently high speed: about 50 meters per second. Vertical movements in the atmosphere and the degree of surface roughness are also important.
The beginning of a storm can be imagined like this. Particles of about 200 microns in size rise first. The wind cannot yet lift the heavier ones from the surface, and the lighter ones do not take off due to the vortices. The wind speed increases - large and small particles rise. The large ones immediately fall to the surface and knock the smaller ones up. They, in turn, rise to great heights. The flow can weigh particles and hold them in itself. Particle size is one or several microns.
Finally, the dust cloud reached a large size; the concentration of dust in it was very high. A new stage begins: the cloud influences the flow that gave birth and carries it. Flying particles streamline the movement of the wind, making it more stable and therefore faster. This paradoxical fact was established by Soviet scientists when studying dust storms in Kazakhstan. Earthly dust storms sometimes reach simply frantic force - wind speeds often exceed 40 meters per second.
On Mars, temperature differences near the surface of the planet can reach 100 degrees Celsius. Temperature can also change dramatically with altitude - within just a few meters. This creates instability in the atmosphere and contributes to an increase in wind speed with height. It is clear why dust storms occur in the warm season - heating the surface makes the Martian atmosphere more unstable.
And finally, one more circumstance. When a planet is covered by a dust cloud, much of the solar radiation is absorbed by the dust in the planet's atmosphere. Therefore, the atmosphere becomes warmer, and the surface of the planet becomes colder than usual. Because of this, strong whirlwinds can occur under dust clouds. They become new suppliers of dust to the cloud. This will only stop when the cloud becomes large enough and reduces temperature contrasts in the atmosphere. Dust particles will begin to fall out.
What about our planet? Dust storms on Earth are among the most dangerous natural phenomena. To fight them, you need to know everything about them. This is why the study of dust storms in planetary science is so interesting and important.
It is known that dust storms are raging on Mars; these storms can be incredibly large and can cover the entire planet. In addition, the surface of Mars is dotted with countless tornadoes, rushing across its plains and kicking up dust, carried away in a “dust cycle” unique to the planet.
Images taken from orbit show winds are the main cause of erosion on Mars. Vast dune plains, intricate rock formations and hazy skies - such is this harsh, windy world.
Science fiction writers quickly picked up the idea of frequent storms that look terrifying from afar. Gigantic walls of dust, against which the greatest terrestrial dust or sand storms look ridiculous dwarfs, sparkling spears of lightning that arose due to atmospheric friction, monstrous hurricanes that sweep away everything in their path, scattering astronauts and twisting equipment.
Alas, the realities of Martian dust storms are somewhat more modest - a fact that NASA wants to convey to audiences eagerly awaiting Ridley Scott's new film The Martian.
Based on the best-selling book by Andy Weir, the film takes place in the near future during a manned mission to Mars. Due to a ferocious dust storm, the mission fails, the planetary base is damaged, and one of the astronauts, Mark Watney (played by Matt Damon), is lost after his spacesuit is damaged and colleagues believe that he died in the terrible Martian winds.
But, like many other science fiction speculations on the topic of Mars, this scene misleads the viewer, since scientists have slightly different data on its atmospheric pressure.
Although, of course, dust storms on Mars are dangerous in their own way, it is extremely unlikely that they will throw anyone around or damage anything. The strongest Martian winds blow at 60 miles per hour (less than 30 meters per second), half the speed of any Earth hurricane. In fact, however, the damage is caused not so much by the wind speed itself, but by atmospheric pressure, which is a little tight on Mars. It is approximately one percent of the Earth's, so if you decide to go kiting on the Red Planet, you will be quite disappointed.
"The main difference between the atmospheres of Earth and Mars is that the pressure on the latter is much lower," says physicist William Farrell of the Goddard Space Flight Center in Greenbelt, Maryland, who analyzes Martian dust storms. “So, of course, the winds blow, but not that much.”
Although the most violent hurricane on Mars would be more like a breeze by Earth's standards, Martian dust storms could still pose a problem for future astronauts, especially if they depend on solar energy.
In The Martian, Watney cleans the solar panels every day to keep them free of dust. As the experience of solar-powered rovers on Mars, in particular NASA veteran Opportunity, which has been traveling on Mars on solar power for ten years, has shown, this is a serious problem that seriously affects the amount of energy received. When the atmosphere becomes saturated with fine dust during storms, little sunlight reaches the surface.
"We're concerned about power supply for Mars rovers, it's an important issue," says scientist Michael Smith, also of the Goddard Center. “Spirit and Opportunity were delivered to the planet in 2004 and have only encountered one serious dust storm so far (in 2007), but then they had to essentially stop functioning and go on life support for several weeks.”
But fine dust isn't just a nuisance when it comes to solar panels. Not only are its particles magnetized, they are also covered with sharp jagged edges (since there are no other erosion processes on Mars to break them in), capable of causing mechanical damage.
"If you've seen pictures of Curiosity after its trip, it looks like it was dug out of a hole," Smith added. “Dust covers everything like a blanket and gets into every moving joint.”
The dusty atmosphere of Mars will undoubtedly cause problems for ground vehicles, as well as the health of astronauts, if we ever send a long-term expedition there (in addition to increased levels of radiation and toxic substances in the Martian regolith and soil). In addition, the causes of planetary dust storms are still poorly understood.
“Relatively large dust storms occur on Mars every year, they are continental in size and last several weeks each,” says Smith. “But every three Martian years (about five and a half Earth years), a normal storm grows to planetary proportions, what we call a ‘global dust storm’.”
“Perhaps the storm needs time to gather its strength. Maybe there is some kind of cycle that she needs to go through and then get to the right place and launch a new storm, or maybe it’s just a matter of chance.”
Humanity has observed global dust storms on Mars since 1909, the last one happened in 2007, so Mars is just waiting for a new giant.
"We're waiting for a global storm, and this time it's going to be really big, so it's going to be fun," he says. “I love dust storms.”
With each successive storm on Mars, we learn more and more about the processes occurring there in order to better prepare for the first landing on this dusty, unfamiliar planet. But as for fierce storms, you can be sure that no one except the Martian Watney will be blown away by its winds.
NASA has revealed truth and fiction about the dangers of dust storms on Mars, some of which may be visible from ground-based telescopes. This information was used in the creation of the new film "The Martian" directed by Ridley Scott. This was reported on the NASA website.
Dust tail (Photo: NASA / JPL-Caltech / University of Arizona)
The Martian, which will be released in October 2015, begins with Andy Weir's character (astronaut Mark Whitney) facing a massive dust storm. She tears down the transmitting antenna and destroys part of the camp. NASA does not deny that dust storms are one of the unpleasant features of the Red Planet.
"Every year, Mars experiences moderate-to-large dust storms that span areas the size of Earth's continents and last for weeks," said planetary scientist Michael Smith of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Meanwhile, on the Red Planet, as the scientist noted, much stronger storms are observed. Global dust storms are formed from moderately large ones and manifest themselves on average once every three Martian years (this corresponds to approximately 5.5 Earth years).
However, as the scientist notes, it is unlikely that these dust storms will even disturb the hair of an astronaut on the Red Planet (if the latter decides to take off his spacesuit). In addition, even global dust storms are likely to be unable to knock over or destroy any equipment.
This is because the strongest winds on Mars are no faster than 27 meters per second, which is more than half the speed of some hurricane-force winds on Earth. In addition, the density of the Martian atmosphere is one hundred times less than that of the Earth.
Dust from a storm in 2008 covered Spirit's panels (Photo: NASA/JPL-Caltech/Cornell)
“The main difference between Earth and Mars is that the atmospheric pressure on the Red Planet is much lower,” said plasma physicist William Farrell. “So everything [particles in the atmosphere of Mars] becomes wind, but not with the same intensity [compared to Earth],” he added.
However, dust storms on Mars are not completely harmless. Individual small dust particles can carry an electrostatic charge and “stick” to surfaces, particularly windows and mechanical parts of scientific equipment.
Neutralizing electrostatic charges and eliminating dust contamination is one of the main tasks that engineers designing equipment for Mars exploration solve.
This same dust is a big problem for solar panels. Even small dust storms can deposit enough particles onto solar panels to significantly reduce solar energy output.
In the movie The Martian, astronaut Whitney cleans up dust pollution from solar panels every day. NASA also notes that global storms on Mars could also lead to some darkening of the Red Planet's atmosphere.
“We were really worried about the energy of the rovers. The Spirit and Opportunity rovers, which landed on Mars in 2004, only experienced a global storm once (in 2007) and basically stopped working for a few weeks and went into survival mode,” Smith said.
Most often, global dust storms on Mars occur in the summer in the southern hemisphere of the planet. Like on Earth, the seasons on the Red Planet are determined by its inclination to the plane of its orbit. However, Mars' orbit is more elongated than Earth's, meaning that during the Martian year, one side of the planet is hotter than the other.
For more than a hundred years, science fiction writers from around the world have been trying to imagine what life would be like for astronauts on Mars. But, as humanity becomes increasingly more and more aware of Martian conditions, science fiction writers' descriptions of life on Mars are becoming increasingly more realistic. More recently, the film “The Martian,” which is based on the science fiction novel by Andy Weir. The main character of “The Martian”, due to unforeseen circumstances, is left alone on the red planet and begins the struggle for survival. And at the beginning of the 20th century, the American author Edgar Rice Burroughs was already dreaming of traveling to Mars. To be fair, it should be said that the red planet fascinated people so much that even the famous theologian and author of fantasy stories, Clive Staples Lewis, published a series of stories about it. It was he who created the “Chronicles of Narnia” cycle.
An artist's impression of a dust storm on Mars bearing down on a research station. Such phenomena on the red planet may well be accompanied by discharges of atmospheric electricity. Source: NASA
The Martian opens with a huge sandstorm that damages a transmission antenna and some equipment, leaving the fictional character Mark Watney stranded on Mars while the other mission members fly away, presumed dead. This development seems very plausible, since Mars is famous for its very active sandstorms, which sometimes become so large that they can be observed in telescopes on Earth.
“Every year, moderately large sandstorms occur on Mars, covering areas the size of Earth's continents and lasting for weeks after they form. But about every three Martian years (5.5 Earth years), ordinary hurricanes turn into giant storms that can envelop the entire planet,” Michael Smith, a planetary scientist at NASA Space Flight Center.
Scientists consider it unlikely that even planetary sandstorms on Mars will be able to lead to severe consequences. Even the strongest winds that blow at this time will not be able to destroy or even overturn specially deployed mechanical equipment. The winds in the strongest Martian hurricanes reach speeds of about one hundred kilometers per hour, more than half the speed of some hurricanes on Earth. That is why you should not focus only on wind speed. Atmospheric density Mars is approximately one percent plrelation to the atmosphere Earth. This means that in order to fly an Earth-like kite on the red planet, the wind would have to blow much stronger.
“The main difference between Earth and Mars is that the atmospheric pressure on Mars is much lower. Thus, things and objects can be carried away from its surface, but not with the same force as on Earth,” William Farrell, plasma physicist.
Problems of solar energy
But be that as it may, sandstorms on Mars are not completely harmless. Individual dust particles on the red planet are very small and slightly electrostatic, so they are able to “stick” to various surfaces.
“If you've ever noticed, you'll notice in pictures of the Curiosity rover that it gets very dirty after every trip. Dust covers almost everything. It even penetrates into mechanisms and devices,” Michael Smith.
This ability for dust to get everywhere is a major challenge for engineers designing equipment for Mars rovers. This is especially a big problem for solar panels. Even if the craft were caught in a very small dust storm or vortex, just a few meters in size, the wind could carry enough dust to cover the photovoltaic converters and significantly reduce the usable surface area capable of converting solar energy into electricity. If we go back to The Martian, Mark Watney spends a certain amount of time every day cleaning the solar panels to ensure their maximum performance.
The Opportunity rover took this image of itself three weeks before its tenth anniversary on Mars. The Pancam panoramic camera filmed the rover from January 3 to January 6, 2014. Notice how dusty the solar panels are. Source: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
Global hurricanes can also create a secondary problem that cannot be solved by simply blowing dust from the surface. There may be such a constant amount of dust in the atmosphere that some part of the sunlight will be blocked, and, consequently, the efficiency of solar panels will decrease. In the book, when the astronaut first encounters a large sandstorm, he immediately notices a slight decrease in the efficiency of his batteries caused by the slight darkening of the atmosphere. This is a fairly accurate description of what researchers might encounter during actual Mars missions.
“We are currently very concerned about the energy consumption of our rovers. The Spirit and Opportunity rovers descended to the surface in 2004, so they have only survived one global hurricane so far in 2007, which forced them to stop operations and go into standby mode for several weeks,” continues Michael Smith.
dust bustle
As mentioned, global sandstorms kick up enough dust to completely cover the planet and block out the Sun. but this way the hurricane itself also becomes doomed to extinction. The fact is that the main mechanism that sets all these hurricanes in motion is the high temperature of sunlight, which reaches the surface of the planet. As light hits the ground, it warms the air close to the surface, leaving the upper layers cooler. Just like on Earth during thunderstorms, warm and cold air, mixing, become unstable, warm layers begin to rise, taking with them dust particles due to instability. It is from these small swirls that all those strange dust “ghosts” seen in some images of Mars are formed. Then moderate-sized storms form, then continent-sized storms. Sometimes such large hurricanes can unite into one global whirlwind, which covers the entire planet with dust.
Researchers and planetary scientists have determined quite accurately that large hurricanes typically occur during the summer in the southern hemisphere of Mars. It is known that on the red planet, just like on Earth, there is a change of seasons, which is caused by the tilt of the planet’s rotation axis. But due to the fact that Mars' orbit has a greater eccentricity than Earth's, the red planet moves in a more elliptical orbit. The minimum approach to the Sun coincides with the summer period in the southern hemisphere, and, therefore, the temperature values are the highest then. Once a hurricane begins, it does not subside for weeks or even months. But scientists are still unsure what exactly causes such long gaps between hurricanes.
A dust devil captured on Mars by the HiRISE camera of the Mars Reconnaissance Orbiter. This scene was captured during the daytime in late Martian spring. The frame covers an area measuring 644 meters. Judging by the shadow that the vortex casts on the surface, it was possible to establish that it can reach 800 meters in height, and its diameter is about 30 meters.
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