Exploring the Dust Storms on Mars
by: Najam Naqvi, Amanda Stehwien, Gillian Wankel
Introduction
The world population continues to proliferate with the projection to reach 9.7 billion by 2050 and 11.2 billion in 2100, according to the United Nations DESA report.1 Scientists are worried that our mother Earth is getting very crowded and our natural resources are being used up, making the land available to us smaller and smaller.2 This has caused some scientists and companies to consider colonizing outer space.3 Mars, being the closest and most similar to planet Earth, has raised a lot of excitement and is seen as one of the possible options for the expansion of humanity for decades.3 The climate of Mars has been a topic of astronomical curiosity for centuries as it is the only planet whose surface can be observed directly from Earth with the use of a telescope. Mars is known for its dust storms that occur all over the planet, some of which are big enough that they can be easily seen by orbiters around the planet, such as NASA’s Mars Reconnaissance Orbiter, and even telescopes on Earth.4 If humans were to colonize Mars, dust storms would be something that they would have to deal with, both small storms as well as global storms.
In this research project, we will be investigating the dust storms on Mars and answering the question, how will the dust storms affect colonization of the planet? To answer this question we will be looking at what a dust storm is and what causes them, the difference between a regular dust storm and a global one, the history and sequence of dust storms on Mars, how the storms have been studied by the rovers, landers, and orbiters on Mars, as well as looking at a couple of theories about what causes a dust storm to become a global dust storm. A lot is still unknown about the dust storms on Mars, especially how they become global dust storms, and they are still being researched and studied. They will have a big effect on colonization due to the amount of dust being stirred up by the storms, affecting solar power, machinery and technology, daily living, and travel, as well as causing other issues that cannot be predicted.
What are Dust Storms?
A dust storm is the movement of the dust on Mars which occurs due to wind velocity and a process called saltation.5 This creates a wind tunnel which brings the dust up into the air and then causes it to accelerate downward where it crashes into the ground causing new dust particles to launch into the air filling it will more dust each time.5 The lower gravity on Mars, due to its smaller size, and the higher wind velocities that are possible because of the lower gravity, contribute to the greater size and length of these dust storms in comparison to dust storms on Earth.5 The particles remain in the atmosphere longer, and they can go higher into the air once they are off the ground.5
While Earth’s atmosphere has not yet been significantly harmed by them, Mars’s atmosphere has been decreasing due to solar winds that have been occurring for billions of years and these solar winds are also believed to be the reason for the disappearance of water on the planet.6 Due to the lack of moisture on Mars, the atmosphere is filled with dust during different seasons which makes dust storms a common occurrence on the planet.7 These dust storms can be relatively minor and only cover a small area of the planet, but they can also occur on a global scale where they eventually grow to a size that covers the entire planet and last for several months, as seen in Figure 1.7
Figure 1. Global Dust Storm on Mars Credit: NASA/JPL https://photojournal.jpl.nasa.gov/catalog/pia03170
The atmosphere on Mars is much less dense than Earth’s atmosphere so faster wind speed is needed to blow things around when compared to Earth.8 That being said, the wind speeds in a typical dust storm get up to 97 kilometres per hour, which is less than half the wind speed of a hurricane on Earth.8 All of the dust that is constantly blown around, both in minor and global dust storms has significantly changed the surface of Mars, including changes in the brightness of some areas of the planet, the burying and exposing of rocks, as well as erosion.9
These differences in the climates and atmospheres of Earth compared to Mars would indeed make colonizing Mars quite dangerous to humans and their equipment. The constant dust that is blowing around on the planet and even more so during dust storms has proven to be disruptive to the landscape of the planet so when visualizing colonization humans would have to consider the possible ways to prevent the blowing dust and the dust storms from damaging equipment that they can freely use on Earth. Machines and technology would have to be designed or even redesigned to prevent this from happening.
Sequences and Historical Storms
Dust storms on Mars occur in an interannual pattern which makes it hard to predict which Martian year (equal to 687 Earth days) that they are going to occur in and which they are not.7 One thing that researchers have noticed throughout the years of monitoring Mars is that the global or near-global dust storms tend to occur during the summer or spring of a Martian year if they are going to happen.10 During the southern hemisphere’s summer and spring of a Martian year, the planet is closest to the Sun and there is a lot of heat in the atmosphere that heats the dust particles in the air and leads to the major dust storms.10
One of the most significant recorded dust storms on Mars was the storm in November 1971 when the Mariner 9 Spacecraft, seen in Figure 2, was sent to Mars to observe the planet.11 The Mariner 9 was the first spacecraft to orbit around another planet, and when it got to Mars, a massive dust storm was occurring which eventually covered the entire planet.12 The storm was so intense that Mariner 9 reported that the clouds of dust reached as high as 70 kilometres above the planet’s surface.11 The speed of the storm reached over 500 kilometres per hour which made the immense height of the storm possible.11
Figure 2. Mariner 9 Credit: NASA/JPL-Caltech https://www.jpl.nasa.gov/m/missions/detail.php?id=5905#.W9I1ofZFzIU
National Geographic Video about Mars Dust Storms:
The Mariner 9 spacecraft gathered an abundance of information about the atmosphere on its mission that has helped researchers calculate the atmospheric changes that occur during a dust storm as opposed to when it has cleared. In this mission and previous missions to Mars they made a common observation that during the southern hemisphere’s spring and summer the planet’s atmosphere is at its peak dustiness which could explain why the global dust storms only occur during this time.13 Scientists are continuing to study the sequences of the global storms and looking for the conditions that signal an oncoming dust storm which would help prepare a human colony to protect themselves and their buildings, as well as their technology and machines that would be harmed by the excessive wind and dust in the dust storms.
How The Storms Have Been Studied
Mars has been studied since the invention of the telescope, and, since 1960, with the failed launch of Marsnik 1 by the USSR, over 40 missions with orbiters, landers and rovers have been sent to the planet to learn more about it.14 Mariner 9 was followed by many other missions to learn about the planet, including the Mars Global Surveyor, Mars Odyssey, the Mars Reconnaissance Orbiter, and the Curiosity rover.
From 1997 to 2006 the Mars Global Surveyor, seen in Figure 3, orbited Mars and analyzed the planet with its various instruments.15 Using its Mars Orbital Camera, it took daily pictures that determined Mars has repeatable weather patterns.15 The images also revealed that the planet has smaller dust storms that repeatedly appear in the same locations and dust devils that typically show up once spring has started and continue until the fall.15 The Mars Global Surveyor also had a Thermal Emission Spectrometer that measured daily temperatures and how much dust was in the atmosphere.16
Figure 3. Mars Global Surveyor Credit: NASA/JPL https://www.jpl.nasa.gov/news/news.php?feature=6226
Many of the other missions sent to Mars have analyzed the planet using pictures, thermal infrared and gamma-ray instruments. Thermal infrared instruments are used to measure the chemical composition of the surface and atmosphere, and gamma-ray instruments measure the distribution of elements and how much of an element is present, also leading to the possible detection of ice and water.14 They have provided information on the dust storms from above the planet as well as from the surface. However, global dust storms are not too frequent, so there have only been a few opportunities to study them.
The most recent global dust storm started in June 2018 and there were several missions on the planet, as well as orbiting it, that studied the storm.17 Mars Odyssey used its Thermal Emission Imaging System twice a week to track surface and atmospheric temperatures and the amount of dust in the atmosphere as the storm grew and dissipated.17 The Mars Reconnaissance Orbiter used its Mars Color Imager to track the storm as it evolved and its Mars Climate Sounder to measure temperature changes in the atmosphere to see what effect the storm had on atmosphere temperature and how that compares to a year without storms.17 Curiosity, seen in Figure 4, is a rover that studies Mars from the surface and does not rely on solar power.17 It uses its instruments, including an ultraviolet sensor, to determine how much dust is in the air, as well as the size of the particles.17
Figure 4. Curiosity Rover Credit: NASA/JPL https://www.jpl.nasa.gov/spaceimages/details.php?id=pia19808
The dust storms of Mars have been studied for many years, but they are still not fully understood. However, as more is being learned about them more is known about their possible effects on a human colony. One thing that has been learned from the landers and rovers on Mars is that the dust stirred up in the storms collects on everything, including the solar panels, and needs to be constantly cleaned off for maximum solar efficiency. During the latest global dust storm the solar panels of the rover Opportunity were covered by dust too long and it is no longer responding to signals, most likely due to a fault from the lack of solar power.18 If a similar situation were to happen to a human colony it could potentially be a fatal problem so keeping solar panels clean would be essential, as well as having backup power supplies.
How And Why The Global Dust Storms Happen
Although scientists have been studying the dust storms on Mars for many years, they are still not exactly sure why some of the local storms become global, and others do not. One of the theories that scientists are currently investigating is that the smaller storms kick up dust into the air which then absorbs the sunlight and makes the surrounding area warmer.16 The warm air then moves towards colder areas, generating winds, which in turn lifts more dust into the air creating more warm areas, essentially creating a positive feedback loop, turning a small storm into a global one.16
Another relatively new theory for the formation of the global dust storms looks at the changes in the orbital angular momentum of Mars and how it may be a factor in the dust storms becoming global. Some scientists are starting to look at a possible relationship to the faster orbital angular momentum, leading to an increase in the surface winds on Mars, possibly being a factor in storms becoming global.19 They note that observations of the Mars atmosphere suggest that an increase of the circulatory flows leads to an increase in surface winds which could be necessary for the dust storms to become global.19 If this is true, then their hypothesis is that the changes in the orbital angular momentum of Mars could be a factor in creating those increased circulatory flows in the atmosphere.19 This theory is only in the preliminary stages and further papers will look at it in more detail.
Scientists are also unsure why there are so many years in between the global dust storms. It has been speculated that there is a cycle that the dust has to go through to be replenished and redistributed for the next global storm to be triggered, but scientists are still looking for the reason.8
Mars Before and After a Global Dust Storm:
Studying the storms of Mars will help scientists determine what causes them, allowing those who colonize the planet to have a better ability to predict the dust storms, which is especially important for the global ones. The global dust storms will cause the biggest issues for a human colony because of their duration and the amount of dust in the air. The duration of these storms will limit the ability of humans to see outside and likely cause navigation issues for rovers too, limiting the amount of time colonists could spend outside and put many experiments and testing requiring time outside on hold.22
Colonization of Mars
Colonization of Mars might not be possible as of now with the technology we have due to multiple factors; dust storms being one of the main ones. If humans were to colonize Mars, we would need advancements in technology that could prevent some of the effects of dust storms, such as machines to clear out the sand particles from the air for breathable air and to prevent the dust from getting into the lungs, potentially causing a health issue.20 Another adaptation would have to be designing machines so the fine dust cannot get into them and potentially cause them to stop working. Machines would need battery backups or different forms of power other than solar power because of all the dust that collects on them over time, especially during a dust storm.20 There would also need to be better technology and health care to cure diseases that Mars and travel to the planet could potentially cause.21
The global dust storms, such as the one observed by Mariner 9, where the dust clouds reached 70 kilometres above the planet’s surface and wind speeds of 500 kilometres per hour, would be a big obstacle for a colony to overcome. As mentioned previously, the visibility would be quite reduced, as shown by the pictures and measurements taken by Curiosity in the most recent global dust storm, which would affect the ability of colonists to see outside and cause navigation problems for rovers.23 The biggest obstacle to overcome, however, is learning more about these global dust storms and how they occur so they can be predicted and help colonists minimize the risks to themselves and their colony, as well as all of the technology and machines necessary for survival.
Mars One, one of the companies currently investigating a colony on Mars, has looked at dust storms as something the colonists will have to deal with. They have created guidelines to help them plan and train for the storms. These guidelines include shutting down or restricting the non-critical systems in order to save power during a storm, storing dirty water for recycling once power is available again, dimming greenhouse lighting, limiting human and rover activity outside the habitat except for emergencies, and using oxygen and water from storage tanks only. 22
Click here to view several panoramas of Mars taken by the Curiosity Rover http://www.360cities.net/sets/curiosity-mars
Conclusion
In this research paper, we looked at the dust storms on Mars and answered how they would affect potential colonization of the planet. They will affect colonization of the planet by causing many issues due to the dust and unpredictability of the storms. Scientists continue to study the storms from orbit and the planet’s surface using rovers, landers and orbiters, to find out what causes a smaller dust storm to turn into a global storm, but the mechanism for how that happens is still not understood. The most recent global dust storm began in June 2018 and scientists continue to study the information they gathered during the storm. Small, local dust storms occur often on Mars, especially during the warmer seasons, but global dust storms are much more infrequent, occurring several years apart. The dust storms would affect a potential colonization in several areas, including the necessity of building machines where dust is unable to get in, filtering dust out of the air that the colonists breathe, limiting travel and outdoor activities, and needing alternative power sources for essential systems during a storm.
Colonization of Mars seems like the next logical step for our space exploration as Earth would get more resources for humanity after some centuries as the population rises. Mars is much more habitable for humans compared to all other planets in our solar system. Although, there are some challenging obstacles our scientists have to overcome regarding technological advancement to sustain human life on Mars.
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