When you imagine the challenges of putting humans on Mars, you likely think of the big issues: Designing a rocket to carry astronauts through the solar system, building a habitat to keep them safe, and making sure they have water to drink and food to eat.
These are certainly significant challenges. But the most serious problem for human exploration of Mars may in fact come in the form of something tiny: Dust. Mars is one of the dustiest places in our solar system, subject to epic dust storms that cover the entire planet and can last for weeks at a time. And this dust can cause problems in everything from astronaut health to landing a vehicle on the planet’s surface to the operation of life support systems.
To learn more about the big problems caused by these tiny particles, we spoke to two experts on Martian weather and human exploration of Mars.
If it seems odd that something as small as dust could be a major challenge in space exploration, consider the many different ways this apparently minor inconvenience has affected missions in the past. Moondust turned out to be a major issue on the Apollo missions, as lunar dust is extremely sharp and abrasive. It stuck to everything due to static electricity and was so corrosive that it ate through spacesuits and containers.
“That dust played havoc with the astronauts and with their equipment and their systems,” Joel S. Levine, research professor in applied science at the College of William and Mary who co-chaired NASA’s Human Exploration of Mars Science Analysis Group, told Digital Trends. Even when the astronauts tried to brush the dust off, they still carried it back into the lunar module and then to the command module. “There was so much lunar dust in the command module that it actually affected several of the systems,” he said. “The dust clogged things up.”
The problem is that dust particles are so small that they can get into everything – any tiny hole, crack, or joint. Because there is no atmosphere on the moon, there is no erosion, so each particle is like a tiny shard of glass. And the dust can wear away or even break components like bearings or seals.
The dust affected the astronauts themselves too, causing respiratory irritations and eye irritations. It caused such problems that in their debriefings, many of the Apollo astronauts named dust as a significant obstacle for future moon missions. NASA now considers lunar dust to be a major issue for the upcoming Artemis mission to the moon.
The dust on Mars is different from that on the moon. Martian dust isn’t sharp like lunar dust — instead, it’s dangerous to humans in a different way.
The first concern is about how small the particles of Martian dust are. “The smaller it is, the more damage it can do,” Levine explained. Tiny particles can get into spacesuits, helmets, or habitats and be inhaled by astronauts, causing medical issues similar to the black lung disease commonly suffered by miners who have inhaled coal dust.
The second concern is whether Martian dust is toxic to humans. We know that the Martian soil contains chemicals called perchlorates, which are found in small quantities here on Earth and which are known to be carcinogenic, causing thyroid problems and lung problems. There are also traces of toxic gas metals in the atmosphere too, as well as reactive gases like hydrogen peroxide and ozone.
This means that the surface of Mars is very chemically active, and currently, we just don’t have enough data to know how dangerous this could be for visitors.
“We don’t really know the composition of dust in the atmosphere of Mars,” Levine said. “But perchlorates and trace gas metals, chromium, for example, can be toxic. On Earth, they are very trace, and we don’t know what the concentration is in the crust of atmosphere of Mars.”
And unlike lunar missions, where astronauts were spending a few hours at a time on the surface, astronauts on a Mars mission will spend weeks or months being exposed to this environment.
That’s why agencies like NASA are preparing to protect astronauts from this risk by designing a next generation of spacesuits with advanced dust control to keep these dangerous particles away from the explorers. But to do this, they need to know more about the potential dangers they are protecting the astronauts against. And for that, we’ll need to bring a sample of Martian dust back to Earth for study.
The threat to astronauts is only one part of the dust issue though, as Jose Antonio Rodriguez-Manfredi, doctor of engineering at Spain’s Center for Astrobiology (Centro de Astrobiología), explained to Digital Trends.
Understanding the way that dust impacts the atmosphere will be especially critical for the landing of future human missions to Mars. That’s because the amount of dust in the atmosphere varies throughout the year and by location, and it can dramatically affect the temperature and density of air on the planet, and that affects how parachutes and aerobrakes work.
“Even if the knowledge about dust was enough for the design of the current missions, like Perseverance, this is not enough for the future.”
We do know how to land rovers on the surface of Mars — although the process is certainly not an easy one. However, current landing systems won’t be sensitive enough for landing people. That’s because current landing systems like those used for NASA’s Curiosity or Perseverance rover missions are designed to have a significant margin of flexibility. The engines used in the Entry, Descent, and Landing system are specifically designed to be larger and more powerful than necessary on average so they can cope with variations in temperature and air density.
But this over-dimensioning has a cost, in terms of weight and fuel. And even more importantly, there is more of an acceptable degree of risk with a rover than with a human life. “If something happened to Curiosity or Perseverance, this is an amount of money,” Rodriguez-Manfredi said. “An important amount of money, but it is just money. In the future, on human missions, the risk is not just to money but to life.” So there’s an imperative to reduce risk as much as possible. And to do that, understanding dust is essential.
“Even if the knowledge about dust was enough for the design of the current missions, like Perseverance, this is not enough for the future,” Rodriguez-Manfredi said.
Dust affects how technology operates once it’s on the surface as well. When it comes to the Perseverance rover, currently on its way to the red planet and scheduled to land there in February 2021, it will carry experiments to see if we can produce the materials we need to sustain life on the planet.
One such experiment is MOXIE, or the Mars Oxygen In-Situ Resource Utilization Experiment, which is a small demo version of an oxygen machine. MOXIE takes in carbon dioxide, which is abundant in the Martian atmosphere, and it produces oxygen. The idea is to test whether this technology works as well in practice as it does in theory and, if it does, to build a giant version in the future which could provide astronauts with the oxygen they need for breathing and for fuel.
The problem is that as MOXIE sucks up carbon dioxide from the atmosphere, it’ll be sucking up dust as well. Engineers can install filters to keep out as much of the dust as possible, but to be most effective, they need to know what type of dust they’ll be filtering.
“Dust is critical for the mission,” said Rodriguez-Manfredi. “MOXIE’s performance will eventually depend on how the filters it has on the inlets may be blocked by the dust. Knowing the dust size, the dust abundance, even whether it is spherical or tubular or another shape, will affect the performance of that filter.”
When it comes to the machine that will enable astronauts to breathe, there’s no room for error. The safety of any human crew has to be the top priority, and that means doing everything we can to understand what could go wrong with essential technology.
To understand how to beat dust, we have to understand where it comes from. And to understand that, we need to know all about the Martian weather.
Like Earth, Mars has winds, storms, and regional and seasonal variations in weather. But unlike Earth, Mars has an extremely thin atmosphere (around 1% the density of Earth’s atmosphere) and a smaller size and lower gravity (around 40% of Earth’s gravity). Mars also doesn’t have plate tectonics, and its inside is thought to be inactive. All of these factors affect the Martian weather.
The lower gravity means that gases in the atmosphere are more easily lost into space, so over time, Mars is losing its atmosphere. And the atmosphere that it does have is 95% carbon dioxide, which acts as a greenhouse gas. This means that the atmosphere is moving around a lot, due to variations in temperature and pressure — and that means that tiny particles of dust are whipped around all over the planet.
This leads to huge wind storms, with winds traveling at up to 90 mph, which lift dust into the atmosphere. This can happen across all of Mars at one time, wrapping the entire planet in an epic global dust storm.
When you picture a Martian dust storm, you might think of huge gusts of wind blowing equipment over and dragging antennas across the surface of the planet, like the dust storm portrayed in the opening of the movie The Martian. But that’s not quite right, Rodriguez-Manfredi said.
There are huge gusts of wind, but they wouldn’t be knocking equipment over and dragging it around. “Even if we have huge winds, we will never have those problems with dragging conditions, because of the density,” he explained. The thin atmosphere means that, if you were on the planet in such high winds it would feel only like a light breeze.
But even that light breeze is enough to pick up the dust particles, because they are so small, and to whip them into a global dust storm that covers everything in a blanket of dust. This phenomenon is highly unusual, and we’re just starting to understand the mechanisms through which it operates. “We don’t know how, on a planet like Mars, the winds we have there are able to lift all the dust at the same time,” he said.
To understand how these global dust storms form, we need more data.
To that end, Perseverance is carrying an instrument called MEDA, or the Mars Environmental Dynamics Analyzer. Rodriguez-Manfredi is the principal investigator for MEDA, which will gather data on the Martian weather. It will collect data on essential weather readings like temperature, wind speed and direction, pressure, and humidity. And, even more importantly, together with other sensors on the planet like those on the Curiosity rover and the Insight lander it will form a network of weather stations that will help us to understand the planet’s meteorological system.
This will help in the massive challenge which is forecasting the weather. Weather systems are complex and chaotic, where a small variation in one factor in one region can have big effects on the weather in another region days later. Data from these points on the surface can be combined with readings taken from orbit to build up an overall picture of what to expect from the Martian weather.
There’s another key function of MEDA though, and that is to study the dust itself. On MEDA, there are many different sensors that will help to provide information about these dust particles. “So in addition to the general environmental magnitude, MEDA will focus on the characterization of the dust,” Rodriguez-Manfredi said.
With data on the amount of dust in the air at different times of day, as well as data about the dust particles’ shape and size, future engineers can build systems that are more resilient to the relentless barrage of dust they will face.
The threat of dust in Mars exploration isn’t about a dramatic dust storm blowing things away, it’s about tiny particles gradually infiltrating spacesuits and habitats and causing long-term damage to astronauts and equipment.
To win the war against these tiny invaders, we need data: Data about the dust particles, and about how they are affected by the complex Martian weather system. It’s this knowledge that will protect future explorers when they eventually travel beyond Earth and set foot on another planet for the first time.
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