Mars has a very thin atmosphere and the lack of water vapor makes it feel much colder than Earth.
Scientists aren’t sure if we will ever discover life on Mars, but the planet does have its own climate and weather patterns. Let’s take a closer look at how it works.
Temperature
The average temperature on Mars is -81 degrees Fahrenheit (-60 C), and it can be a lot colder in the winter. It can also be very hot in the summer near the equator.
The temperature of Mars varies every Martian year, as it does on Earth. This is due to the fact that there are no oceans on Mars and the planet’s rotational axis has a slight inclination.
Temperatures vary from season to season, but not as much as they do on Earth because the atmosphere is thinner and there are less water vapor molecules in the air. That makes the temperature feel less cold than it actually is on Mars, according to Michael Mischna of NASA’s Jet Propulsion Laboratory.
In addition, the weather on Mars is often characterized by strong thermal tides, or rapid changes in atmospheric pressure. These are caused by heating of the surface by the sun. The atmosphere on Mars is significantly lower in pressure than the Earth’s atmosphere, so these tides are much more intense.
These tides are also related to the planet’s tilt of its axis, which is a factor in the formation of ice-rich features on Mars. Large tilts of more than 80 degrees have been observed.
This has led to the belief that ice-rich areas of Mars may be formed by frozen water, which was once on the planet’s surface. Scientists are still trying to understand why this happened.
It is also possible that the ice-rich areas of Mars were once covered with liquid water. However, there is little evidence to support this theory.
Another hypothesis is that water ice on the surface of Mars could have been frozen by a solar wind or other force. This would explain the existence of the Ismenius Lacus ice caps and other icy features on Mars.
In addition, some scientists believe that psychrophiles and cryophiles – extremophilic organisms that can survive very low temperatures – might be able to thrive on the Mars surface. But this is a very difficult question to answer because of the extreme variation in temperatures on the Red Planet.
Atmosphere
The Martian atmosphere is composed mostly of carbon dioxide, and contains other gases such as nitrogen and argon. Some of these gases are lost to space, while others are locked up in rocks on the surface. This atmospheric loss makes Mars’s atmosphere thinner than on Earth, and makes it less breathable.
Atmospheric concentrations of the five major gases — carbon dioxide, nitrogen, argon, oxygen, and water vapour — vary significantly between seasons. These changes help to explain the planet’s climate and may also point to past life on Mars.
Clouds are another component of the Martian atmosphere. There are four main types of clouds: cirrus, aphelion (or “northern hemisphere” clouds), lee waves behind tall volcanoes, and polar hoods.
Most clouds on Mars are formed from ice particles instead of water droplets, so they have much less impact on air movements than on Earth. But in polar winter, clouds of carbon dioxide can condense and form huge dust storms that can last weeks or longer.
Solar heating of the atmosphere on a daily basis, and large scale expansion from solar wind, drive the weather patterns on Mars. These are independent of gravity, which means they can be more complex and difficult to study.
These systems are strongest in the southern part of the planet, and weaker in the northern part. They are triggered by the large mountains rising out of much of the planet’s atmosphere and the planet-wide gradient (high southern pole to lower northern lowlands).
The high mountains and their slopes also act as ‘jet streams’, generating powerful winds flowing from the south through the upper atmospheric boundary layer to the south. This jet stream can be very strong, ejecting dust into the upper atmosphere at speeds over 100 km/s.
This can have a significant impact on Global Circulation Models, as it can cause air pressure to change from one side of the planet to the other and back again. It can also cause updrafts, which may lead to localized cloud formation, especially if the temperature is very cold.
The Martian climate has changed dramatically over the past few million years, as carbon dioxide and water vapour have been ejected into space. These processes have led to a thin, ‘puffier’ atmosphere, which can cool rapidly when it’s hot on the surface.
Wind
Mars is much thinner than Earth’s atmosphere, which means it doesn’t have a “thermal blanket” to hold back heat from the Sun. This means that it can get quite cold on the planet–the average temperature is about minus 80 degrees Fahrenheit (minus 60 degrees Celsius) at its equator and even further north, near the poles.
Despite its thin air, wind on Mars can still whip up dust storms. These are called dust devils, and they can cover entire Martian surfaces.
These winds are caused by differences in pressure and temperature between the surface and the atmosphere. This pressure disparity is one reason why dust devils occur on the planet, says University of California San Diego physicist and study co-author Thomas Wiens.
It’s also why the planet can get so cold, says University of Arizona astronomer and study co-author Scott Guzewich. Because of this difference in density, molecules on Mars don’t hold onto the same amount of heat as ours do, so they tend to move from high to low pressure, causing a large temperature gradient over the planet’s surface, he and his colleagues write in Nature Astronomy.
This contrast in temperature can lead to strong cyclonic winds that blow down crater rims and volcanic highlands. These are called slope winds and mimic thermally driven mountain and sea breezes on Earth.
However, these aren’t strong enough to make a turbine useful for powering human exploration on the planet. That’s why scientists have dismissed wind as a potential power source for missions to Mars in the past.
But that’s about to change, thanks to a new model that identifies regions with potential to generate wind energy. This can expand the range of landing sites and regions that scientists previously discredited because of a lack of solar power, Hartwick and her colleagues report in the journal Science.
The researchers used topographic, heat storage, and albedo maps from previous observations to simulate the wind patterns and strength on the planet’s surface. They found that the highest power potential peaked during each hemisphere’s winter, at night and dawn, and during dust storms that occluded sunlight. In addition, the wind speeds and patterns varied with time of day and season. This allowed the team to compare wind power levels with available solar energy. It also helped identify regions with the best potential to power human exploration, including many that were previously discredited on the basis of solar energy availability.
Ice Caps
The planet Mars has a number of ice caps that cover its north and south poles. These ice caps contain a thick layer of frozen carbon dioxide ice that forms each fall and winter, disappearing as the planet warms into summer.
But there is another layer of ice beneath the north polar cap that scientists believe is made up of water ice. This ice is thought to have formed a few hundred years ago or more.
In addition to the ice cap above, Mars also has a layer of dry ice that consists mostly of carbon dioxide. This layer freezes during the winter and partly sublimates in the spring when temperatures rise above -125deg C.
This dry ice is so thin it’s hard to see through with the naked eye, but researchers have managed to photograph it using the Mars Odyssey orbiter. These photos show dark dune spots and lighter fans atop the dry ice, indicating that solar heating causes geyser-like eruptions of CO2 gas beneath the ice in places.
These observations led to the idea that the polar ice caps contain layers of liquid water trapped under a layer of frozen carbon dioxide. But determining whether those polar ice caps are a real signal of Martian climate has been difficult, especially because the axial tilt and precession angle of Mars’s orbit affect the thickness of ice in those regions.
A team of scientists at the University of Cambridge in England has now found further evidence that this liquid water exists on Mars today. The team mapped the surface of the ice caps with laser-altimeter measurements from NASA’s Mars Global Surveyor satellite and matched those maps to computer models that predict how a layer of subglacial liquid water would affect the shape of an ice cap.
They discovered that the undulations they observed on the ice cap’s surface matched the model predictions perfectly. These patterns were reminiscent of the depressions and raised areas found in ice sheets that lie above subglacial lakes on Earth.
The researchers used the new information to re-create a computer model that mimics the ice flow on Mars. They then tested the model to see how different amounts of geothermal heat from below the ice cap might have affected the undulations the team observed. The results were impressive, showing that the ice cap’s surface was shaped by the undulations caused by the flow of liquid water beneath it.