Mars: The Seasonal Repercussions of the Martian Planet
By: Trey Fritz, Nic Trischuk, Brett Weiman, Hunaina Shah, Mikki Atienza
Mars, the fourth planet from the sun, is also the second smallest planet in our solar system. Its climate has important similarities to Earth such as the polar ice caps, seasonal changes and the presence of weather patterns. While Mars’ climate has similarities to Earth’s, there are also important differences, such as much lower thermal inertia and an atmosphere difference which makes it a prime target for exploration. On Earth, we experience four seasons, spring, summer, autumn and winter. These seasons can be broadly applied to Mars as well. The Seasons on Mars are influenced by the tilt of its axis and by its distance from the Sun. Earth is always about the same distance from the Sun, but the orbit of Mars is more elliptical, resulting in more energy from the sun at certain points along its orbit, making seasonal changes quite significant. There is the familiar winter, spring, summer and fall on Mars with an addition of two seasons, aphelion and perihelion, which occur because of Mars’ highly elliptical orbit. Throughout this project, we aim to compare and contrast each season on the “Red Planet” and analyze how they change various properties of the planet.
So we need to ask ourselves, how do we know what the effects of the different seasons of Mars are and how do they apply to its atmosphere, physical landscape, possibilities of life, and future colonization efforts?
Video of Mars’ Orbit:
Fun Facts of Mars
- Mars got its name from the Roman god of war and agricultural guardian.
- Mars is only 10% the mass and 15% the volume of Earth, however, it has nearly identical landmasses since 70% of Earth’s mass is water.
- Mars’ surface has ~37% the gravity found on Earth.
- Mars is home to the tallest mountain known in our solar system, measuring a total of 21 km high and 600 km in diameter.
- Mars’ orbital radius is 227,840,000 km.
Factors Affecting Seasons on Mars
Every planet in our solar system has seasons like Earth. But the seasons that occur on other planets are different from the traditional spring, summer, fall and winter weather that we experience on Earth. The factors that that affect the weather on Mars are:
1) The tilt of a planet’s axis – Mars rotates on its axis, completing one revolution every 24.5 hours. The axis of Mars is tilted at 25 degrees and 12 minutes relative to its orbital plane about the Sun. This produces seasons on the surface of Mars. It completes one orbital revolution around the Sun every 1.88 Earth years. (6)
2) The shape of its orbit around the sun– During a Martian year, the planet’s elliptical orbit exposes it to the sun’s energy at varying proximities and intensities. This means seasons last different lengths of time in each hemisphere. Its orbital motion is slowest when it is at aphelion (the farthest point from the Sun) and fastest at perihelion (the closest point to the Sun). This makes Martian seasons vary greatly in duration compared to those on Earth. Seasons change roughly every six months, with northern spring and fall lasting 171 Earth days, northern summer being 199 days in length, and northern winter being only 146 days. (15)
3) The presence or absence of a significant atmosphere– Mars has a thin atmosphere which is about a hundred times less than Earth’s and composed almost entirely of carbon dioxide with a few traces of nitrogen, oxygen, and water vapor, which contribute to the extreme temperature variations. The temperatures on Mars never go above 20°C at noon on the equator. It’s more likely to be colder most of the time, with temperatures as low as -140°C during polar wintertime. (2)
4) Its average distance from the Sun and the length of its day– Mars’ distance from the Sun varies between 1.38 and 1.67 AU over the Martian year (twice of Earth’s year). This large variation, combined with an axial tilt slightly greater than Earth’s, gives rise to seasonal changes far greater than on Earth. In winter the global atmospheric pressure on Mars is 25% lower than during its summer. This happens because of the eccentricity (a parameter that determines the amount of orbit within another body and how it deviates from a perfect circle) (22) of Mars’s orbit and a complex exchange of carbon dioxide between the Martian dry-ice polar caps and its CO2 atmosphere. Around the winter solstice, when the North Pole has tilted away from the sun, the northern polar cap expands as carbon dioxide in the polar atmosphere freezes. At the other end of the planet, the southern polar cap melts, giving CO2 back to the atmosphere. This process reverses half a year later during the summer solstice. But Mars is 10% closer to the Sun in southern summer than it is in northern summer. At the time of the winter solstice, the northern polar cap absorbs less CO2 than the southern polar cap absorbs half a year later. The difference is so great that Mars’s atmosphere is noticeably thicker during northern winter (7).
5) Climate change – Climate change on Mars is an often talked about topic. Its atmosphere is about 100 times thinner than Earth’s (14). To help understand this difference, think of Earth. Earth contains elements such as Nitrogen, Carbon Dioxide, and Oxygen, among others, to help sustain life forms. It also protects us from things like radiation, while also allowing for heat to stay fixed at the surface of the planet. Earth is not known for having a thick atmosphere itself, it is actually rather thin. Now imagine Mars, the pressure and amount of gases are lower than Earth’s, while also containing far more cold areas to account for the lack of protection and fixed heat. Thes atmospheric conditions result in the planet being on average around -80°F (roughly -62°C) and reaching close to -125°C during the winter (14).
from the Sun
(millions of km)
|Mars||227.9||24.5 hours||25.2||0.09||Elliptical||Very thin||
Basic Summaries of the Seasons on Mars:
On Mars, “Sols” or “Martian Earth Days” last approximately 39 minutes and 35 seconds longer than a day on Earth, making one Martian year last 668 sols (or 684 Earth days). Although we are able to measure “days”, Mars does not have any uniform measurable months, instead, scientists use solar longitude (Ls) to mark times in a Martian year (5).
Perhaps one of the most interesting traits of Mars is the altering appearance of the surface while it undergoes seasonal shifts which are observable by telescope. These changes are often referred to as “Albedo changes” (12). In order to get a true appreciation of these surface changes, it is ideal to observe the planet over a course of 7-8 successful oppositions (around 15-17 years).
Similar to summer on Earth, summer on Mars occurs when the portion of the planet tilted towards the sun is at its closest point. The summer solstice on Mars occurs at a solar longitude of 90॰. During Martian summer, temperatures can rise up to 20॰ C during the day (at the equator) but will drop to around -73॰ C (3). The great increase in temperature leads to a significant increase in energy present within Mars’ atmosphere causing extreme dust storms that can cover large regions of the planet, sometimes even the whole planet, for weeks to months (4). Summer is about 6 months long, comparable to the planets’ autumn.
Areocentric longitudes of Mars will be 0° to 89° while the southern hemisphere is in autumn and the northern hemisphere is in spring. The planets most famous features are arguably its northern and southern polar caps. As on earth, the planets axial tilt greatly affects these polar caps by either shrinking or expanding them; during autumn as one would expect, the temperature drops and the polar caps display a shrinkage that is observable by even modest size telescopes (12). Autumn is about 6 months long, around the same length as summer in the northern hemisphere.
The vernal equinox (start of northern spring) occurs at a solar longitude of 0॰ 5. The southern hemisphere of Mars has a warmer, shorter spring than the north, as Mars is the closest to the sun towards the end of the southern spring. Changing from the extreme colds of Mars’ winter, spring will have some drastic effects on the physical landscape. During spring of either hemisphere, the polar ice caps begin to thaw and decrease in size. Because Mars’ atmosphere is so thin, the carbon-dioxide ice skips becoming a liquid and goes straight to being a gas. This effect causes a serious increase in pressure under the ice, cracking it and eventually causing the gas to burst up, creating scattered patterns across the landscape (7). Spring is the longest season lasting about 7 months in duration.
During winter near the poles, the temperature can get down to -195°F (-125 °C) which is a drastic change when considering the temperatures near the equator during summer can be as high as 20°C. Seasonal length varies due to the planets eccentric motion around the sun, meaning that winter is only 4 months long. At the coldest of temperatures in the southern hemisphere, carbon dioxide snow clouds form, some of which become substantial enough to produce snow (3).
These are not traditional “seasons” but rather additional planetary changes that cause several physical effects on the planet’s landscape. These planetary changes occur because of Mars’ highly elliptical orbit. This means that because Mars’ orbit is more elongated, it will get much closer to the sun at some points of the year (4).
The differences in orbital speed and kinetic energy of Mars during these seasons can be explained by Kepler’s Second Law – Kepler’s second law of planetary motion describes the speed of a planet traveling in an elliptical orbit around the sun. It states that a line between the sun and the planet sweeps equal areas in equal times (9).
Perihelion occurs when the planet is at its fastest orbital motion. Since it is closest to the sun at this point, it will get about 40% more energy in the summer during this period which is an important point to note as it could be a large factor affecting changes in the planet’s surface conditions; being much hotter during the day than if it wasn’t during aphelion. Kepler’s second law can explain how the planet has the most kinetic energy and is, therefore, traveling at its fastest at this point. Full global dust storms tend to occur approximately every three Martian years and always occur during Mars’ Perihelion.
According to Mars’ most recent Perihelion (Oct. 29, 2016), the planet reached a distance of 1.38 AU from the sun (25).
Mars’ orbital motion is slowest when it is at aphelion (the farthest point from the Sun).
This is also explained by Kepler’s second law, indicating that the planet has its lowest kinetic energy at this point. During its farthest moment from the sun, Mars’ reaches a distance of 1.67AU (25). A major implication of Mars being further away is that it will be receiving much less energy from the sun than during other parts of the orbital year; such as during perihelion which is the opposite condition.
Structural Changes Through the Seasons
The composition of Mars’ surface is quite unique. Its outer layer, the crust, is mainly composed of dust and rocks of a rusty color, due to the prevalence of oxidized iron. This fine, dusty crust that we are familiar with observing is simply a covering of the actual crust which is composed of several common minerals such as sodium, potassium, magnesium, and chloride, measuring in at approximately 50 km thick. These crust layers will be the ones most detrimentally affected by seasonal changes (14).
With the amount of cold air on Mars, there is also warm air flow. This warm air flow is caused by particles on the planet that absorb sunlight (14). When these two air flows mix, along with the changes in pressure, it seems to cause extreme winds. This, in turn, can initiate landslides of the dusty crust, speeding down the planets slopes reaching upwards of 725 km/h. These landslides result in visible dunes and extreme elevations and depressions on the surface (14).
These fluctuations of temperature causing the extreme winds also cause detrimental dust storms. The formation of these dust storms is similar to the formation of the average storm on Mars. Although the majority of these dust storms are not overly intense, because the dusty crust contains oxidized iron, the dust particles are slightly electrostatically charged which would pose further problems for the possibility of solar power during colonization (15).
These dust storms leave a plethora of intricate designs carved into the dusty crust. These are also caused by smaller dust devils that, although do not have the same magnitude as a full dust storm, can still cause changes to the structure of the crust. These dust devils have been observed to reach up to 800m in height (15).
As previously mentioned, Mars has two polar ice caps composed of frozen carbon dioxide. During the planet’s northern and southern summer, the ice caps melt mainly into water ice but the thin layer of carbon dioxide ice remains. The subtle yearly changes in the planet’s tilt and orbit cause variations in the planets seasonal climates which will affect their “ice ages”. Through the melting and subsequent freezing along the years, the northern ice caps have created boundaries, composed of years of accumulation and erosion of layers of ice. This recent discovery has led scientist to the conclusion of being able to date and pinpoint the creation of the glaciers and the periods of regrowth (17).
New research has shown that beneath regions of the northern ice cap, scientists have observed impact craters and even more carbon dioxide ice locked deep into the ice cap. These changes highlight the effects of the planet’s tilt precession (18). These new discoveries will surely lead to more clues as to the changes in Mars’ climate.
Factors affecting Colonization
1) Vegetation– After learning about how Mars behaves seasonally, it seems that there would be low potential for vegetation. The significant amount of cool air, along with a large number of storms, has proved to be a major contributor to the continued lack of water and hydrogen on Mars (14). This environment is not suitable to support plant life and is shown by the lack of any visible vegetation on the surface of the planet. Although six satellites have been placed into orbit around Mars and several missions have been scheduled (20), these satellites and other research missions to the planet are very important as more information will be gathered about Mars’ atmosphere and could reveal other factors or details that are currently unknown. The continued analysis of Mars’ seasons over long periods of time will help us discover how this planet changes structurally as well. Throughout the research, Mars seems to be much different from Earth when comparing seasons, atmosphere and other structural developments; though there are similarities in the overall trends.
2) Terraformation– An important aspect to consider when approaching the possibility of the colonization of Mars is the cost and scope of terraforming. Terraformation involves processes and techniques that would transform the Martian atmosphere to make certain areas of the planet hospitable to life and sustainable in the long run. The atmosphere itself is affected by the solar winds from the Sun (8). Over time it has worn and shed chunks of the atmosphere causing Mars’ to lose its electromagnetic field and thus exposing the planet to radiation. Proposed methods include the use of ammonia ices to unleash a greenhouse effect on Mars, resulting in a thicker atmosphere which would, in turn, provide warmer temperatures and breathable atmospheric gas for humans (20). Another idea proposes the covering of certain surface areas with a dark substance, such as low albedo material on the polar ice caps. This would theoretically allow for the ice to absorb more heat energy, melt, and contribute to a more sustainable atmosphere through the addition of humidity (13).
3) Habitation – The atmosphere on Mars provides very little protection from extreme radiation. The harsh climate and seasons combined with this exposure to radiation present a problem regarding adequate and safe shelters for possible colonists. The process of building these homes or possibly sending them to Mars must also be feasible as well as sustainable. With these conditions in mind, one can start forming ideas of what a proper habitat would look like and be composed of in order to fulfill the need for protection from radiation as well as the harsh climate/conditions which were noted in the above sections on each season. Water, in the form of ice beneath the surface of Mars, works as a great shield for galactic cosmic rays, therefore the idea to burrow into Mars and form underground settlements was proposed. Excavating would mean the use of heavy machinery which would have to be transported to Mars, making it a costly and impractical choice. As of late, however, NASA has been working on plans for the “Mars Ice Dome” which would involve the use of an inflatable frame that can act as a mold once filled with water which eventually turns into ice. This eliminates the problem of transporting large and heavy machines while still making use of the protection the ice beneath Mars’ surface would provide the inhabitants (17).
Mars is a bewildering planet. The extraordinary information it can teach us, the mesmerizing mysteries it proposes to us, and the endless possibilities for our future all compose the identity of this amazing planet. If we try and compare the “Red Planet” with our home planet Earth, there are many surprising similarities you might not expect; yet the differences are even more numerous and complex. Is it possible for mankind to develop a strong enough understanding of Mars’ seasonal changes or its radically different atmosphere and landscape in order to explore and pursue future colonization? For now, that remains a mystery, but with time and many more years of research maybe that question could be answered. Whenever you look up to the stars during a clear night sky, just ask yourself, “Could there be another planet out there, that one day, someone will call home?”.
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