Solar System -- Mars - Part 1

Note: This article is in two parts. The first one is on the planet and the second article is on travel to Mars.

The information provided in this article is not exhaustive. Please ask questions related to the planet and its missions. This way I can add more information and improve the thread.

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MARS

Image source: nasa.gov​

Of all the planets in our solar system, none has captured our interest and provided fodder for our imagination than our closest outer neighbor, and the fourth planet from the Sun - Mars.

About half the size of Earth, Mars got its name from the Roman God of War, due to its red appearance. Mars is red because iron minerals in the Martian soil are oxidized giving the planet and its dusty atmosphere the red color.

Mars spins on its axis just as Earth does and takes about the same time – 24 hours and 39 minutes. A day on Mars is called a “Sol”.

It has about 1/10 the mass of Earth

This terrestrial planet is an average 228 million kilometers from the sun - 1.52 AU. We say “average” distance because Mars has an eccentric and an elliptical orbit. At aphelion (farthest point) it is 249 million km and at perihelion (closest point) it is 206 million km from the sun.

It takes 12 minutes for sunlight to reach Mars.

How far is Mars from Earth?

This distance varies. Here’s how.

• We all know that Mars is further away from the Sun. Therefore its orbit lies further and takes much longer to complete a single lap. In fact it takes Mars two Earth years and two Earth months to complete a single orbit.
• Both Earth’s orbit and Mars’s orbit are ellipses (oblong).
• So when Mars is at its perihelion (closest point to the Sun) and Earth is at its aphelion (farthest point from the Sun), Mars and Earth will be the closest – about 55 million kilometers.
• It is interesting to know that this has never happened in history. The closest the two planets have ever come has been about 56 million km.
• When both Earth is at its aphelion and Mars is also at its aphelion, they will be on the opposite sides of the Sun and this will be the farthest distance they will be apart – about 401 million km.

image source: Rutgersprep.org​

Origin of Mars
Mars formed about 4.6 billion years ago along with the Earth and the other planets in the Solar system, and was hot.

• As the heavy iron melted and sank to the center to form the core the lighter silicates formed the mantle and the crust.
• The young Mars had numerous active volcanoes which spewed lava, water, and carbon dioxide into the atmosphere.
• It is believed that Mars once had a thick atmosphere and it was warm enough on the planet to support the existence of liquid water.
• Today Mars has a very thin atmosphere made up mostly of Carbon dioxide, Nitrogen, and Argon.

Why thin atmosphere?

NASA’s MAVEN (Mars Atmospheric and Volatile Evolution MissioN) has determined that the Martian Atmosphere was stripped by strong Solar winds.

Findings reveal that every time there was a strong solar storm, a huge chunk of Martian atmosphere would be wiped off. Scientists believe that billions of years ago a large amount of the atmosphere must have vanished when the Sun was younger and had more frequent solar storms.

Question: If solar storms could strip away Mars’ atmosphere how is it that Earth does not lose its atmosphere to solar winds?
Ans:That’s because we are protected by the magnetic field.

Mars does not have a magnetic field – today.
About 4 billion years ago the planet did have a magnetic field, traces of which are detected in the Southern Hemisphere.

Why no magnetic field?

The magnetic field generated by Earth is quite complex in nature. The simple explanation would be that the hot core and its rotation makes our Earth a huge electromagnet.

However, Mars’ core, because of the planet’s small size, cooled down fast, and was unable to generate the electromagnetic currents required to maintain the super magnetic field to protect itself from the solar winds.

Question:Well, if lack of magnetic field is the reason for loss of atmosphere, how does Venus, which also does not possess a magnetic field have such a dense atmosphere?
Ans: That’s because of Venus’ dense gravity helps it to hold on to its atmosphere.

Another reason why atmosphere on Mars was stripped off is gravity. Mars’ gravity is only 62% that of the Earth’s. A 50kg person on Earth would weigh 19kg; that light.


image courtesy: nasa.gov

Therefore its atmosphere was easily blown away by the strong solar storms that come at a rate of 1000km/hr.

Feet in spring and head in winter!
Since Mars has a much thinner atmosphere than the Earth, heat from the sun easily escapes this planet. If you stood on the surface of Mars on the equator at noon, it would feel like spring at your feet (24 degrees C) and winter at your head (0 degrees C).

WATER

Water does not exist on the planet today as rivers or streams. However, Hydrogen rich deposits and land structures at many different areas where Mars rovers have explored indicate that water may have existed once upon a time.

Below is a picture that shows land shaped as a result of water flow


image courtesy: www.nasa.gov

It is believed that Mars experienced great floods about 3.5 billion years ago. Where the water came from or where it went, nobody knows, yet. Scientists are hoping that the different discoveries from the various missions will help them solve this mystery.

At present evidence of water is found mainly in icy soil in the Polar Regions and thin clouds.

In 2015 there developed a hypothesis that briny water flows seasonally but does not stay on the surface for long.

The below picture shows the timeline between water flow and the new gully deposits.

image courtesy: www.nasa.gov

Martian Axis

Though Mars axis today is tilted at 25 degrees (Earth 23.5), Mars’ axis is not stable like our Earth’s. Over billions of years, Mars’ axis has tilted at many angles.

It is quite possible that when the axis was tilted at a more extreme angle ice caps grew on the planets equatorial region. This may explain why a lot of underground water is discovered beneath the surface at the equatorial region than at the poles.

If water was present on Mars long ago this leads to the next question: Did life in some form exist on Mars also?

There is still no evidence that life existed or exists on Mars. MOM- India’s Mangalyaan mission is to find if microorganisms are present on Mars. The mission was sent after observations of spurts of methane being released into the Martian atmosphere. Microorganisms generally produce methane. Mangalyan's mission was to determine if the methane is organic or a product of a chemical reaction. Till today no microorganism existence has been confirmed.

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Some more information on Mars

• Mars has no rings. However, it is believed that in about 50 million years, Mars will have a ring.
• Right now Mars has two moons, Phobos and Deimos.
• These are not round like our moon. They are actually potato shaped.
• Scientists think they could be strays from the nearby asteroid belt. It is also believed that these two will never become round because of their small mass. Therefore they have too little gravity to shape themselves up into a ball.
• Of these two natural satellites, the larger, Phobos is slowly moving towards Mars. It is expected to crash into the planet 50 million years from now and the impact could cause a ring from the resulting dust particles.

Mars has some records to its credit in the Solar system.

It is home to the largest volcano in the entire solar system. ​

Olympus Mons, towers at a staggering height of 27,000 meters.


image source: jpl.nasa.gov

This is thrice as tall as Mt. Everest. The base of the long dormant volcano is about the size of the state of Arizona.
Here is a comparative illustration:


image source: Canadian space agency(space.com)

It is home to the longest, deepest, and widest Canyon too.​

Valles Marineris. Valles Marineris is long enough to stretch from California to New York -- more than 4,800 km (Grand Canyon is 446 km). It is 7 km (Grand Canyon -1,600 m) deep and 320 km wide (Grand Canyon – 30 km).


image source: wikipedia

Below is the comparative illustration to the Grand Canyon;

image source: UVA

This planet has been bombarded by numerous meteors since its formation that in addition to these two there are also lots of interesting meteor craters and rocks.

Mars’ skies.

Sunlight on Mars is less intense due to the farther distance compared to Earth.

Daytime sky in Mars is a butterscotch (yellowish-brown) due to the presence of iron oxide (magnetite) particles in the atmosphere.

At sunset, though the upper sky is pinkish red, at the lower region, just around the sun, the sky appears blue. This is because the fine Martian dust near the surface of the planet scatters the blue light forward and produces a blue sunset.


Image source: nasa.gov (Curiosity rover)

Mars Seasons

As Mars axis is tilted away from the sun Just as Earth’s, it experiences all the four seasons just as we do on Earth.

However there are some differences- there has to be, right?

Since Mar’s year is 26 months long and it has an eccentric orbit, and a slight difference in its tilt, the seasons duration vary. The Southern winters are long and extremely cold while the northern winters and warm and short.

Many more interesting features on Mars can be observed.

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...contd. from previous post.

Here are some interesting features from Mars.
All images - credit to nasa.gov.

Niagara falls on Mars


Image source - nasa.gov

The Ganges Chasma


Image courtesy: nasa.gov

Sulfate deposits



Dunes and Winds



And finally my favorite: Rover climbing atop a mountain.
Rover is the small blue thingy in the center of the picture. (circled)

Image courtesy: nasa.gov.

Mars indeed is fascinating.

Thank you

Information sources: NASA, Universe Today, Space, and various discussions with NASA scientists.

 

Thank you @PavithraS
Happy to know you are going to share this with your son.
How old is he?

 

Thank you @Nonya
That was informative.

Should have?