Universe Today

As with the rest of the planets in the Solar System, Mars is believed to have formed out of the primitive solar nebula 4.5 billion years ago.

Instead of condensing directly, from dust particles to planet, Mars and the rest of the terrestrial planets probably started out as a collection of small particles. Dust particles clumped together to form larger and larger objects. Dust became sand, pebbles, rocks, asteroids, and eventually planetoids. The formation of Mars happened when these particles all came together.

The energy from all these collisions heated up planet Mars, giving it a molten core and volcanic activity. We can see evidence of the end of the planetary formation period because of the impact craters strewn across the surface of the planet. This period was called the late heavy bombardment period, and all the planets in the Solar System were devastated too.

Astronomers think that Mars is relatively small because Jupiter finished its own formation a little earlier, and scooped up most of the available material. The gravity from Jupiter also seems to have prevented the formation of another planet in between Mars and Jupiter; instead, we’ve just got the asteroid belt.

Although Mars doesn’t have active plate tectonics, and its volcanism ended millions of years ago, the planet is much more similar to Earth and Venus, and different to the Moon and Mercury. Mars is the only other world in the Solar System that has a transparent atmosphere, and surface conditions that could be considered somewhat habitable.

Here’s an article from Universe Today about why Mars might be so dry. And more information about where the water went on Mars.

Additional information about the history and formation of Mars. And even more information here.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

The orbit of Mars is the second most eccentric in the Solar System. Only Mercury’s orbit is more eccentric. At perihelion Mars is 206,655,215 km from the Sun and at aphelion it is 249,232,432 km distant. That is a variation of of just under 42,600,000 km. The average distance from Mars to the Sun (called the semi-major axis) is 228 million km. It takes Mars approximately 687 Earth days to complete on orbit. The orbit of a planet varies in relation to the gravitational influences of the bodies around it, so the eccentricity can change over time. AS recently as 1.35 million years ago, Mars was in a nearly circular orbit.

Mars, like all planets in the Solar System, is tilted along its axis(axial tilt). For Mars, the axial tilt is about 25.19 degrees. This tilt is similar to Earth’s, so Mars has seasons like ours. The Martian seasons are longer because a year on Mars is nearly twice as long as an Earth year. The dramatically changing distances between Mars’ aphelion and perihelion means that the seasons aren’t balanced like Earth. Mars is at its closest when its southern hemisphere is tilted towards the Sun. So the southern hemisphere experiences hotter summers than the northern hemisphere.

The orbit of Mars allows it to approach Earth at varying distances. It is easiest to observe when it is at its closest approach. Opposition occurs when Mars’ geocentric longitude is 180° different from the Sun’s. Opposition can occur as much as 8½ days before or after closest approach. The distance at close approach varies between about 54 and 103 million km due to their position in their orbits. The last Mars opposition was on January 29, 2010. The next will be on March 3, 2012(about 100 million km). The average time between the successive oppositions(synodic period) of Mars is 780 days. Mars made its closest approach to Earth in nearly 60,000 years(55,758,006 km) on August 27, 2003. While this was a record, it was only slightly closer than other close approaches.

The orbit of Mars is well understood and has been observed, and documented, for thousands of years. The planet’s short period of apparent retrograde motion was noted as early as 1534 B.C. After reading and understanding the planet’s orbit, you should research more about its atmosphere, gravity, and exploration. Only then will you have a grasp of a few of the mysteries surrounding the Red Planet.

Here’s an article about Martian ice ages in the past, related to tilt, and another about mid-latitude glaciers on Mars.

Here’s more general information about Mars. And here are some pages from NASA about the Mars Phoenix Lander mission.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Source:
NASA

Mars is named after the Roman god of war. Many believe that ancient peoples associated Mars with bloodshed and war because of its red color. The Romans were not the only society to associate the planet with bloodshed. The ancient Babylonians called it Nergal, after their god of fire, war, and destruction. In keeping with the planet’s association with the god Mars, its symbol is a circle with an arrow pointing outwards from its right corner. This is meant to represent Mar’s shield and spear.

That information is not nearly enough to satisfy anyone’s interest in the Red Planet, so here are a few interesting facts about Mars and its environs.

The largest mountain in the Solar System is on Mars. Olympus Mons is 27 km tall. It is a shield volcano that was able to erupt for million of years because Mars does not have tectonic plate movement. This allowed the same volcanic hotspot to erupt undisturbed until the giant mountain was formed.

The chemical symbol for iron is the same as the astronomical symbol for Mars. This is fitting, since the planet gets its reddish appearance from the iron oxide in the dust on its surface.

A year on Mars lasts 686.98 Earth days or 1.88 Earth years. There are four seasons throughout the year like here on Earth, but each season is longer than a typical Earth season.

Mars is full of water. Not liquid water like we see here on Earth, but water ice under the surface and at the bottom of craters. There is even evidence that there may be ice inside of caves on the Martian surface. These deposits are safe from the solar radiation that bombards the surface, so they are able to stay in place.

Mars does not have a magnetic field at this time, but spacecraft have detected residual magnetism in rocks on the surface. That would suggest an active magnetic field millions, if not billions, of years ago. Scientist believe that the core of Mars has become too solid to rotate and is no longer capable of generating a dynamo effect. A dynamo effect is essential in producing a magnetic field.

These are just a few of the interesting facts beyond who Mars is named after. Pay special attention to information generated by the Mars Express spacecraft. It has turned up a great deal of interesting data on, and under, the Martian surface.

In case you’re wondering, here’s how Jupiter got its name.

Here’s some historical information on Mars, the god of war, and more on Ares, the Greek version of Mars.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:
NASA
Case Western Reserve University – Astronomy

The diameter of Mars is 6,792 km. That makes the Red Planet about 53% of the diameter of Earth. In addition to a smaller diameter, Mars has only 10% of Earth’s mass. Those are interesting pieces of information to have, but only give a small picture of what Mars is like. Here are some more facts about Mars.

The gravity on Mars is only 38% of that on Earth. That would present some interesting issues for any visitors to the planet as well as some challenges to long term colonization. The low gravity can also be connected to the near absence of a Martian atmosphere and the cold, dry environment. Gravity helps atmospheric gases to cling to a planet’s surface. Mars can only cling tenuously. What atmosphere that is present is high in carbon dioxide, so if the planet retained more of it, the surface would warm quickly through a greenhouse effect. The greenhouse effect would melt the subsurface ice that the Mars Express spacecraft has found, thus moistening the surface. There are many indications from different spacecraft that Mars was at one time a warmer, wetter world.

Mars is often perceived as a dead planet. Scientists had begun to accept that possibility until methane was detected in its atmosphere. The methane is most likely from a geologic source, but it has to be a large source. Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so discovery of substantial methane indicates that an ongoing process is releasing it. The presence of the gas is of interest to scientists because organisms release much of Earth’s methane; however, other processes, like oxidation of iron, also release methane.

Mars lacks any tectonic plate movement. That may allow the source of the methane to release it in plumes. The lack of plate tectonics is also the reason that the largest mountain in the Solar System was able to form. Olympus Mons, on Mars, is a shield volcano that is 27 km tall and about 550 km across. The absence of plate tectonics allowed a single hotspot to pour molten material onto the surface uninterrupted for millions of years.

You started out wondering what the diameter of Mars is and, now, you have several interesting facts to ponder. Be sure to double check our facts on the NASA website and, hopefully, you will find much more to pique your interest.

And just in case you’ve heard this hoax going around, Mars will never look as big as the Moon in the sky. That’s a myth that got started back in 2003, and just won’t go away.

Here’s a 1928 research article where the diameter of Mars was accurately calculated. And then the sophisticated gravity measurement instrument on board NASA’s Mars Reconnaissance Orbiter, that can make extremely accurate gravity measurements of Mars.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:
NASA: Mars
Harvard University
NASA: Mars Methane

”Does Mars have seasons?” is an easy question to answer. Yes, Mars has seasons. The planet experiences all four seasons that the Earth does, but, since the year is longer on the planet, the axial tilt is different, and Mars has a more eccentric orbit than Earth, the seasons are not the same length as each other or the same in each hemisphere. Why does Mars have seasons? Because, like Earth, its axis is tilted away from the Sun.

On Mars, in the northern hemisphere to be exact, spring is the longest season. The Martian year is nearly twice as long as an Earth year(1.88 years), the seasons last longer as well. Here is how a Martian year in the north breaks down: Spring…7 months, Summer…6 months, Fall…5.3 months, and Winter…just over 4 months. Even in the summer months it is very cold. Temperatures at the height of the season may not top -20 C. In the south the temperatures can be as much as 30 C warmer during the same season. The great fluctuations in temperature and the difference in warmth between hemispheres can cause huge dust storms. Some can affect just a small area, while others can cover the entire planet. The larger storms usually occur when the planet is near its aphelion(closest point to the Sun). When there are global dust storms there is no way for scientists to visualize the planet’s surface.

Now that you have the answer to ”does Mars have seasons?”, you might wonder if the planet has always had the same climate. Most scientists doubt it has. Scientific evidence suggests that the planet has seen warmer and colder periods over its existence, much like Earth has. A radar instrument on the Mars Express has turned up water ice, a mineral mapping instrument has discovered chemicals formed in a wet environment, and its camera has picked out features on the surface formed by running water. The cameras also show a huge valley, Kasei Valles, that was probably carved by a gigantic glacier. Additional research has shown evidence of glaciers at varying latitudes. This would seem to indicate that the planet formerly had a different degree of axial tilt, which would have made for a much different environment and potential seasonal variations.

Mars does have seasons. They are not the same as the seasons the planet experienced millenia ago and may not be the same in the future. Earth has seen the same climate changes. Planetary evolution is ongoing, hopefully the spacecraft on and around the planet will tell us more, soon.

Here’s an article describing Spirit surviving 1000 days on Mars, going through all the seasons. And another on the discovery of mid-latitude glaciers on Mars, evidence that the planet was much more tilted in the past.

Here is some great information from the Adler Planetarium about the Martian climate and seasons. And some more detailed information from Malin Space Science Systems.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:
NASA
Geosociety.org