Mars – The Red Planet

Mars is the fourth planet from the Sun and is named after the Roman god of war. It is known as the Red Planet due to its red colour.

Mars as imaged by the Viking Orbiter taken in 1998 Credit: NASA

Mars is further away from the Sun than Earth. As such, this means that it takes longer to complete one orbit. Mars takes 687 days to orbit the Sun and the tilt of the planet is similar to the Earth. The similar tilt means that Mars experiences similar seasons to Earth but because the orbit is longer the seasons last almost twice as long as they do here. At the north and south poles of Mars are ice caps, reminiscent of what we have on Earth. They are made primarily of liquid water but during the martian winter they expand because a layer of dry ice (carbon dioxide ice) freezes across them. In the image below you can see the shrinking of the Northern Cap between October 1996 and March 1997.

Seasonal changes to the Ice cap on Mars. Credit: NASA

The atmosphere on Mars is much thinner than Earth. It is made up of 95% carbon dioxide. Other gases include argon, nitrogen, oxygen and water vapor. Temperatures on the surface of Mars range from about -140oC to 35o C, but because the surface pressure on Mars is so low, it is impossible for liquid water to be present on the surface. However, this was not always the case. There is very strong evidence that Mars was once a watery world with oceans of liquid water. Satellites and rovers sent to Mars have found evidence of erosion by rivers, deltas, gullies and dry lake beds in the Martian landscape. Some of the rovers have also found minerals such as hematite and gypsum on Mars, and these minerals normally form in the presence of water.

Scientists think that billions of years ago Mars had a much thicker atmosphere, and atmospheric pressure was sufficient to have liquid water. On the question of how Mars lost most of its atmosphere, scientists think that it once had a magnetic field that protected the atmosphere from the solar wind. The MAVEN spacecraft showed that the solar wind is still slowly stripping some of the atmosphere from Mars. The solar wind is a stream of particles that constantly stream from the Sun. Earth has a magnetic field which protects the Earth from these particles. It is thought that Mars once had one too but it shut down around 4 billion years ago. After that, the atmosphere was slowly stripped away to what we see today.

People have long speculated about Mars being habitable to life. Some of the first astronomers to view Mars through a telescope concluded that the dark patches they saw were vegetation and the long markings on the surface were canals. Today we know that there is no vegetation or canals, but there is still a question as to whether Mars could, does or ever did host microbial life. Mars is a lot more hospitable to extreme forms of life than some other places in the System System. We know from rovers, that the Martian soil contained organic compounds in the past and scientists using the Mars Express Orbiter have found a sub glacial lake under the ice at the south pole. So given that we know at least some of the building blocks for life are, or were present, it is not impossible to think that bacterial life could have lived there and maybe still does.

If it does, it would need to be underground to protect itself from the ultraviolet radiation coming from the Sun. There have been pockets of methane and formaldehyde observed by orbiters above Mars, and some people think this could have been produced by life beneath the surface. Methane is quickly broken down in the Martian atmosphere, so when these pockets are observed we know that it has only been recently produced. It is probably more likely that these pockets are created by some form of volcanic or geological activity rather than life. Even if life doesn’t exist on Mars today, it is possible it did in the past when conditions were more suitable, but for the moment we just don’t know.

Mars Pathfinder mission on the rocky red surface. Credit: NASA

There is a wide variety of surface features on Mars such as polar caps, mountains, river valleys, dry lake beds, craters, caves and volcanoes. Mars is home to the one of the highest volcanoes in the Solar System called Olympus Mons and is 22 km high. Features on Mars are named in a variety of ways. Small valleys are named after rivers, while large valleys are named after the word for star or Mars in various languages. Craters larger than 60 km are named after deceased scientists and writers who contributed to the study of Mars. Craters smaller than 60 km are named after towns or villages with populations less than 100,000. There are a number of craters on Mars named after towns and villages in Ireland such as, Beltra, Dromore, Fenagh, Lismore, Louth, Navan, Tara and Wicklow.

Mars can experience weather on the surface. Dust Devils are common and are similar to tornadoes on Earth but get their name from the red dust they pick up as they spin. Mars can also have huge dust storms that can encircle the planet for months at a time. This causes particular problems for robotic spacecraft on the surface as they depend on solar power for electricity. In 2018 a huge planet wide dust storm developed and NASA lost communication with the Opportunity rover. The rover had been designed to last 92 Earth days on the martian surface but ended up lasting 15 years before finally succumbing to the 2018 dust storm.

Mars is easily spotted in the night sky from Earth and at the moment it is visible in the East after 2.30am. When the planet is well positioned, it is possible to see a lot of detail on the surface, such as the ice caps. This led to a lot interest in Mars in the early days of observation, imaginations went wild and it was the topic of many science fiction stories. The first spacecraft to fly by Mars was Mariner 4 in 1965. Since that there have been dozens of missions sent to Mars. Some were orbiters, some landers and some were even rovers that drive around the surface. Some of these landers and rovers were like mobile science labs. They had the ability to dig up dirt, load it into the spacecraft and carry out experiments on it.

Mars is the most studied planet beyond Earth and this isn’t going to change anytime soon. At the time of writing there are a number of planed missions to Mars. All going well, this July will see the launch of a Chinese rover to Mars called Tianwen-1, the first mission to Mars by the United Arab Emirates called the Hope Mars Mission and NASAs Perseverance Rover. The Perseverance rover will also carry a drone to Mars called Ingenuity. The drone is a technology test and will be used to scout locations for the rover. The rover will also collect samples and store them onboard. It is hoped that in the future NASA and the European Space Agency (ESA) will collaborate on a mission to return the samples to Earth.

Ingenuity helicopter drone which will fly to Mars aboard Perseverance. Credit : NASA

The ESA and the Russian space agency Roscosmos was due to launch a rover to Mars called the Rosalind Franklin Rover this July but due to technical difficulties and the COVID-19 pandemic, it has been postponed to 2022. The Mars Orbiter 2 is a mission by the Indian Space Agency due to launch in 2024. In the future we may even see humans on the surface of Mars but there are a number of challenges that must be overcome before this is possible. Space X has previously said they want to launch a mission to Mars by 2024 but most people think that this is too optimistic. NASA are currently targeting the 2030s for a manned mission to the Red Planet. Mars is a fascinating world and will likely be the first planet to be explored in person by human beings.

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