About Mars

Type Rocky planet
Size (diameter) 6791 km, or about half the size of Earth
Mass 6.417 × 1023 kg, or about 10% the mass of Earth
Length of a year (orbital period) 687 days
Number of moons Two: Phobos and Deimos
Average distance from the Sun 227,939,200 km
Temperature Between -140 and 30 degrees Celsius

Credit: NASA


Mars is the fourth planet from the Sun in our solar system. Scientists believe that all of the planets were created just over 4.5 billion years ago. The solar system began as a large cloud of gas, dust, and ice, which collapsed into a spinning disc. The Sun was formed at its centre and particles began sticking together along rings in the disc – leading to the formation of the planets.

Orbit and rotation

A year on Mars – the time it takes for the planet to orbit the Sun – is nearly twice as long as a year on Earth. However, the planets rotate at a similar frequency: a day on Mars (known as a sol) lasts about 24 hours and 40 minutes in Earth time.

Mars is tilted by about 25 degrees, which means that the red planet has four seasons, too – each twice as long as Earth's!


Mars is known as the "red planet" due to its reddish hue caused by oxidized iron (or rust) on the planet's surface.

The tallest mountain in the entire solar system, Olympus Mons, is on Mars. This extinct volcano is nearly 22 km tall – roughly two and a half times the height of Mount Everest.

Valles Marineris is a massive canyon system that stretches over 3,000 km across Mars's surface – about the distance between Montreal and Calgary! Plunging about 8 km deep, and often referred to as "the Grand Canyon of Mars," Valles Marineris makes the red planet home to the largest known canyon in the solar system.

This composite image captured by the Viking Orbiters 1 and 2 shows the intricate canyon network just below the planet's equator. (Credit: NASA/JPL-Caltech)

Is there water on Mars?

The search for water on Mars dates back to the s. In , Italian astronomer Giovanni Schiaparelli observed a network of lines on the surface of Mars, which he called "canali" in Italian. The mistranslation as "canals" in English fuelled speculation about the possibility of both flowing water and intelligent life on Mars.

Since then, planetary flyby missions, improved imaging techniques, and data collected by orbiters, landers, and rovers have given scientists a better understanding of the Martian landscape.

Water ice was found on the north and south poles of Mars, much of it underneath glaciers of frozen carbon dioxide. However, a small amount of water exists in Mars's thin atmosphere: Canada's meteorological station on the Phoenix mission was the first to detect snow, which vaporized before it hit the ground.

A rich past

Since liquid water cannot currently exist on the surface due to Mars's low atmospheric pressure, traces of ancient riverbeds and lakes imply that a vast quantity of liquid water may once have existed in the presence of a denser atmosphere.

Mars also used to have a global magnetic field, but scientists believe the planet lost it about 4 billion years ago. Some evidence suggests that ancient Mars may have been similar to Earth, and may have harboured the right conditions for life.

A colour panorama taken of the surface of Mars by NASA's Mars Pathfinder mission in . (Credit: NASA)

The Babylonians divided the week into seven days, each one in honour of a celestial body within our solar system:

Because of its red appearance in the night sky, many ancient civilizations associated Mars with war. In English, the word "Tuesday" is derived from the Norse god Tyr, who is the equivalent of Mars, the Roman god of war.

Martian exploration

Many missions have been sent to explore Mars, but only 50% have been successful due to the significant challenges caused by the Martian atmosphere. Landing safely on Mars requires a creative combination of heat-shielding, rocket-powered descent, and parachutes.

NASA's Viking 1 and Viking 2 spacecraft were the first to successfully land and explore the surface of Mars in . These spacecraft were designed to search for signs of life on Mars.

One of the greatest successes in planetary exploration was the Opportunity rover, which landed on Mars in . It had a planned mission lifetime of only 90 days but ended up exploring the Martian surface for over 14 years. The rover travelled a record-breaking 45 km of the Martian surface and helped scientists better understand Mars's geology and climate. Opportunity's twin, the Spirit rover, also collected data for over 20 times longer than its planned mission.

NASA's Curiosity rover, which is currently exploring Mars, has travelled over 20 km on the red planet's surface. Curiosity analyzes Martian soil with a Canadian-made geology instrument called APXS, led by Dr. Ralf Gellert (University of Guelph). To date, APXS has sent over 1500 scientific results back to Earth!

The Canadian Space Agency also funds Canadian scientists who are participating in other international Mars missions:

The future of Mars exploration will not only involve robots, but humans as well. With increased crew autonomy, the long-duration missions needed to reach the red planet will soon become reality.

Going to Mars: a complex endeavour

Sending crewed missions to the red planet is a long-term goal of international space agencies. However, a number of important factors must be taken into account when planning a mission:

Mars hoax: Mars will not appear to be the same size as the Moon

For over 15 years, a persistent falsehood has resurfaced on the Internet almost every summer. The rumour alleges that on the night of August 27, Mars will appear to be as large as the full Moon, a once-in-a-lifetime event that will not happen again until the year 2287. This hoax may have arisen in part because Mars appeared to be larger than usual on , when it made its closest approach to Earth in 60,000 years. However, because of the great distance between Earth and Mars, the red planet cannot possibly appear to be as big as the Moon, even when it is magnified by a telescope.

Explore further

Date modified: