Exploring Mars, Past and Present

Young Astronomers Blog, Volume 29, Number 2.

Back in the 19^th century there was a focus on the planet Mars. Italian astronomer Giovanni Schiaparelli studied the surface of Mars during the opposition of 1877 and believed he saw lines crossing the planet. He called them canali, which means channels. The term was later mis-translated as “canals”. The search for Martian “canals” continued with Perceval Lowell who thought they were built by intelligent beings. He published three books, Mars (1895), Mars and Its Canals (1906), and Mars as the Abode of Life (1908), describing what he believed we would find on Mars.

Speculation about life on Mars led to several science fiction works including the 1898 book The War of the Worlds by H. G. Wells. The War of the Worlds was adapted for a Halloween eve radio broadcast by Orson Welles in 1938. The broadcast was so realistic that it created panic over an alleged Martian landing in New Jersey.

However, to really understand Mars, we had to go there.

With the dawn of the space age, NASA implemented the Mariner program. The first two Mariner missions were targeted for Venus. Then, beginning with Mariner 3 and 4, NASA set its sight on Mars. Mariner 3 launched in November 1964 but failed to make it into Earth orbit. Mariner 4 followed soon after and headed off toward Mars. It would give us our first close look at the red planet. Mariner 4 reached Mars in July 1965 and took 21 grainy black and white photographs as it flew by. The images showed a very “moon-like” Martian surface covered with craters. It clearly did not have the canals and life many had hoped for.

After two more Mariner flybys, the next step was to put a spacecraft into Martian orbit with Mariner 8 and 9. Mariner 8 failed to reach Earth orbit. A few days later in May 1971, Mariner 9 began its journey toward Mars. A planet-wide dust storm engulfed the planet as Mariner 9 approached Mars. Mariner had made it all the way to Mars but couldn’t see anything. However, as the storm cleared, photos showed four objects extending up above the dust. Mariner had discovered a range of ancient volcanoes in the Tharsis region, including Olympus Mons, the largest volcano in the Solar System. It also found a huge canyon system extending 2,500 miles across the surface of Mars. It was named Valles Marineris in honor of the Mariner spacecraft. Mariner 9 eventually took over 7,000 photos and mapped 80% of the Martian surface.

After first flying by Mars and then achieving orbit, the next goal was to successfully land on the red planet. This was accomplished with the Viking missions. In 1976, two Viking orbiters, each carrying a lander, reached Mars. The United States completed its first soft landing on another planet when the two Viking landers touched down on the Martian surface. Viking 1 landed on Chryse Planitia in July and Viking 2 on Utopia Planitia in September.

After Mariner and Viking there was a pause for twenty years as Mars faded from NASA’s focus. Beginning in 1996, NASA again turned its attention to the red planet with the launch of the Mars Global Surveyor. This spacecraft orbited Mars from 1997 through November 2006 beginning a long and continuous close-up study of the planet, which continues to this day.

Several additional orbiters followed, including Mars Odyssey (2001) and the Mars Reconnaissance Orbiter (2006), both of which are still in operation today. Two landers, Pathfinder (1997) and the Phoenix Lander (2008), were also sent to Mars to further explore the Martian surface.

Rovers followed beginning with the small Sojourner rover, which traveled along with Pathfinder and explored the area around its landing site. Spirit and Opportunity were next, landing on opposite sides of the planet in early 2004. Spirit landed in the Gusev Crater and Opportunity in the Meridiani Planum. These two rovers far exceeded their initial 90-day missions and explored Mars for years. They both traveled miles across the Martian surface before their missions ended in 2010 (Spirit) and 2019 (Opportunity).

The largest and most sophisticated Martian rover is the Mars Science Laboratory (Curiosity). Curiosity landed in the Gale crater in August 2012 and has been exploring the area around Mount Sharp ever since. You can follow the path of Curiosity online as it moves its way up the lower slopes of the mountain looking for signs of water in Mars’ ancient past.

After the successful landing of Curiosity, NASA sent two additional spacecraft to Mars.

• MAVEN entered orbit in 2014 and is studying the atmosphere of Mars.
• InSight, a fixed lander, touched down in 2018 and is exploring the Martian interior. By early 2020, it had detected almost 500 marsquakes. Just recently, NASA abandoned efforts to drill into the Martian soil with a heat probe, because it wouldn’t go more than a couple of feet into the ground.

As a follow up to Curiosity, NASA launched the Perseverance rover in July 2020. Riding along with Perseverance is the first Martian helicopter, Ingenuity. The rover will be carrying several instruments including a Martian weather station.

Landing on Mars is no easy task. In 2012, NASA described Curiosity’s landing as the “seven minutes of terror.” Perseverance will go through the same process. It must go from over ten thousand miles per hour to zero in seven minutes using a heat shield, a parachute, rockets, a sky crane, and then rockets again. It must do it all without any communication from the Earth. In mid-February 2021, Perseverance successfully landed in the Jezero crater.

Two other spacecraft, UAE’s Hope and China’s Tianwen-1, are now in orbit about Mars after also arriving in February 2021. China’s mission includes a lander and rover, although touchdown is not scheduled until later in 2021.

For more on Mars and the Perseverance Rover launch, see Journey to a Red Planet.

For some discussion on the possibility of life in our solar system, including Mars, see Water, Phosphine, and the possibility of life elsewhere in the Solar System.