After the Moon, Mars is the next destination for space exploration. Humans have actually been sending probes to Mars for more than 50 years
In recent years, work has begun on ways that humans could be sent to the Red Planet, examining how they would survive the trip and what they would do once there. First, however, there is much that still needs to be learned about our neighbor.
Mars exploration began in the 1960s with flybys. Early attempts by the US and USSR failed, but in July 1969 Mariner 6 was the first US probe to reach Mars - ten days after man landed on the Moon.
It wasn’t until the 1990s that the first rover was sent there. Unlike stationary landers, rovers are, as their name suggests, mobile. That greatly broadens the scope of possible exploration. Such an advance in technology was not possible without challenges. The main one was finding a way to land safely on the planet’s surface, but another was about power.
Saft’s first collaboration on Mars missions was with Pathfinder, which landed on July 4, 1997, using a parachute and a system of giant airbags to ensure it arrived undamaged. The lander was powered by primary lithium sulfur dioxide (Li-SO2) cells manufactured at Saft’s Cockeysville facility – and its rover, Sojourner, was the first on the Martian surface.
Outfitted with instruments to analyze the planet’s atmosphere, climate and geology, Sojourner and Pathfinder delivered a lot of data and helped to develop exploration techniques that were used on later missions.
Six years after the end of the Pathfinder mission, NASA launched two new rovers destined for Mars: Spirit and Opportunity. Though the rovers did not use Saft batteries, each was carried by a lander that relied on Saft Li-SO2 batteries for the critical entry, descent and landing phases. After entering the planet’s atmosphere, the batteries provided the power to slow the lander from 12,000mph to 1,000mph over four minutes, deploy a parachute to further slow the craft to 200mph and then fire retro-rockets and deploy airbags.
The lander hit the surface of Mars at 30mph, bouncing several times, but remaining well protected thanks to its airbags. Spirit and Opportunity both landed in January 2004, on opposite sides of the planet, and rolled out over Martian soil. The twin rovers were more mobile than their predecessor and it is due to them that we discovered the first evidence of water.
Both rovers remained operational for longer than planned and Opportunity is still working today; in 2015, it broke the record for the longest off-Earth roving distance. By 2017, the rover had travelled 28 miles.
Despite this remarkable progress, Martian exploration is still in its infancy – and Saft remains closely involved in ongoing work. Saft batteries will visit the planet again in 2020 as part of the ExoMars mission. The goal of that mission will be to search for evidence of current or extinct life on the red planet. While nobody expects to be met with the little green men of science fiction cliché, scientists hope to find some sign of bacterial cultures.
For that reason, everything constructed for the mission, including the battery, is being made to exceptionally high standards of cleanliness, to avoid contaminating any complex organic molecules that may be discovered.
The battery cells that Saft has developed for the mission are compact and lightweight, so that more of the mission payload can be used for scientific instruments, and are designed to survive extreme temperature fluctuations, from -30°C to +65°C, during the nine-month journey and at least two years on the planet. A mockup of the ExoMars Rover and its battery were displayed at Le Bourget as part of the 2017 Paris Air Show. The launch date for the real thing is fast approaching.