And that’s why engineers have repeatedly come up with ingenious tactics for touching down on Mars. No one, or even two, solutions can accomplish the job.
The Viking landers used both parachutes and descent rockets to slow the spacecraft down just before landing, then the lander’s legs served as shock absorbers. Plus, Viking's mission planners had to design special “showerhead” style rockets to avoid cooking the dirt beneath the spacecraft, which would have killed any potential signs of life they were looking for.
But when NASA started sending rovers to Mars, it quickly realized Viking's tactics wouldn’t work. If the retro rockets fired too close to Mars’ dusty surface, they could fling rocks and debris back onto a delicate rover’s instruments and solar panels, putting it in danger.
That's why NASA wrapped the Mars Exploration Rovers — Spirit and Opportunity — in airbags. Those airbags let the rovers safely bounce along Mars’ surface until they shed their final bit of momentum. Like the Skycrane maneuver, this bold idea was sound in theory, but seemed crazy at the time.
And in the years before the Mars Exploration Rovers were set to arrive at the Red Planet, the world’s space agencies got a series of painful reminders on the perils of interplanetary space travel. (Read more: The ‘Mars Underground’: How a Rag-Tag Group of Students Helped Spark a Return to the Red Planet.) Russia, Japan, The European Space Agency and the United Kingdom all saw missions fail at Mars. And NASA itself suffered back-to-back high-profile failures at Mars to round out the 1990s: the Mars Climate Orbiter burned up on entry and the Mars Polar Lander was destroyed during its landing.
At the turn of the millennium, NASA was keen on getting a win. And in 2003, its engineers delivered two successful landings — the Spirit and Opportunity rovers — using the audacious airbag system.
“We stuck two landings on the Mars Exploration Rovers, and when we got done with that we were pretty arrogant kids,” Steltzner recalls. With those successes in the bag, Steltzner and the other NASA engineers working on entry, descent and landing were riding high.