What It Actually Takes to Land on Mars?

Mars has just enough atmosphere to cause problems and not nearly enough to solve them. That single fact explains why landing there remains one of the hardest things anyone has attempted, and why the failure rate is far higher than for any other destination we've visited repeatedly.

The atmosphere problem

Landing on the Moon is a pure rocketry problem — no air, so you slow down entirely by burning fuel. Landing on Earth is a pure aerodynamics problem — thick air, so a heat shield and parachutes do nearly all the work.

Mars is neither. The atmosphere is about one percent as dense as Earth's at sea level. That's thick enough to generate serious heating on arrival, so you need a heat shield. But it's far too thin for parachutes alone to slow a heavy spacecraft to a survivable speed. You need everything: heat shield, parachute, and rockets, in sequence, in the right order, with no margin.

Seven minutes alone

The descent takes around seven minutes. A radio signal takes somewhere between four and twenty-four minutes to reach Mars depending on where the planets are in their orbits.

By the time mission control sees that the spacecraft has entered the atmosphere, the landing has already succeeded or failed. Every decision — when to release the parachute, when to cut it away, when to fire the engines, whether the ground below is safe — is made by software, alone, with no possibility of intervention.

Why each attempt looks different

There's no standard Mars landing system, because the right approach depends heavily on mass. Airbags worked for the small early rovers, which simply bounced across the surface until they stopped. Heavier payloads need powered descent, and the heaviest have required a sky crane — a rocket-powered stage that hovers and lowers the rover on cables before flying away to crash at a safe distance.

Each of these looks absurd on paper. Each was chosen because the alternatives were worse.