Spacecraft land on Mars by entering the planet’s atmosphere at high speed, shedding energy through friction with the atmosphere, and using a combination of heat shields, parachutes, and braking systems to slow down before reaching the surface. The exact method depends on the spacecraft’s size, its landing site, and the scientific work it is designed to perform.
Landing is one of the most difficult parts of a Mars mission. A spacecraft must reduce its speed from thousands of miles per hour to nearly zero in just a few minutes, navigate toward a suitable landing area, and survive the intense heating and forces of atmospheric entry. It must do all this largely on its own because signals between Earth and Mars take several minutes to travel in either direction.
Engineers call this sequence entry, descent, and landing, or EDL. Each stage solves a different problem: entering the atmosphere safely, slowing down enough to descend, and reaching the surface without destroying the spacecraft.
Why landing on Mars is so difficult
Mars presents a challenging combination of conditions. Its atmosphere is thick enough to generate substantial heat and drag around an incoming spacecraft, but too thin to slow a heavy lander as effectively as Earth’s atmosphere can.
Mars has only about 38 percent of Earth’s surface gravity, which helps somewhat, but its atmosphere is less than 1 percent as dense as Earth’s at the surface. A parachute that works well on Earth therefore produces much less drag on Mars, especially for a large spacecraft.
The planet’s atmosphere also creates intense heat during entry. Although it is thin, a spacecraft arriving at interplanetary speeds compresses the gas in front of it, producing a layer of extremely hot gas. Without thermal protection, this heat could destroy the vehicle before it reaches the ground.
Engineers must also account for the planet’s terrain. Mars has enormous volcanoes, deep canyons, rocky plains, and dusty landscapes. A spacecraft must avoid dangerous slopes, large rocks, and other obstacles while reaching a location suitable for its scientific mission.
These challenges leave little room for error. A lander that reaches the ground too quickly can be destroyed on impact, while one that slows down too early may run out of propellant or drift away from its intended landing area. The landing system must coordinate several technologies in a carefully timed sequence.
How a spacecraft enters the Martian atmosphere
The landing process begins long before the spacecraft reaches the ground. After traveling from Earth, the vehicle approaches Mars on a trajectory calculated to intersect the planet’s atmosphere at the correct angle.
Many Mars landers use a protective aeroshell, a structure that surrounds the lander during entry. It typically consists of a heat shield at the front and a backshell behind it. Together, these components protect the spacecraft from heating and help control its movement through the atmosphere.
When the vehicle encounters the upper atmosphere, it is traveling at several miles per second. The air ahead of it becomes compressed and heated, creating an intense thermal environment. The heat shield absorbs and manages this energy, often through ablative materials that gradually char, decompose, or erode, carrying heat away from the spacecraft.
At the same time, atmospheric drag reduces the vehicle’s speed. Drag is the force that opposes an object moving through a fluid, including air. The aeroshell’s broad shape increases this resistance, allowing the atmosphere to remove a substantial amount of the spacecraft’s kinetic energy.
This process is called aerobraking during entry in a general physical sense, although aerobraking has a more specific meaning in spacecraft operations: using repeated atmospheric passes to change an orbit. During landing, the more precise terms are atmospheric entry and aerodynamic deceleration.
The heat shield and aeroshell are essential because they allow the atmosphere to do much of the work of slowing the spacecraft without requiring the vehicle to carry enough fuel to brake entirely with rockets.
However, atmospheric entry does not bring a spacecraft to a safe landing speed by itself. Even after losing much of its initial velocity, the vehicle is still moving too quickly to touch down safely. The next stages must reduce its speed further.
How parachutes slow a Mars lander
Once the spacecraft has slowed sufficiently and reached a suitable point in the atmosphere, it can deploy a parachute. The parachute creates a large amount of aerodynamic drag, helping reduce the vehicle’s downward speed.
Mars landers commonly use large supersonic parachutes, designed to deploy while the spacecraft is still moving faster than the speed of sound. Deploying a parachute under these conditions is a major engineering challenge because the canopy and suspension lines must withstand powerful forces as they inflate.
A parachute does not eliminate the need for other braking systems. Mars’s thin atmosphere limits the amount of drag it can generate, particularly for heavy vehicles. Even a large parachute cannot slow a massive lander enough to guarantee a gentle touchdown.
For that reason, the parachute is one part of a larger landing system. It reduces the spacecraft’s speed and helps prepare it for the final descent, when the lander must rely on additional equipment to reach the surface safely.
The timing of parachute deployment is critical. If it opens too early or too late, the spacecraft may not have enough time or atmospheric distance to complete the remaining descent. The landing system must determine when conditions are suitable using onboard sensors and preprogrammed logic.
How rockets bring the spacecraft to the surface
After atmospheric drag and the parachute have removed much of the spacecraft’s speed, a powered descent system may take over. Rocket engines provide thrust in the direction needed to oppose the spacecraft’s downward motion and control its final approach.
During powered descent, the spacecraft uses onboard measurements to estimate its position, altitude, and velocity. Its guidance system determines how to adjust the trajectory, while its control system commands the engines to produce the required thrust.
The engines must do more than stop the fall. They may also need to steer the vehicle toward a safer landing area, compensate for variations in the atmosphere, and control the spacecraft’s orientation. Because the vehicle cannot wait for instructions from Earth, these decisions must be made automatically.
Different Mars missions have used different landing arrangements.
NASA’s Viking landers used parachutes and retrorockets to slow their descent before landing on three-legged supports. The Phoenix lander and the InSight lander also used parachutes followed by rocket-powered descent.
NASA’s Curiosity and Perseverance rovers required a more elaborate system because they are large, heavy vehicles that must be placed on the surface without damaging their wheels, instruments, or scientific equipment.
For these rovers, engineers developed a system known as the sky crane. Rather than lowering the rover inside a conventional lander that remains on the ground, the sky crane suspends the rover beneath a rocket-powered descent stage.
How the sky crane lands a rover
The sky crane was used for NASA’s Curiosity rover, which landed in 2012, and Perseverance, which landed in 2021. It allows a large rover to reach the surface without needing to drive down a ramp or roll off a platform.
The sequence begins with the spacecraft entering the atmosphere inside its aeroshell. After atmospheric deceleration, a supersonic parachute deploys to slow the vehicle further. When the spacecraft reaches the appropriate point in its descent, it releases its heat shield so that radar and other onboard systems can assess the remaining distance to the surface.
The parachute eventually separates, and the rocket-powered descent stage ignites its engines. These engines slow the vehicle and guide it toward the landing site. The rover, still folded into its landing configuration, hangs beneath the descent stage on a set of cables.
As the descent stage approaches the ground, it lowers the rover on those cables. The rover’s wheels and suspension are positioned to make contact with the Martian surface while the engines continue to control the descent.
Once the rover detects that it has landed, it sends a signal to the descent stage to cut the cables. The descent stage then flies away from the rover and crashes at a safe distance.
This separation is important. A rocket-powered platform cannot simply shut down and remain directly above a rover without risking damage from exhaust, debris, or a collision. Flying away leaves the rover on the surface with its wheels in contact with the ground and its scientific equipment protected.
The sky crane solves a problem that conventional landing platforms face: a large rover needs to be placed gently on the ground, but the platform itself must also be kept from obstructing the rover’s mobility. Suspending the rover allows it to land directly on its wheels and begin exploring without a separate deployment ramp.
Why Mars landings must happen autonomously
Mars is so far from Earth that radio communication cannot support real-time piloting during the final descent. A radio signal takes several minutes to travel between the planets, and the delay varies with their positions in their orbits.
The entire entry, descent, and landing sequence unfolds too quickly for engineers on Earth to watch the spacecraft’s progress and correct every maneuver. By the time a command sent from Earth arrived, the spacecraft might already have reached the surface.
Instead, the spacecraft follows a carefully designed sequence controlled by onboard computers. Sensors measure conditions such as acceleration, altitude, and motion. Radar can help determine the spacecraft’s height above the ground and its speed relative to the surface. Navigation systems use this information to estimate where the vehicle is and how it is moving.
The guidance software compares these measurements with the desired trajectory and calculates adjustments. The control system then changes the spacecraft’s orientation or engine thrust to keep the descent within safe limits.
Autonomy also matters because conditions cannot be predicted perfectly. Atmospheric density varies, winds can affect the trajectory, and the spacecraft may encounter small differences between its actual motion and the expected path. A robust landing system must respond to these variations without waiting for human intervention.
Some newer landing technologies also assess the terrain during descent. Terrain-relative navigation, for example, compares images of the surface with onboard maps to estimate the spacecraft’s location. This can help a lander avoid hazardous areas and reach a more suitable landing site, provided its sensors and software can identify the terrain reliably.
How engineers choose a landing site
A successful landing depends on more than reaching the ground intact. The spacecraft must also arrive somewhere that supports its scientific goals.
Engineers evaluate potential landing sites using orbital images, elevation data, information about surface materials, and measurements of local conditions. A site may be scientifically valuable because it contains evidence of ancient water, sedimentary rocks, or other features that could reveal Mars’s geological history. But the same location may be difficult to reach safely.
Landing sites therefore involve trade-offs. Relatively flat terrain reduces the risk of a dangerous touchdown, while certain geological features may offer more valuable scientific opportunities. Engineers also consider elevation, because a site at a higher elevation has less atmosphere above it to help slow an incoming spacecraft.
For a rover, the terrain beyond the landing zone matters as well. The mission team needs to know whether the vehicle can travel across the surface, reach its intended targets, and operate within its energy and communications limits.
Landing accuracy has improved through better navigation, surface mapping, and autonomous guidance. Even so, the spacecraft cannot always land at the exact point scientists would choose. Safety constraints and the capabilities of the landing system determine which areas are reachable.
What happens after touchdown
Reaching the surface is not the end of the landing process. The spacecraft must confirm that it has stopped moving, establish communication with Earth, and begin operating in an unfamiliar environment.
A lander may deploy instruments, extend a robotic arm, or begin measuring atmospheric and surface conditions. A rover must check its systems, deploy or position its equipment, and prepare to drive. These activities may occur in stages because engineers need to verify that the spacecraft survived landing and that its mechanisms are functioning correctly.
The Martian environment presents continuing challenges. Temperatures can be very low, dust can accumulate on exposed surfaces, and the thin atmosphere provides little protection against some forms of radiation. A mission’s power system, thermal controls, and communications equipment must all operate within these constraints.
The first data sent back after landing can be especially valuable. Images and engineering measurements help mission controllers determine the spacecraft’s condition, confirm its location, and assess the surrounding terrain. Only after these checks can the mission proceed with confidence to its primary scientific work.
Why every Mars landing is an engineering compromise
No single landing method is ideal for every spacecraft. A small stationary lander, a heavy rover, and a future crewed vehicle would have different requirements for heat protection, parachutes, propulsion, and surface operations.
The atmosphere provides useful braking, but it also generates dangerous heating and cannot stop a heavy vehicle on its own. Parachutes offer substantial drag, but their effectiveness is limited by the thin air. Rockets provide precise control, but they require propellant and add mass to the spacecraft. Autonomous navigation improves landing accuracy, but it depends on reliable sensors, software, and a well-understood operating environment.
Successful Mars landings combine these methods so that each compensates for the limitations of the others. The atmosphere removes much of the spacecraft’s initial energy, parachutes reduce its speed further, and rockets or other terminal landing systems control the final approach. Onboard computers coordinate the sequence because the spacecraft must act faster than Earth-based controllers can respond.
The result is a landing system that transforms an interplanetary spacecraft moving at several miles per second into a functioning scientific vehicle on another world—all within a few minutes of its first encounter with the Martian atmosphere.