Solar panels do work on Mars, and they’ve been powering spacecraft there for over two decades. But they produce significantly less electricity than they would on Earth, and dust is a constant threat that has ended missions. Mars receives only about 43% of the sunlight Earth gets, and that number drops further during the planet’s notorious dust storms. Several NASA landers and rovers have run successfully on solar power, but the agency now favors nuclear power for its most ambitious Mars missions.
How Much Sunlight Reaches Mars
Mars orbits about 1.5 times farther from the Sun than Earth does. Because sunlight intensity drops with the square of distance, the Martian surface receives roughly 590 watts per square meter at its brightest, compared to about 1,370 watts per square meter at the top of Earth’s atmosphere. That alone cuts available solar energy by more than half.
The Martian atmosphere adds another layer of loss. While it’s far thinner than Earth’s, it’s loaded with fine dust particles that scatter and absorb sunlight. On a clear day, enough light gets through to generate useful power. During a regional or global dust storm, the sky can darken so severely that NASA’s Spirit rover once produced only 89 watt-hours in a single Martian day, far less than it needed to function. These storms can last weeks or even months, and there’s no way to predict exactly when they’ll hit.
The Cold Actually Helps (to a Point)
One advantage Mars does offer is cold temperatures. Solar cells become more efficient as they cool down, which is why panels on Earth perform slightly better in winter than in summer. On Mars, surface temperatures range from about negative 113°C to negative 23°C depending on location, season, and time of day. Research from the American Institute of Aeronautics and Astronautics found that photovoltaic cells hit peak efficiency at roughly negative 73°C to negative 123°C, which lines up well with typical Martian conditions. Below that range, efficiency actually starts to decline again, so the coldest Martian nights don’t provide unlimited benefit. Still, the temperature boost partially offsets the weaker sunlight.
Dust: The Real Problem
Dust is the single biggest challenge for solar power on Mars. It affects panels in two ways: it accumulates directly on the glass surface, and it hangs in the atmosphere blocking sunlight before it ever reaches the panels.
Data from the Mars Pathfinder mission measured dust accumulation causing about 0.3% power loss per sol (one Martian day). That sounds small, but it compounds. Over weeks and months, a thick film builds up that significantly reduces output. Researchers found that the rate of loss follows a curve rather than a straight line, because some natural dust removal occurs from wind. The mathematical model fit to real Mars data shows power loss proportional to the fourth root of time, meaning the degradation is steepest in the early days and gradually slows as deposition and removal reach a rough balance.
But natural cleaning is unreliable. The Spirit and Opportunity rovers occasionally benefited from gusts and dust devils that swept their panels partially clean, giving them sudden power boosts. Opportunity survived for nearly 15 years partly thanks to these lucky cleaning events. InSight, which landed in 2018, wasn’t so fortunate. Dust steadily accumulated on its panels, and the lander had no effective way to remove it.
Why Cleaning Panels Is So Difficult
You might assume engineers would just add wipers or fans to keep panels clean. NASA considered this but concluded that brushes or fans would add weight and create new failure points on the spacecraft. Mechanical systems that work fine on Earth face serious challenges in Martian dust, cold, and thin atmosphere.
The InSight team got creative. They tried pulsing the solar panel deployment motors to shake dust loose, but it didn’t work. They eventually tried a counterintuitive technique: using the lander’s robotic arm to trickle sand near the panels. The idea was that larger sand grains would bounce off the panel surface and carry smaller dust particles away in the wind. This actually produced a measurable power boost, but it was a temporary fix, not a long-term solution.
Some people even suggested flying the Ingenuity helicopter over to blow InSight’s panels clean. Beyond being too risky, Ingenuity was about 3,450 kilometers away at the time. The episode highlights just how few options exist once dust starts building up.
How NASA’s Mars Missions Have Used Solar Power
Several successful Mars missions ran on solar panels. The Spirit and Opportunity rovers, which landed in 2004, relied entirely on solar arrays. Spirit operated for about six years before a dust storm and mechanical issues ended its mission. Opportunity lasted until 2018, when a global dust storm finally starved it of power after nearly 15 years of operation.
The Phoenix lander (2008) and InSight lander (2018) also used solar power. InSight completed all its primary science objectives before dust accumulation gradually reduced its power budget. A regional dust storm in January 2022 forced it into safe mode, and while it recovered enough to continue limited operations, the team spent its final months carefully rationing power by running instruments for short periods. The mission ended in December 2022.
NASA has also invested in optimizing solar cells specifically for Mars. A program called MOST (Mars Optimized Solar Cell Technology) launched in 2004 to modify standard space-grade solar cells for the Martian light spectrum, which differs from what panels encounter in Earth orbit. Standard cells lose some performance under Mars conditions, and the program aimed to close that gap.
Why NASA Now Prefers Nuclear Power
For its most capable Mars missions, NASA has shifted toward nuclear power. The Curiosity rover (2012) and Perseverance rover (2020) both use radioisotope power systems that convert heat from decaying plutonium into electricity. These systems produce a few hundred watts continuously, day and night, regardless of dust or storms.
A NASA decision document comparing the two technologies laid out the reasoning clearly. Nuclear fission systems are more robust and better suited to Mars because they provide consistent power across a wide range of landing sites, work around the clock, and keep running during global dust storms. Solar power has a lower per-unit cost, but it requires massive battery banks to store energy for nighttime use, and those batteries need to charge during the day while simultaneously powering the spacecraft. That dual demand strains the system.
The document also noted a fundamental limitation that no engineering fix can solve: even if you could keep panels perfectly clean, suspended dust in the atmosphere during a major storm still blocks sunlight. You can’t clean the sky. For a crewed Mars mission where power failure could be fatal, that risk was unacceptable, and NASA selected nuclear fission as the baseline power technology.
Could Solar Still Play a Role
Solar panels remain a viable option for smaller, shorter, or lower-power Mars missions, especially those that land near the equator where sunlight is strongest. They’re lighter, cheaper, and simpler than nuclear systems. If a mission can tolerate some downtime during dust storms and doesn’t need power through the long Martian night, solar works.
For larger operations, solar could serve as a supplementary power source alongside a nuclear primary system. A human base, for example, might use solar arrays to reduce the load on its reactor during clear seasons while relying on nuclear power as the backbone. The combination would provide redundancy without the single-point-of-failure risk that comes with solar alone. The panels would still degrade from dust and still go dark during storms, but with nuclear backup, that becomes an inconvenience rather than a crisis.