National Aeronautics and Space Administration

stcNASAFa

www.nasa.gov

Mars Exploration

Radioisotope Power and Heating for Mars Surface Exploration

Electrical power is critical for exploring Mars — it 

keeps radios, computers, and scientific instruments 

working on Mars lander and rover missions. Electrical 

power systems must survive Mars’ harsh environment, where temperature extremes, dust storms and 

high radiation levels from space present challenges 

to spacecraft systems that must operate long enough 

for missions to accomplish their scientific goals. 

Currently, two kinds of electrical power systems are 

considered — a combination of solar arrays and batteries, and radioisotope power systems.

Extreme Cold and Dust

For some missions, Mars is close enough to the 

Sun that solar energy is sufficient to power a lander 

or a rover. But surface-based missions that rely exclusively on solar power systems can be short-lived 

due to the harsh Martian environment, especially the 

day-to-night temperature extremes, which can vary 

by more than 150 degrees Fahrenheit. In addition, 

fine dust covers the surface of Mars and is carried by 

winds throughout its atmosphere. This dust can settle 

and build up on solar panels. Ultimately, the dust can 

block sunlight from the solar cells, reducing or cutting 

off power and ending the mission. Batteries on landers and rovers can be recharged while spacecraft solar panels are working, but even the batteries and the 

central electronics must be warmed over the course 

of subzero Martian nights when temperatures can dip 

to –150 degrees Celsius (–238 degrees Fahrenheit). 

Small radioisotope heaters are sometimes used to 

keep the electronics and other equipment within 

range of their operating temperatures.

Science Requirements 

Radioisotope electrical power and heating systems 

enable science missions that require greater longevity, more diverse landing locations or more power 

than missions limited to solar power systems.

With radioisotope power systems, years of operation 

are possible. The Viking landers, each with a radioisotope thermoelectric generator, operated on Mars 

for four and six years, respectively. By comparison, 

the 1997 Mars Pathfinder mission, which used radioisotope heaters but only solar and battery power 

on the rover, lasted only three months. The Mars 

Exploration Rovers, also equipped with radioisotope 

heaters and solar and battery power, have well exceeded their original three-month mission lifetimes, 

but are limited in their operations in winter’s cold and 

dim sunlight.

More Places to Explore, Greater Science Return

Radioisotope power systems do not require any sunlight to operate, permitting spacecraft to land at more 

diverse locations regardless of season, time of day or 

latitude. Because of the number of moving parts, rovers and other mobile explorers require more power 

than landers. If rovers are solar powered, they must 

land and operate within a fairly narrow latitude band 

near the equator where enough sunlight shines to 

provide adequate electricity. For rovers, radioisotope 

electrical power systems could provide the capability 

to land and operate at a greater variety of scientifically important locations. 
NASAFacts

National Aeronautics and Space Administration

Jet Propulsion Laboratory

California Institute of Technology 

Pasadena, California 

4-06

Accessing the Most Promising Sites

As NASA’s rovers have shown, Martian terrain varies dramatically, and features challenges such as 

craters, gullies and fields of rocks and boulders. 

Navigating and driving through complex and rugged terrains also requires more energy than driving 

in barren flatlands. Frequently, the energy required 

to move through very complex, and scientifically 

interesting, areas may exceed the capacity of solarpowered systems. Shadows in rugged terrain such 

as canyons or ridges further limit the effectiveness of 

solar-powered landed spacecraft. Vehicles that draw 

energy from radioisotope power systems would not 

be limited by such conditions.

Understanding the “real” Mars requires global 

accessibility and the ability to reliably traverse 

rugged terrain in all seasons regardless of dust, 

temperature or lack of sunlight. Radioisotope power 

and heating systems for Mars surface missions provide expanded surface access, opening up far more 

terrain for intensive surface-based exploration and 

discoveries.

For More Information 

Contact Dwayne Brown at dwayne.c.brown@nasa.

gov

2