The technology of the rover and its landing system is designed to demonstrate substantial new 

capabilities and operational techniques that would 

benefit future NASA missions, from precision landing in a small target zone to extended surface lifetimes to the transmission of extremely large data 

volumes back to Earth.

Scheduled for launch on an Atlas V rocket, Curiosity will derive its electrical power from a MultiMission Radioisotope Thermoelectric Generator 

(MMRTG). Similar to the radioisotope power 

systems used to safely and successfully power 

numerous solar system exploration missions from 

Voyager to Pluto/New Horizons for more than 40 

years, the MMRTG will significantly enhance the 

range and lifetime of the rover. It will also promote 

greater operability of the rover’s science experiAs with any NASA mission that relies on a radioisotope power system, the Mars Science Laboratory has undergone a comprehensive multi-agency environmental review, including public meetings 

and open comment periods, as part of NASA’s 

compliance with the National Environmental Policy 

Act. Additionally, the mission will not launch until 

formal approval is received from the Office of the 

President.

Like previous generations of this type of electricalpower generator, the MMRTG is built with several 

layers of protective material designed to contain 

its plutonium dioxide fuel in a wide range of potential accidents, verified through impact testing. 

Each MMRTG carries eight individually shielded 

general purpose heat source modules (compared 

to 18 modules in the previous generation). The 

thickness of the protective graphite material in the 

center of the modules and between the shells of 

each module in the MMRTG has been increased 

by 20 percent over previous modules. 

ments, which include the first-ever plans to drill 

into Martian rocks for powdered samples to analyze on-site. The MMRTG contains 10.6 pounds 

(4.8 kilograms) of plutonium dioxide as the source 

of the steady supply of heat used to produce the 

onboard electricity and to warm the rover’s systems during the frigid Martian night. 

Mars Science Laboratory

Launch Nuclear Safety

National Aeronautics and Space Administration

In late 2011, NASA plans to launch the largest, 

most capable rover ever sent to another planet. 

The Mars Science Laboratory is designed to enable scientists to determine whether past or present environmental conditions at a selected area 

on the Red Planet could support microbial life 

and its preservation in the rock record. 

Outfitted with six wheels and a sophisticated 

suite of scientific equipment that includes a large 

robot arm, a laser, a weather station, and a drill, 

the Mars Science Laboratory’s jeep-sized rover is 

named Curiosity.

Artist’s concept of Curiosity on Mars

Full-scale cutaway 

models of an MMRTG 

and one of its heat 

source modules, which 

produce electricity 

passively using 

thermocouples with 

no moving parts. (The 

MMRTG is 26 inches 

[67 centimeters] tall.)
JPL 400-1430 03/11 NASA Facts

National Aeronautics and Space Administration

Jet Propulsion Laboratory

California Institute of Technology

Pasadena, California

www.nasa.gov

Extensive technical analysis of the planned launch of the 

Mars Science Laboratory, including review of all similar past 

expendable rocket launches, has been conducted by NASA, 

the U.S. Department of Energy (which provides the MMRTG), 

and external experts. This work has determined that the 

chances of any launch accident are small (3.3 percent), and 

the chances of an accident of the type that would release 

plutonium are about ten times smaller.

In the event of a launch accident, it is unlikely that any plutonium would be released or that anyone would be exposed 

to nuclear material. The type of plutonium used in a radioisotope power system is different from the material used in 

weapons, and cannot explode like a bomb. It is manufactured in a ceramic form that does not become a significant 

health hazard unless it becomes broken into very fine pieces 

or vaporized and then inhaled or swallowed. Those people 

who might be exposed in a Mars Science Laboratory launch 

accident would receive an average dose of 5-10 millirem, 

equal to about a week of background radiation. The average 

American receives 360 millirem of radiation each year from 

natural sources, such as radon and cosmic rays. 

Key Facts: Mars Science Laboratory

Launch Period: November 25 – December 18, 2011

Mass of Rover: 1,950 pounds (890 kilograms)

Launch Vehicle: 

Atlas V 541 from Cape Canaveral Air Force Station, FL

Arrival at Mars: August 6-20, 2012

Website for more information: mars.jpl.nasa.gov/msl

More information on radioisotope space power systems: 

www.ne.doe.gov/space/neSpace2d.html

Follow Mars Science Laboratory on Twitter and Facebook: 

twitter.com/MarsCuriosity

www.facebook.com/MarsCuriosity

For further information, contact:

David Lavery

Science Mission Directorate

NASA Headquarters

Washington, DC 20546

(202) 358-4684

david.lavery@hq.nasa.gov

Each MMRTG heat source module includes several layers of protective material

NASA, several other federal agencies, the State of Florida and 

the local governments surrounding Kennedy Space Center 

are preparing in advance to respond to any launch accident 

through specific communication procedures, the use of advanced environmental sensors around the launch area, rehearsal of coordinated response to various launch scenarios, 

and informational briefings to local communities and emergency responders. In the case of a launch accident, related 

alerts could include precautionary measures such as directions for people to stay indoors for a limited duration.

NASA and the Department of Energy are committed to continuing their long heritage of safe and careful use of radioisotope power systems in service of the peaceful exploration 

of space for the benefit of all humankind. This commitment 

includes providing easily accessible and widely broadcast updates during the launch activity for Curiosity. The information 

campaign will include ongoing updates to TV, radio and online 

media outlets, and active use of social media, in order to provide timely and complete information to the public.

Aeroshell

Cap

GIS

GIS Cap

Fueled

Clad

Floating

Membrane Fuel

Pellet Graphite Impact

Shell (GIS)

CBCF

Disk

Carbon Bonded

Carbon Fiber

(CBCF) Sleeve

CBCF

Disk

Aeroshell

Lock Screw

Individual

GPHS Module

Probability 

of an Accident 

with No Release

2.9%

Probability 

of a Launch Area 

Accident with 

Release

0.2%

Probability of an Accident

Outside the Launch Area with Release

0.2%

A comparison of potential radiation exposures (calculated using effective whole-body 

dose in millirem). Source: Health Physics Society

Probability of a 

Successful Launch 

(Earth Escape)

96.7%

350

400

U.S. Population 

Background Radiation

(Annual Average)

Airline Flight 

Attendant

(Annual Average 

Work Exposure) Mammogram

(Four Views)

Dental X-ray

(Panoramic)

Average 

Individual

Exposure 

from MSL 

Accident with

Release

50

100

150 200 250 300

millirem

0

350

400

450

500