The Mars Radiation Environment Experiment (MARIE) was designed to measure the radiation environment of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

using an energetic particle

spectrometer A spectrometer () is a scientific instrument used to separate and measure Spectrum, spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomeno ...

as part of the science mission of the 2001 Mars Odyssey spacecraft (launched on April 7, 2001). It was led by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...

and the science investigation was designed to characterize aspects of the radiation environment both on the way to Mars and while it was in the Martian orbit. Since

space radiation Space is a three-dimensional continuum containing positions and directions. In classical physics, physical space is often conceived in three linear dimensions. Modern physicists usually consider it, with time, to be part of a boundless ...

presents an extreme hazard to crews of interplanetary missions the experiment was an attempt to predict anticipated

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

doses that would be experienced by future

astronaut An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a List of human spaceflight programs, human spaceflight program to serve as a commander or crew member of a spa ...

s and it helped determine possible effects of Martian radiation on human beings. Space radiation comes from

cosmic rays Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar ...

emitted by Earth's local star, the Sun, and from stars beyond the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

as well. Space radiation can trigger

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

and cause damage to the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

. Similar instruments are flown on the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

s and on the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

(ISS), but none have ever flown outside Earth's protective

magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...

, which blocks much of this radiation from reaching the surface of our planet. MARIE was turned off on 28 October 2003 after communication was lost during a large solar proton event.

Operation

A spectrometer inside the instrument measured the energy from two sources of space radiation: galactic cosmic rays (GCR) and solar energetic particles (SEP). As the spacecraft orbited the red planet, the spectrometer swept through the sky and measured the radiation field. The instrument, with a 68-degree field of view, was designed to collect data continuously during Mars Odyssey's cruise from Earth to Mars. It stored large amounts of data for downlink, and operated throughout the entire science mission.

MARIE specifications

The Martian Radiation Environment Experiment weighs 3.3 kilograms (7.3 pounds) and uses 7 watts of power. It measures 29.4 x 23.2 x 10.8 centimeters (11.6 x 9.1 x 4.3 inches).

Results

The diagram above indicates that a main radiation exposure is about 20 mrad/d resulting in annual dose of about 73 mGy/a. However occasional solar proton events (SPEs) produce a hundred and more times higher doses (see the diagram above). SPEs, which were observed by MARIE, were not observed by sensors near Earth confirming that SPEs are directional. Thus the average in-orbit doses were about 400–500mSv/a. JPL reported that MARIE-measured radiation levels were two to three times greater than that at the

(which is 100–200 mSv/a).{{cite web, title=Radiation Dose-Equivalent: International Space Station Compared to Mars Orbit, url=http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA03745, publisher=JPL, access-date=30 September 2012, date=2002-12-07 The levels at the Martian surface might be closer to the level at the ISS due to atmospheric shielding – ignoring the effect of thermal neutrons induced by GCR.

References

External links

NASA's site on MARIE
2001 Mars Odyssey Spacecraft instruments Missions to Mars Cosmic rays