The Martian Radiation Experiment, or MARIE was designed to measure the radiation environment of

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmos ...

using an energetic particle

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

as part of the science mission of the

2001 Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectr ...

spacecraft (launched on April 7, 2001). It was led by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...

Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight control are conducted. It was renamed in honor of the late ...

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.Francis A. Cucinotta
''Martian Radiation Environment Experiment – MARIE''
NASA: JSC, last update October 27, 2003. (archive) Since

space radiation Health threats from cosmic rays are the dangers posed by cosmic rays to astronauts on interplanetary missions or any missions that venture through the Van-Allen Belts or outside the Earth's magnetosphere. They are one of the greatest barriers ...

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 through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, vi ...

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 human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...

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

cosmic rays Cosmic rays 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 System in our ow ...

emitted by our local star, the Sun, and from stars beyond the

Solar System The Solar System Capitalization 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 "Solar ...

as well. Space radiation can trigger

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bl ...

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 and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

. Similar instruments are flown on the

Space Shuttle The Space Shuttle is a retired, partially 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. Its official program na ...

s and on the

International Space Station The International Space Station (ISS) is the largest Modular design, modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos ( ...

(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. In the autumn of 2003 after a series of particularly strong

solar flare A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other sola ...

s MARIE started malfunctioning, probably as a result of being exposed to the solar flare's intense blast of particle radiation. The instrument was never restored to working order.

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 ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectr ...

's cruise from Earth to Mars. It stored large amounts of data for

downlink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...

, 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 The gray (symbol: Gy) is the unit of ionizing radiation dose in the International System of Units (SI), defined as the absorption of one joule of radiation energy per kilogram of matter. It is used as a unit of the radiation quantity absorbed do ...

/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