Radiation Assement Detector

About RAD

The RAD instrument

Figure: The RAD Instrument.

The Radiation Assessment Detector (RAD) is an investigation to detect and analyze the most biologically hazardous energetic particle radiation on the Martian surface as part of the Mars Science Laboratory (MSL) mission. It has made the first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars is a key life-limiting factor that directly affects habitability and the ability to sustain life, and poses a challenge for future human explorers on the red planet. Thus, RAD measurements help planning for future human exploration and give us a direct measure of what levels of radiation to expect when we send astronauts to Mars in the future.

The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment.

About MSL

Mars Science Laboratory is the first planetary mission which used precision landing techniques, steering itself towards the Martian surface similar to the way the space shuttle controls its entry through the Earth's upper atmosphere. In this way, the spacecraft flew to a desired location above the surface of Mars before deploying its parachute for the final landing. In the final minutes before touchdown, the spacecraft activated its parachute and retro rocketed before lowering the rover package to the surface on a tether (similar to the way a skycrane helicopter moves a large object). This landing method enabled the rover to land in planned area. On August 6, 2012 MSL reached the Mars surface at the Gale Crater.

Like the Mars Exploration rovers (MER) now on the surface of Mars, Mars Science Laboratory has six wheels and cameras mounted on a mast. It carries a laser for vaporizing a thin layer from the surface of a rock and analyzing the elemental composition of the underlying materials. It is also able to collect rock and soil samples and distribute them to on-board test chambers for chemical analysis. Its design includes a suite of scientific instruments for identifying organic compounds such as proteins, amino acids, and other acids and bases that attach themselves to carbon backbones and are essential to life as we know it. It can also identify features such as atmospheric gases that may be associated with biological activity. And of course, it measures the radiation environment on the surface of Mars to assess the affect of radiation on habitability as well as aid planning for future human exploration, as discussed above.

                      Curiosity at JPL.

Figure: Curiosity at JPL.

NASA selected a landing site on the basis of highly detailed images sent to Earth by the Mars Reconnaissance Orbiter, in addition to data from earlier missions. The rover carries a radioisotope power system that generates electricity from the heat of plutonium's radioactive decay. This power source gives the mission an operating lifespan on Mars' surface of a full martian year (687 Earth days) or more while also providing significantly greater mobility and operational flexibility, enhanced science payload capability, and exploration of a much larger range of latitudes and altitudes than was possible on previous missions to Mars.

                          Location of Curiosity relative to other Mars missions.

Figure: Location of Curiosity relative to other Mars missions.

As already mentioned Curiosity has landed in a flat region of Gale crater which is situated on the rim of the Southern highlands. In its center Gale crater contains a large mound which is layered. These layers (stratigraphy) appear to have been deposited sequentially, possibly as sediments. The lowest layers contain minerals which on Earth are only known to form in the presence of liquid water. As one proceeds higher up through these layers, their origin appears to be drier and drier. Thus Gale crater offers a chronology of Mars which only needs to be read by MSL. It dates from early (Noachian) possibly wet Mars through middle-age (Hesperian) to modern (Amazonian) Mars. It may contain the key to understanding what went wrong in the history of Mars, why Mars is today so dry. Do the 'wet' deposits contain signs of life on Mars in the distant past? Are there other signs of life, possibly even in more recent deposits? MSL will be able to answer these questions.