Historic Spacecraft - Mars Probes Historic Spacecraft Historical Overview of Mars Exploration Since the early 1960's, dozens of spacecraft have been sent to explore Mars. The first spacecraft to successfully flyby Mars was the American Mariner 4 spacecraft. Orbit was first achieved with Mariner 9 in 1971. The mission returned thousands of images, giving us our first global look at the planet. The Soviet Mars 3 mission was the first to land on the surface. Unfortunately, communication ceased shortly after touchdown. The Viking program consisted of two orbiters and two landers. The landers studied many aspects of the surface and conducted sophisticated experiments to search for life. Mars missions have seen frequent failures, but have also some spectacular successes. 1996 saw the launch of Mars Pathfinder and Mars Global Surveyor . The Pathfinder lander tested an airbag landing technique and included the small Sojourner rover. Mars 96 , a Russian probe launched the same year, suffered a booster malfunction and fell back to Earth. The success of both Mars Pathfinder and Mars Global Surveyor were to start off a period of frequent missions. NASA planed on launching Mars spacecraft every two years as the planets aligned properly.

Disaster struck in 1998. Both the Mars Climate Orbiter and the Mars Polar Lander spacecraft were destroyed upon reaching Mars. The success rate increased in the coming years. Mars Odyssey , an orbiter launched in 2001, was successful. During the 2003 launch window, NASA sent the twin Mars Exploration Rovers to the red planet. The rovers, known as Opportunity and Spirit, utilized an airbag landing technique similar to that tested on the Mars Pathfinder mission. The rovers both operated for years beyond their 90 day design life. Also launched in 2003 was the European Mars Express mission. A small lander, Beagle 2, was carried to Mars on the Mars Express spacecraft. The lander failed to contact Earth and might have crashed into the surface. Mars Reconnaissance Orbiter , launched in 2005, has provided high resolution imagery of the Martian surface. The spacecraft's cameras have even captured photos of landers on the surface. The Phoenix Mars Lander , launched in 2007, landed in the polar regions.

Equipped with a robot arm, the probe was able to dig into a layer of water ice just centimeters below the surface. Landing in 2012, the large Mars Science Laboratory (MSL) rover carried a more sophisticated array of scientific instruments than recent landers. With power supplied by a radioisotope thermal generator, rather than by solar panels, MSL will be able to travel farther and faster then previous rovers. Still more missions are in the planning stages, including sophisticated rovers and sample return missions. Cronological List of Selected Mars Missions Mission Failed to enter Mars orbit. Mars 5 Entered Mars orbit, but failed after a few days Mars 6 Returned atmospheric data during descent, but did not survive landing. Mars 7 Mariner 4 Mission Mariner 3 & 4 were intended to conduct flybys of the planet Mars. Each spacecraft was launched on an Atlas-Agena D rocket (right). Mariner 3 Mariner 3 was launched on 5 November 1964. A launch shroud failed to separate and the spacecraft was not placed on the correct trajectory. Mariner 4 Mariner 4 was launched on 28 November 1964.

The spacecraft successfully flew by Mars on 14 July 1965. The mission returned the first close-up images of another planets surface. Mariner 6 & 7 Mariner 6 Mission Mariner 6 & 7 were intended to conduct flybys of the planet Mars. Each spacecraft was launched on an Atlas-Centaur rocket (right). Mariner 6 Mariner 6 (Mariner F), was launched on 24 February 1969. The spacecraft successfully flew by Mars in July 1969. The mission returned images of the Martian surface. Mariner 7 Mariner 7 (Mariner G) was launched on 27 March 1969. The spacecraft successfully flew by Mars in August 1969. The mission returned images of the Martian surface. Mariner 8 & 9 Mariner 9 Mission Mariner 8 & 9, sometimes known as "Mariner Mars 71", were intended to become the first spacecraft to enter orbit around the planet Mars. Each spacecraft was launched on an Atlas-Centaur SLV-3C rocket (right).

Mariner 8 Mariner 8 (Mariner H) was launched on 8 May 1971. A failure with the Centaur upper stage resulted in the spacecraft falling back to Earth. Mariner 9 Mariner 9 (Mariner I) was launched on 30 May 1971. The spacecraft successfully entered orbit around Mars in November 1971. The successful mission returned thousands of images of the Martian surface. Mars 2 & 3 Mars 3 Spacecraft (top) and Lander (bottom). Mission Launched in 1971, the Soviet Mars 2 and 3 missions each consisted of an orbiter and a lander component. Both missions were launched on Proton rockets from Baikonur Cosmodrome. Mars 2 Results Mars 2 was launched on 19 May 1971. The lander, released shortly before reaching Mars, malfunctioned and crashed into the surface of Mars. The Orbiter portion of the spacecraft entered orbit and returned data for several months. Mars 3 Results Mars 3 was launched on 28 May 1971.

The lander, released shortly before reaching Mars, became the first probe to successfully land on the surface of Mars. Unfortunately, communications with the lander ceased after only a few seconds. The Orbiter portion of the spacecraft entered orbit and returned data for several months. Viking Viking Orbiter & Lander Viking Mission to Mars The Viking program consisted of two spacecraft, each with an orbiter and a lander component. Each spacecraft was launched from Cape Canaveral on a Titan IIIE Centaur rocket (right). At launch, the lander was attached to the orbiter. The combined spacecraft would enter Mars orbit. Cameras on the orbiter would begin to image potential landing sites using onboard television cameras. When controllers believed a suitable landing site had been found, the lander would separate form the orbiter and begin its descent into the atmosphere. Because scientists were concerned about bacteria from Earth hitching a ride on the landers, and possibly contaminating the landing site, each lander was carefully sterilized before launch. The sterilized capsule, including heat-resistant areroshell, was encapsulated in a pressurized cocoon known as the bioshield.

The bioshield was roughly egg shaped and measured 3.7 m in diameter and was 1.9 m tall. Viking Orbiters The Viking orbiters were designed to transport the landers to Mars, to aid landing site selection and certification, to serve as a communication link with the landers, and to conduct independent investigations from Mars orbit. The orbiters were based on the successfully flown Mariner 9 spacecraft design. The core of the spacecraft was an octagon structure around 2.5 m across and 1 m tall. Four solar panels extended from the octagon. Attached to one end of the spacecraft was the encapsulated lander. Mounted to the opposite end was the main propulsion unit. The main propulsion unit included a steerable liquid fueled rocket engine fueled with monomethyl hydrazine and nitrogen tetroxide. The engine would be used for Mars orbit insertion and for major course corrections. Each orbiter had a 1.5 m steerable high-gain parabolic antenna, as well as a fixed low-gain antenna. A steerable scan platform mounted several remote sensing experiments, including a pair of television cameras, an atmospheric water detector, and a thermal mapper.

After lander deployment, the orbiters continued to observe mars from orbit, imaging the surface and conducting other experiments. (Top to bottom) Bioshield Cap, Aeroshell Cover, Viking Lander (in stowed configuaration), Aeroshell Heat Shield, Bioshield Base. Landing on Mars An aeroshell, measuring 3.5 m in diameter and coated with ablative material, protected the lander during entry into the upper Martian atmosphere. Lower in the atmosphere, a parachute measuring 16 m in diameter was deployed to further slow the descent. A radar altimeter provided altitude data during the descent. A short while later, the aeroshell was jettisoned and the landing legs deployed. Attached to the lander were three clusters of terminal descent engines. Each cluster of the hydrazine monopropellant fueled engines included 18 small nozzles. The large number of nozzles was designed to better distribute the engine exhaust, and to reduce the disturbance of soil near the landing site. As the probe neared the ground, the three terminal descent engines would fire. The engines would further slow the descent and would fire until landing.

Four smaller thrusters provided roll control during the descent Viking Mars Lander The Viking Landers The Viking landers, when fully deployed, measured around 3 m across and 2 m tall. The core of the lander was a six-sided box. The titanium and aluminum box had three 109 cm long sides, and three 56 cm sides. A landing leg was attached to each of the three short sides. Each landing leg had a circular footpad measuring 30.5 cm in diameter. Each lander was powered by a pair of radioisotope thermal generators (RTGs). Communications were made using a parabolic high-gain antenna and an omnidirectional low-gain antenna. Both antennas allowed direct communications with Earth. A UHF antenna, allowing communications with the orbiter, was also available. Two cameras and an extendable sampling arm were attached to the lander. A deployable meteorology arm mounted sensors to record temperature, wind speed, and wind direction. Sophisticated experiments on the lander included a seismometer, a gas chromatograph/mass spectrometer, an X-ray fluorescence spectrometer, and a collection of biology experiments designed to look for signs of life.

The Search for Life A biology science package included three experiments. The Gas Exchange Experiment, the Carbon Assimilation Experiment, and the Labeled Release Experiment were designed to find evidence of microscopic life in Martian soil. Each experiment was performed multiple times on different soil samples. The biology experiments gave mixed results, but provided no conclusive evidence that life existed on Mars. Viking 1 The Viking 1 spacecraft launched on 20 August 1975 and entered Mars orbit on 19 June 1976. After selecting a landing site, the lander was released on 20 July 1976. The probe successfully landed at Chryse Planitia Contact was lost with the Viking 1 lander in November of 1982. Operations with the orbiter terminated in August of 1980. Viking 2 The Viking 2 spacecraft launched on 9 September 1975 and entered Mars orbit on 7 August 1976. After selecting a landing site, the lander was released on 3 September 1976. The probe successfully landed at Utopia Planitia. The Viking 2 lander operated until 11 April 1980.

The orbiter was turned off on 25 July 1978. Viking Results Science return from the Viking probes exceeded expectations. The Viking landers returned over 4500 photos from the surface. Viking provided valuable data about weather conditions and soil composition at the landing sites. Amazingly, each of the landers continued to operate for many years. A tribute to the scientists, engineers and craftsmen who designed, constructed, tested, and operated these amazing machines. Photos of Viking Mars Lander (Test Article) Viking mars lander on display at the National Air and Space Museum. (Photos: Richard Kruse, 2008) Phobos 1 & 2 Mission Phobos 1 and 2 were a pair of Soviet interplanetary spacecraft designed to study the interplanetary environment, the planet Mars, and the surface of the Martian moon, Phobos. Near the end of their missions, each spacecraft was to deploy a pair of landers to land on Phobos. Each mission was launched on a Proton-K rocket from Baikonur Cosmodrome. Phobos 1 Phobos 1 was launched on 7 July 1988.

Communication with the spacecraft failed in September 1988 before reaching Mars. Phobos 2 Phobos 2 was launched on 12 July 1988. The spacecraft successfully entered orbit around Mars in January 1989. Unfortunately, contact was lost in March 1989, before the Phobos landers were released. Mars Observer Mars Observer was launched on 25 September 1992, from Cape Canaveral, on a Titan III rocket (right). Contact with the probe was lost in August 1993. The loss occurred several days before the Mars orbit insertion burn. Investigators believe a fuel line may have ruptured during fuel tank pressurization. No further contact was made with the spacecraft. Mars Global Surveyor Mars Global Surveyor Mission Mars Global Surveyor was launched on 7 November 1996 on a Delta II 7925 rocket . The spacecraft arrived at Mars in September 1997. The successful mission continued to operate until communication was lost in November 2006.

Mars Global Surveyor Scientific Instruments Mars Orbiter Camera (MOC) - Acquired narrow-angle and wide-angle images of weather patterns and surface features. Mars Orbiter Laser Altimeter (MOLA) - Gathered data used to create accurate topographical maps of the surface. Thermal Emission Spectrometer (TES) - Mapped the mineralogical composition of the planets surface. MAGNETOMETER - Gathered data on regional variations in the Martian magnetic field. Gravity Field Experiment - Scientists used signals from the spacecraft as it disappeared and reappeared from behind the planet to study the Martian atmosphere. Mars Relay System - Allows the orbiter to relay data between landers on the surface and controllers back on Earth. Mars Pathfinder (Discovery 1) Mars Pathfinder lander and Sojourner rover. The Mission The Pathfinder mission was designed to demonstrate a less expensive method for landing spacecraft on Mars. The mission also deployed a small rover to investigate the nearby surface. The mission was launched on 4 December 1996 from Cape Canaveral Air Station in Florida. The launch vehicle was a Delta-II rocket (right). Landing on Mars Mars Pathfinder cruise stage, heatshield and backshell.

Pathfinder successfully landed on Mars on 4 July 1997. Unlike Viking, Pathfinder did not enter Mars orbit before starting its descent. Instead, the spacecraft entered directly into the atmosphere. A heat shield protected the spacecraft during the early stages of entry. As the velocity slowed, a parachute was deployed. As the velocity slowed more, the heat shield was dropped. Then the lander was suspended from the backshell on a tether. As the spacecraft neared the ground, a number of large airbags inflated, completely covering the folded, four-sided lander. Thrusters fired to cancel out much of the remaining vertical velocity and the tether was cut. The lander dropped the remaining few meters to the Martian surface. The bags protected the spacecraft when it made contact with the rocky ground. After bouncing and eventually coming to rest, the bags deflated and were retracted. By deploying three large petals, the spacecraft opened up and exposed the camera mast, weather station, high-gain antenna, solar panels, and rover. Sojourner Rover The Rover The six-wheeled rover, named Sojourner, was equipped with cameras and an Alpha-Proton-X-ray Spectrometer (APXS).

The APXS instrument was used to determine the chemical composition of rocks and soil. The rover was solar powered. Results The last transmission from the lander occurred on 27 September 1997. The probe had functioned for much longer than required by the mission objectives. The experience gained operating the rover, as well as the successful use of the airbag landing system, proved critical to the later success of the larger and more capable Mars Exploration Rover missions launched in 2003. Mars Pathfinder Model These photographs were taken at the Udvar Hazy Center. (Photos: Richard Kruse, 2009) Mars 96 The Russian Mars 96 mission failed due to a booster failure in 1996. In addition to an orbiter, the Mars-96 mission was to deploy a pair of surface landers. These photographs are of a surface lander engineering model on display at the Udvar Hazy Center. (Photos: Richard Kruse, 2009) Nozomi (Planet-B) Nozomi (Planet-B) Mission A Japanese Mars orbiter launched on 3 July 1998 on an M-5 rocket from Uchinoura Space Center, Japan.

The original plan was to enter Mars orbit in October 1999. Unfortunately, a problem with the fuel system left the spacecraft unable to reach its planned rendezvous. Mission planners developed a new trajectory that would reach Mars in December 2003, four years later then originally planned. More problems arose and the spacecraft did not enter Mars orbit. Mars Climate Orbiter (MCO) Mars Climate Orbiter Mission Mars Climate Orbiter was designed to study aspects of the Martian atmosphere. The mission was launched on a Delta II 7425 rocket on 11 December 1998 from Cape Canaveral. The spacecraft reached Mars in September 1999, but failed to enter orbit as planned. No further contact was made with the spacecraft. Investigators believe a navigation error resulted in the probe impacting the planets atmosphere and breaking up. Mars Climate Orbiter Science Instruments Mars Color Imager (MARCI) - An assembly of two cameras, wide angle and medium angle, to image the Martian atmosphere and surface. Pressure Modulator Infrared Radiometer (PMIRR) - Designed to analyze the vertical structure of the Martian atmosphere.

Mars Polar Lander (MPL) Mars Polar Lander Mission Mars Polar Lander was designed to study surface conditions in the southern polar regions of Mars. The lander was equipped with a robotic arm to gather samples for analysis. The mission was launched on a Delta II 7425 rocket on 3 January 1999 from Cape Canaveral. The spacecraft entered the Martian atmosphere on 3 December 1999. No contact was made with the lander during descent or after the scheduled landing. The spacecraft is believed to have crashed into the surface. Mars Polar Lander Science Instruments Mars Volatiles and Climate Surveyor (MVACS) - A package of equipment that included a stereo imager, a robotic arm, a weather station, and a gas analyzer. Mars Descent Imager (MARDI) - Designed to take surface images during the landers descent. Light Detection and Ranging (LIDAR) - Designed to study particles in the Martian atmosphere. Deep Space 2 Microprobes A pair of small probes, designed to penetrate the surface and analyze subsurface conditions, were transported to Mars attached to the Mars Polar Lander spacecraft. The probes were known as Deep Space 2.

No contact was made with either microprobe at Mars and are believed to have been destroyed. Mars Odyssey Mars Odyssey Mission The American Mars Odyssey orbiter was launched on 7 April 2001 on a Delta II 7925 from Cape Canaveral. The goal of the mission was to study the mineralogical composition of the planets surface and to investigate the radiation environment near the planet. The spacecraft arrived at Mars in October 2001 and continued to operate after successfully completing its primary mission in 2004. Mars Odyssey Science Payload Mars Odyssey carried three scientific instruments. Mars Radiation Environment Experiment (MARIE) Measures the radiation environment near Mars. Thermal Emission Imaging System (THEMIS) Measures the mineralogical composition of the surface. Gamma-Ray Spectrometer (GRS) Gathers information about the elemental composition of the surface. The instrument can also measure the amount of hydrogen near the planets surface. Mars Express Mars Express Mission The European Mars Express mission was launched on 2 June 2003. Liftoff took place from Baikonur Cosmodrome on a Soyuz-Fregat rocket. The spacecraft entered Mars orbit in December 2003.

On 19 December 2003, Mars Express released the Beagle 2 lander. No contact was made with the lander after the scheduled landing. The Mars Express spacecraft continues to study Mars using a variety of instruments. Mars Express Scientific Instruments High Resolution Stereo Camera (HRSC) - Will image the entire planet with a resolution around 10 meters. Some areas will be imaged at 2 meter resolution Visible and Infrared Mineralogical Mapping Spectrometer (OMEGA) - Maps the mineral composition of the planets surface. Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) - Gathers data on the subsurface structure of the planet. Mars Radio Science Experiment (MaRS) - Uses radio waves to gather information about the Martian ionosphere, atmosphere, surface, and interior. Spectroscopic Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) - Gathers data on the composition of the Martian atmosphere. Planetary Fourier Spectrometer (PFS) - Gathers data on the composition of the Martian atmosphere. Analyzer of Space Plasmas and Energetic Atoms (ASPERA) - Gathers data on the composition of the Martian atmosphere.

Beagle 2 Mars Lander Mission Launched with the Mars Express orbiter in 2003, Beagle 2 was designed to land on Mars. It's mission was to search for signs of present or past life on the surface. Unfortunately, no confirmation of landing was received. All attempts to contact the Lander failed. Beagle 2 Model Photographs are of a model at the London Science Museum. (Photos: Richard and Sharron Kruse, 2009) Mars Exploration Rovers (MER) MER Spacecraft and Rover Mission The United States launched a pair of Mars Exploration Rovers in 2003. The spacecraft used the airbag landing technique first used on the Mars Pathfinder mission. A major goal of the mission was to search for evidence of past water activity. Each rover landed successfully and operated for far longer then their design life of 90 days. Spirit (MER-A) Spirit was launched on a Delta II 7925 rocket on 10 June 2003 from Cape Canaveral. Spirit landed on 4 January 2004 at Gusev Crater.

The rover operated until 2010, far exceeding its design live of 90 days. Opportunity (MER-B) Opportunity was launched on a Delta II 7925H rocket on 7 July 2003 from Cape Canaveral. The later launch of Opportunity required a more powerful rocket then Spirit needed. Opportunity landed on 25 January 2004 at Meridiani Planum . The mission has proved highly successful and the rover continues to operate. Mars Exploration Rovers Scientific Instruments Panoramic Camera (Pancam) - A pair of high-resolution cameras mounted on a mast. The cameras can pan and tilt to image the surrounding surface and sky. The cameras are fitted with filter wheels and can capture multispectral and color images. Microscopic Imager (MI) - Located on the robotic arm, this device can take microscopic images of rock and soil samples. Miniature Thermal Emission Spectrometer (Mini-TES) - An infrared spectrometer that determines the composition of rocks and soils by analyzing their thermal radiation patterns. Mössbauer Spectrometer (MB) - A spectrometer designed to analyze iron-bearing minerals.

Alpha Particle X-Ray Spectrometer (APXS) - A spectrometer used to analyze the composition of rock and soil samples. Rock Abrasion Tool (RAT) - A small grinder, located on the robotic arm, that can grind away the weathered outer layers of rocks, exposing a cleaner surface for further investigation using the rovers other instruments. Mars Reconnaissance Orbiter (MRO) Mars Reconnaissance Orbiter Mission The Mars Reconnaissance Orbiter is equipped with an array of scientific instruments to gather information about the history of water on Mars. The spacecraft can also serve as a communication relay to and from landers and rovers. The Mars Reconnaissance Orbiter was launched on an Atlas V-401 rocket from Cape Canaveral Air Force Station, Florida. Liftoff occurred on 12 August 2005. The spacecraft measures around 13.6 meters from one solar panel tip to the other. A 3 meter high-gain antenna allows high volumes of data to be transmitted to Earth. MRO entered Martian orbit on 10 March 2006. The spacecraft continues to operate. Mars Reconnaissance Orbiter Science Instruments MRO carries six scientific instruments.

Three cameras, an atmospheric sounder, a subsurface sounding radar, and an imaging spectrometer. High Resolution Imaging Science Experiment (HiRISE) The largest telescopic camera sent to another planet, HiRISE is capable of resolving surface details smaller then a meter in size. Context Camera (CTX) - Captures wide-area images to provide context for the high resolution images. Mars Color Imager (MARCI) - Used to image weather features such as clouds and dust storms. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) - A spectrometer used to identify minerals on the surface. Mars Climate Sounder (MCS) - Observes characteristics of the Martian atmosphere. Shallow Subsurface Sounding Radar (SHARAD) - Looks for signs of water ice below the Martian surface. Phoenix Mars Lander Phoenix Mars Lander Mission Phoenix was launched on 4 August 2007 on a Delta II 7925 rocket from Cape Canaveral Air Force Station, Florida. Phoenix successfully landed in the northern polar region of Mars on 25 May 2008. The spacecraft conducted analysis of soil and ice samples collected with a robotic arm.

Phoenix Mars Lander Science Instruments In addition to a robotic arm, the lander included the following experiments. Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) - Measures the properties of soil samples. Robotic Arm Camera (RAC) - Mounted near the scoop at the end of the Robotic Arm, the RAC acquires close-up images of the Martian surface. Surface Stereo Imager (SSI) - Acquires high-resolution, stereo, panoramic images of the surrounding area. Thermal and Evolved Gas Analyzer (TEGA) - Analyzes the composition of up to eight soil and ice samples. Meteorological Station (MET) - Collects weather data near the lander. Mars Science Laboratory Mars Science Laboratory The Mission Mars Science Laboratory (MSL), also known as Curiosity, successfully landed on Mars on 8 August 2012. The rover carries a sophisticated suite of instruments designed to look for evidence of conditions capable of supporting microbial life, now or in the past, on the planet Mars. MSL is the largest and most capable rover to explore the red planet. The Spacecraft The six wheel drive rover was designed to operate for at least one Martian year (687 Earth days).

Power is provided by a Radioisotope Thermoelectric Generator, or RTG. The RTG generates both electricity and heat from the radioactive decay of plutonium-238. A 5 degree-of-freedom robotic arm is mounted on the front of the rover. A turret, on the end of the arm, includes several instruments for analyzing and collecting samples. In addition to a spectrometer and an imaging instrument, the turret includes a brush, drill, scoop and sieves. A mast, extending approximately two meters above the planets surface, supports several cameras and experiments. Cameras and Instruments Mast Camera (Mastcam) - A pair of cameras mounted on the mast, approximately two meters above the planets surface. Each camera has a different fixed focal length. The cameras are equipped with a variety of filters and are capable of taking color images. Chemistry & Camera (ChemCam) - The ChemCam consists of two components. The Induced Breakdown Spectrometer (LIBS) uses laser pulses and a spectrometer to remotely gather elemental composition data on rock and soil samples within several meters of the rover. The Remote Micro-Imager (RMI) serves as a context imager for the LIBS instrument. The ChemCam is mounted on the mast.

Alpha Particle X-ray Spectrometer (APXS) - Mounted on the robotic arm turret, the APXS is a spectrometer capable of determining elemental chemistry of rock and soil samples. Less capable versions of this experiment equipped the earlier Sojourner and Mars Exploration Rovers. Mars Hand Lens Imager (MAHLI) - A camera imager capable of close-up, high resolution, color images of rock and soil samples. The imager is mounted on the robotic arm turret. Mars Descent Imager (MARDI) - A downward pointing color video camera that will image the area around the landing site as the rover descends to the surface. The data gathered will be used to identify local terrain features and to help plan an exploration strategy. Radiation Assessment Detector (RAD) - An instrument to detect various forms of high-energy radiation near the Martian surface. Information gathered will be used to better understand the radiation levels that future human Mars missions will encounter. Dynamic Albedo of Neutrons (DAN) - Funded by Russia, the DAN experiment will measure hydrogen concentrations beneath the surface. Detected hydrogen might indicate the presence of water.

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin) - Will be used to identify and measure concentrations of minerals in Martian rock samples. Sample Analysis at Mars (SAM) - The SAM is a suite of sophisticated instruments designed to analyze soil and rock samples collected from the surface and delivered to the instruments. Included within the SAM is a mass spectrometer, a tunable laser spectrometer and a gas chromatograph. Launch Vehicle MSL launched on an Atlas V 541 launch vehicle (right). The rocket lifted off from launch complex 41 at Cape Canaveral Air Force Station in Florida on 26 November 2011. The Atlas V 541 includes an Atlas V core, four solid rocket motors, and a Centaur upper stage. Entry, Descent, and Landing MSL began it's descent into the Martian atmosphere encapsulated in an aeroshell and heat-shield. As the spacecraft entered thicker atmosphere, a parachute deployed to slow the descent rate. Near the surface, the parachute and aeroshell separated from the spacecraft. A structure, mounted above the rover, fired several rockets that further slowed the descent rate.

As the surface neared, the rover descended on a tether and was gently lowered to the ground as the rocket propelled "sky crane" hovered above. Once on the surface, the tether was cut and the hovering structure flew away and impacted the surface a safe distance from the rover. The rover, safely on the surface, began testing systems and deploying instruments. Previous Mars Rovers The United States had previously operated three rovers on Mars. The first rover, known as Sojourner, was part of the highly successful Mars Pathfinder mission launched in 1996. The solar powered rover spent several months exploring near the Pathfinder lander. The twin Mars Exploration Rovers , known as Spirit (MER-A), and Opportunity (MER-B), were launched on separate Delta II rockets in 2003. Each rover successfully landed on the red planet in January of the following year. The rovers, designed to operate for three months on Mars, far exceeded their design life. Spirit operated for around six years. Opportunity continues to operate, nearly eight years after landing. Moon Rovers Five rovers have operated on the lunar surface.

Two unmanned rovers, known as Lunokhod 1 and 2, were operated by the Soviet Union during the early 1970's. The Lunokhod rovers were remotely controlled by engineers on Earth. The last three Apollo lunar missions each included a Lunar Roving Vehicle , or LRV. The battery powered LRV was designed to transport two astronauts on traverses of up to several kilometers from the lunar module . More Information About Mars Science Laboratory Mars Science Laboratory Fact Sheet (PDF) , JPL 400-1416, 2011. Mars Orbiter Mission The Mars Orbiter Mission (MOM) represents India's first mission to another planet. The spacecraft was developed by the Indian Space Research Organization (ISRO). The mission was launched in November 2013 on a PSLV-XL rocket . More Information About the Mars Orbiter Mission Mars Mystery Deepens: Curiosity Rover Finds No Sign of Methane Mars Mystery Deepens: Curiosity Rover Finds No Sign of Methane By Charles Q.

Choi , SPACE.com Contributor | September 19, 2013 02:01pm ET MORE NASA's Mars rover Curiosity took this self-portrait, composed of more than 50 images using its robotic arm-mounted MAHLI camera, on Feb. 3, 2013. The image shows Curiosity at the John Klein drill site. A drill hole is visible at bottom left. Credit: NASA/JPL/MSSS/Marco Di Lorenzo/Ken Kremer NASA's Mars rover Curiosity has revealed no trace of methane, a potential sign of primitive life, on the Martian surface, contradicting past evidence of the gas spotted by spacecraft orbiting the Red Planet, researchers say. The Mars methane discovery, or rather the lack thereof, adds new fuel to the debate over whether the gas is truly present on Mars. And not all scientists are convinced that methane is missing on Mars . The first and only attempts to search for life on Mars were the Viking missions, launched in 1975. Those probes failed to find organic compounds in Martian soils, apparently ruling out the possibility of extant life on the Red Planet.

[ 7 Biggest Mars Mysteries of All Time ] But in the past decade, probes orbiting Mars and telescopes on Earth have detected what appeared to be plumes of methane gas from the Red Planet. The presence of colorless, odorless, flammable methane on Mars , the simplest organic molecule, helped revive the possibility of life once existing, or even currently living, just below the planet's surface. On Earth, much of the methane in the atmosphere is released by life-forms, such as cattle. Scientists have suspected that methane stays stable in the Martian atmosphere for only about 300 years, so whatever is generating this gas did so recently. Now, the new findings from NASA's Curiosity rover unveiled online today (Sept. 19) in the journal Science suggest that, at most, only trace amounts of methane exist on Mars. "Because methane production is a possible signature of biological activity, our result is disappointing for many," said study lead author Christopher Webster, an Earth and planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. But the findings still puzzle scientists.

"It's a mystery surrounded by an enigma here," said imaging physicist Jan-Peter Muller of University College London, who is a Curiosity rover science team member but is not one of the authors of this latest Mars methane study. "This clearly contradicts what has been measured from space and from Earth." Methane mystery on Mars The Curiosity rover has analyzed the surface and atmosphere of Mars with an arsenal of advanced scientific instruments ever since its spectacular landing on Mars in August 2012. Measurements from the rover's Tunable Laser Spectrometer, a device specially designed for measuring the gas on Mars, say the most methane that could currently exist in the Martian atmosphere is 1.3 parts per billion by volume. [ Latest Mars Photos by the Curiosity Rover ] "Based on earlier observations, we were expecting to land on Mars and measure background levels of methane of at least several parts per billion, but saw nothing," Webster told SPACE.com. When the researchers first looked for methane using Curiosity, they found strong signals that they quickly realized were coming from the little methane that they had taken with them, Webster said — that is, "'Florida air' that had leaked into one chamber during the long prelaunch activities.

This contamination has been removed in stages, but each attempt to look for methane from the Mars atmosphere has resulted in a non-detection." The original plan of the researchers was to analyze the carbon isotope ratios of methane on Mars to get insight on whether that gas could be biologically produced. "However, the lack of significant methane has denied that latter experiment," Webster said. This new measurement is about six times lower than previous estimates of methane levels on Mars. Webster and his colleagues suggest this severely limits the odds of methane production by microbes below the surface of Mars or from rock chemistry. "It's an excellent piece of science," Muller told SPACE.com. "However, it's not to say that what is measured 1 meter (3 feet) above the ground is representative of the atmosphere in total — that's a matter of interpretation, not necessarily a matter of fact." Is the methane hiding? For instance, past measurements of methane in the atmosphere of Mars analyzed a region much higher above the surface, "so these might be very different measurements," Muller said.

"It does leave a little wiggle room in terms of interpretation." Moreover, when it comes to places on Earth where methane leaks out, scientists can detect large volumes of methane right at the plumes but practically none away from them, Muller said. "It's difficult to know whether the null measurement from Curiosity has to do with being in the wrong place at the wrong time, or whether it is representative of Mars," Muller said. "We are often asked if our measurements at Gale Crater represent the planet as a whole," Webster noted. "We remind others that the lifetime of methane on Mars is very long, about 300 years, compared to the short mixing time — months — for the whole atmosphere, so we feel our measurement does represent the global background value." Curiosity experiment may hold the key The Sample Analysis at Mars suite of instruments on Curiosity has yet to conduct a "methane enrichment" experiment that will increase the sensitivity of the rover's Tunable Laser Spectrometer even further — by a factor of at least 10, Webster said. "It's possible that we may then see methane at extremely low levels — or, alternatively, we will not, and our upper limit will go down much further," he added.

The ExoMars spacecraft, planned for launch in 2016, will study the chemical composition of Mars' atmosphere to learn more about any methane there. "It can look at the vertical distribution of methane on Mars, see if it's lofted some way high up in the atmosphere or if it's near the ground," Muller said. "If it's near the ground, that's likely reflective of it seeping out of the ground; if it's high in the atmosphere, some exotic photochemical process may be responsible." Webster stressed that Curiosity will continue its mission to assess the habitability of Mars . "The Curiosity rover will continue to make its measurements of both atmosphere and rock samples to discover if organics other than methane exist on Mars," Webster said. "To that end, the jury is still out, as these important measurements are being made in a series of studies that will extend many months into the future. Stay tuned!" Life on Mars Found by NASA's Viking Mission? Life on Mars Found by NASA's Viking Mission? New analysis suggests robots discovered microbes in 1976. View Images A picture of the Martian surface, as seen by NASA's Viking 2 lander in 1976.

Image courtesy NASA A fresh look at NASA data suggests that a robotic mission uncovered microbial life on Mars —more than 30 years ago. Related Content Nice Shot! A Martian Selfie In 1976 NASA sent two space probes, Vikings 1 and 2 , to Mars to determine whether life exists on the red planet. The probes carried three experiments specially designed for the task, one of which was called the Labeled Release (LR) apparatus. The LR experiment worked by scooping up a bit of Martian soil and mixing it with a drop of water that contained nutrients and radioactive carbon atoms. (Related: "Mars Soil Resembles Veggie-Garden Dirt, Lander Finds." ) The idea was that if the soil contained microbes, the life-forms would metabolize the nutrients and release either radioactive carbon dioxide or methane gas, which could be measured by a radiation detector on the probe. A number of control experiments were also performed, including heating some Mars soil samples to different temperatures and isolating other samples in the dark for months—conditions that would kill microbes that are photosynthetic or that rely on photosynthetic organisms for survival. These control samples were also mixed with the nutrient solution.

To the delight of many biologists at the time, the LR experiment came out positive for life, and the control experiments came out negative. "The minute the nutrients were mixed with the soil sample, you got something like 10,000 counts" of radioactive molecules—a huge spike from the 50 or 60 counts that constituted the natural background radiation on Mars, said study team member Joseph Miller , a neurobiologist at the University of Southern California and a former NASA space shuttle project director. Unfortunately, the LR experiment results were not backed up by the probes' other two experiments, both of which came out negative for life, so the space agency dismissed the possibility. (Related: "Viking Mission May Have Missed Mars Life, Study Finds." ) Now, after running Viking's LR data through a mathematical test designed to separate biological signals from nonbiological signals, Miller's team believes that the LR experiments did indeed find signs of microbial life in Martian soil. "It's very possible that if you have microbes, they're living a couple of inches beneath the soil, close to water ice," he said.

Clustering Viking's Mars Data For the study, Miller and mathematician Giorgio Bianciardi, of Italy's University of Siena , used a technique called cluster analysis, which groups together similar-looking data sets. "We just plugged all the [Viking experimental and control] data in and said, Let the cluster analysis sort it," Miller said. "What happened was, we found two clusters: One cluster constituted the two active experiments on Viking and the other cluster was the five control experiments." To bolster their case, the team also compared the Viking data to measurements collected from confirmed biological sources on Earth—for example, temperature readings from a rat—and from purely physical, nonbiological sources. "It turned out that all the biological experiments from Earth sorted with the active experiments from Viking, and all the nonbiological data series sorted with the control experiments," Miller said. "It was an extremely clear-cut phenomenon." (Related: "Life on Mars? 'Missing Mineral' Find Boosts Chances." ) The team concedes, however, that this finding by itself isn't enough to prove that there's life on Mars.

"It just says there's a big difference between the active experiments and the controls, and that Viking's active experiments sorted with terrestrial biology and the controls sorted with nonbiological phenomena," Miller said. Evidence for Martian Rhythm Still, the new findings are consistent with a previous study published by Miller, in which his team found signs of a Martian circadian rhythm in the Viking LR experiment results. Circadian rhythms are internal clocks found in every known life-form—including microbes—that help control biological processes, such as waking, sleeping, and temperature regulation. (See "Sleep Preferences Predict Baseball Success, Study Says." ) On Earth this clock is set to a 24-hour cycle, but on Mars it would be about 24.7 hours—the length of a Martian day. In his previous work, Miller noticed that the LR experiment's radiation measurements varied with the time of day on Mars. "If you look closely, you could see that the [radioactive-gas measurement] was going up during the day and coming down at night. ... The oscillations had a period of 24.66 hours just about on the nose," Miller said.

"That is basically a circadian rhythm, and we think circadian rhythms are a good signal for life." Waiting for the Video Despite his own conviction that the Viking mission detected life on Mars, Miller said he doesn't expect most people will be convinced until they can look at a video of Martian bacteria sitting in a petri dish. "But for some reason, NASA has never flown a microscope that would let you do something like that," he said. "If they can fly a microscope for the geologists, they should be able to fly one for the biologists." NASA's next Martian mission—the Mars Science Laboratory , aka Curiosity—will arrive on the red planet later this year. Although it's not carrying such a microscope, Miller thinks the lander could find supporting evidence for his team's theory. (Related: "Next Mars Rover Landing Site Named: Gale Crater." ) "It won't test the hypothesis [for life on Mars] directly, but I think they'll be able to detect methane," Miller said.

"And if they see a circadian rhythm in the methane release into the atmosphere, it would be very consistent with what we saw." StarChild: Probes to Mars Probes to Mars Vikings 1 and 2 became the first space probes to successfully land on the surface of Mars. Viking Lander 1 was the first U.S. spacecraft to successfully touch down on any planet other than Earth. Both spacecraft were launched in 1976, the year in which the United States celebrated its bicentennial. The Viking probes analyzed gases in the Martian atmosphere and chemicals in the soil for evidence of the existence of simple life. The probes also measured wind speed, wind direction, atmospheric temperature, and atmospheric pressure. The Viking orbiters mapped the Martian surface. A Viking Lander In November of 1996, Mars Global Surveyor began a 10 month mission to the Red Planet. With the start of its journey, Surveyor became the sixteenth space probe to fly-by, orbit , or land on Mars. The space probe will be caught by Mars' gravitational pull and will swing into an elliptical orbit around the planet. Onboard detectors will measure radiation to determine the minerals that make up Mars.

The detectors will also measure the composition, pressure, water content, dust content, and changes in the Martian atmosphere. This study of Mars will continue for two years. At its completion, the Surveyor mission will have compiled an extensive record of the planet. This information will help in the planning of future missions which may include human landings. On July 4, 1997, after a 7 month journey, Pathfinder entered the Martian atmosphere. Minutes later, its airbag-cocooned lander bounced to a stop on the Martian surface. The Pathfinder Lander, now known as the Sagan Memorial Station, carried onboard a robotic rover named Sojourner. The 10 kilogram solar-powered rover was equipped with a spectrometer used to analyze the chemical composition of Martian rock and a camera which relayed images of the landscape back to Earth. The Pathfinder lander and the Sojourner rover sent thousands of images, more than 15 analyses of Martian rocks and data on weather condition to scientists on Earth. The low-cost mission has been said to set the standard for 21st century space exploration.

The Latest From Mars As part of their mission to explore Mars, NASA launched twin robotic rovers on June 10 and July 7, 2003. For landing, each rover was encased in a beach ball - like apparatus with a parachute attached. After impact, the lander bounced along the Martian surface, eventually rolling to a stop. The airbag then deflated and retracted, exposing the rovers. Both rovers landed during the Martian afternoon while Earth was still in view. This allowed the rovers to communicate with Earth via the Deep Space Network, letting scientists know they had landed safely. The Network is a series of antennae located in California, Spain, and Australia; it allows the rovers to send scientific data to Earth and allows scientists on Earth to send commands to the rovers on Mars. The rovers, named Spirit and Opportunity, landed on the Martian surface approximately three weeks apart in January, 2004. The rovers were sent with the specific goals of locating and examining soils and rocks that might hold clues to past water activity on Mars. The rovers landed in different regions of the planet. The landing sites were chosen because previous observations had suggested water activity in the areas.

The rovers carry various scientific instruments that aid the scientists in their long distance exploration. The panoramic camera helps determine the texture and structure of the terrain. Spectrometers are used for analysis of soil, rock, and atmospheric samples. A microscopic imager is used to collect high resolution images of soil and rock particles. There is also a rock abrasion tool that removes weathered surfaces from rocks, exposing fresh materials for examination by the imager and spectrometers. The scientists move the rovers approximately 40 meters per day, examining the terrain as progress is made. The rovers were designed to last a minimum of 90 days on the Martian surface. Spirit and Opportunity are solar powered. The longer they are on the surface, the thicker the layer of dust that collects on the solar panels, blocking out their power source. Also, as Mars continues on in its orbit, it temporarily moves farther away from the Sun, further decreasing the sunlight reaching the solar cells. Eventually the batteries will lose their ability to power the rover activities and telecommunications will be lost. As of January 1, 2009 the rovers are still in service. So what have the two rovers found?

Lots and lots of evidence that liquid water was once plentiful on the surface of Mars! Among this evidence, they have found crystals that only grow in the presence of water, and rock formations which could only have been carved by flowing liquid water.

Question: Which space probes failed to find life on Mars?
Answer: Viking probes