This is a story about the conquest of Mars — by robots.
The First Landers and Biology Assessments
The first machines from Earth to reach the Martian surface were made by the Soviet Union. The Mars 2 lander crashed there on 27 November 1971 and Mars 3 successfully made a soft landing on December 2, 1971.
Unfortunately contact was lost with Mars 3 only 14.5 seconds after landing in a dust storm. Further Soviet attempts in 1973 crashed or failed to enter the atmosphere.
The US Viking 1 lander was the first to return clear pictures from the Martian surface, arriving on July 20, 1976, joined on September 3 by Viking 2.
The Viking probes included the first attempts to assess Mars for bacterial biosignatures. Soil samples were heated and the effluent examined for organic compounds by a gas chromatograph-mass spectrometer. No organics were detected.
The biology experiment mixed soil samples with radioactively labeled nutrients in water and the gases produced were tested for radioactivity. The soil did instantly produce radioactive gases when this was done, but the absence of organic compounds, and the lack of any time delay for bacterial growth to occur before the radioactive gases were seen, lead most researchers to conclude that the effects were caused by some unknown chemical soil constituent rather than by bacterial metabolism.
The detection of significant amounts of perchlorates (ClO4−) in Martian soil by the Phoenix Mars lander in 2008 supplied the missing piece of chemistry for the Viking biology experiments. When mixed with water, perchlorates react with organic carbon to produce carbon dioxide. The labeled organic carbon in the Viking nutrient solution had likely reacted with the perchlorate in Martian soil and generated radioactive carbon dioxide. That explains the lack of any time delay for labeled gas to be detected. It was, indeed, chemistry, not biology. The apparent complete absence of native organics (carbon-hydrogen compounds) in Martian soil also could be a result of perchlorate reacting with them when heated for the gas chromatograph, again converting any organic carbon present into carbon dioxide.
Rovers
Although some of the Soviet attempts had included rovers, the first rover to operate successfully on Mars was Sojourner, the rover for the Mars Pathfinder mission, which landed on July 4, 1997.
Intended to operate for 7 sols (Martian days), Sojourner operated for 83 sols.
In 2004, NASA’s Mars Exploration Rover Mission landed two more rovers on Mars: Spirit and Opportunity. Spirit became stuck in soft soil in 2009 and was repurposed as a stationary observation platform. Contact was lost with Spirit in 2010.
Opportunity is still operating as a rover today, in 2016.
Opportunity has returned a treasure trove of information about how Mars has evolved as a planet. It investigated hematite-rich Martian nodules — aka “blueberries” — generally considered to be water-formed concretions made during a period some 3+ billion years ago when the water table rose and then fell at the landing site in Meridiani Planum.
In fact, Opportunity’s landing site was chosen because spectral data from orbit, obtained by Mars Global Surveyor, showed hematite at that location.
Hematite concretions on Earth are associated with water -- and with biomineralization by bacteria. Of course we don’t know yet whether Martian blueberries were made with the help of bacteria.
Our current flagship rover on Mars is of course, Mars Science Laboratory, better known as Curiosity, which landed in Gale Crater 10:32 p.m. Aug 5 2012 (PDT, which is JPL time!)
Curiosity was designed to determine whether Mars was ever habitable (by bacteria) — and the answer is: yes it was. Chemicals that could support extremophile bacterial metabolisms are there. Water was once abundant in Gale Crater. This determination does not mean that Mars is known to have once had bacteria, only that it could have had them. Curiosity was never designed to perform a definitive detection of life on present-day Mars, but it has seen a couple of intriguing methane spikes.
Curiosity also carries an organic chemistry lab called Sample Analysis at Mars (SAM). SAM unfortunately has not been an unqualified success; it became contaminated with N-Methyl-N-tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA) at some point before or during arrival on Mars, which has confounded the ambitious organic chemistry plans. MTBSTFA is used in SAM’s wet-chemistry cells to stabilize organic compounds before heating for the gas chromatograph. It seems to have leaked. This makes it impossible to distinguish native Martian organics from the MTBSTFA contamination.
In fact, NASA has not included a SAM follow-on in the experiments selected for its next Mars rover, Mars 2020, instead opting to begin working toward sample returns. However, the European Space Administration has chosen to pursue sample analysis for exobiology on the Martian surface.
Coming Attractions
The next NASA lander planned for Mars, Mars InSight, is a stationary lander to study the Martian interior and the thermal history of the planet. Originally scheduled to launch in March of 2016, it is on hold because of problems with the seismometer. The next launch window will be in two years.
Two European Space Administration missions focusing on exobiology — ExoMars 2016 and ExoMars 2018 — are next in line for Mars. ExoMars Trace Gas Orbiter and Schiaparelli Mission (2016), scheduled for launch in March 2016, is an orbiter to look for possible biosignature gases (methane and other trace gases that might indicate the presence of life) to help choose an optimal landing site for ExoMars 2018. ExoMars 2016 also has a test lander, Schiaparelli, which will permit a live test of ESA’s landing system.
ExoMars 2018 will have a surface science platform and a rover to collect samples for analysis by a mass spectrometer (MOMA) provided by NASA. It will be able to drill to a depth of 2m to look for evidence of subsurface life. The final landing site will be chosen once ExoMars 2016 data are available, but there has been interest in picking a site with access to Martian brine.
The next NASA Mars rover will be Mars 2020, similar to Curiosity but with better geology instruments. Mars 2020 will also have manipulators and a drill for sample collection. The current plan is to cache samples chosen from various sites it visits for a series of future missions (still in concept phase) to collect and return to Earth.
The selected Mars 2020 payload proposals are:
- Mastcam-Z, an advanced camera system with panoramic and stereoscopic imaging capability with the ability to zoom. The instrument also will determine mineralogy of the Martian surface and assist with rover operations. The principal investigator is James Bell, Arizona State University in Tempe.
- SuperCam, an instrument that can provide imaging, chemical composition analysis, and mineralogy. The instrument will also be able to detect the presence of organic compounds in rocks and regolith from a distance. The principal investigator is Roger Wiens, Los Alamos National Laboratory, Los Alamos, New Mexico. This instrument also has a significant contribution from the Centre National d'Etudes Spatiales,Institut de Recherche en Astrophysique et Plane'tologie (CNES/IRAP) France.
- Planetary Instrument for X-ray Lithochemistry (PIXL), an X-ray fluorescence spectrometer that will also contain an imager with high resolution to determine the fine scale elemental composition of Martian surface materials. PIXL will provide capabilities that permit more detailed detection and analysis of chemical elements than ever before. The principal investigator is Abigail Allwood, NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
- Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC), a spectrometer that will provide fine-scale imaging and uses an ultraviolet (UV) laser to determine fine-scale mineralogy and detect organic compounds. SHERLOC will be the first UV Raman spectrometer to fly to the surface of Mars and will provide complementary measurements with other instruments in the payload. The principal investigator is Luther Beegle, JPL.
- The Mars Oxygen ISRU Experiment (MOXIE), an exploration technology investigation that will produce oxygen from Martian atmospheric carbon dioxide. The principal investigator is Michael Hecht, Massachusetts Institute of Technology, Cambridge, Massachusetts.
- Mars Environmental Dynamics Analyzer (MEDA), a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity and dust size and shape. The principal investigator is Jose Rodriguez-Manfredi, Centro de Astrobiologia, Instituto Nacional de Tecnica Aeroespacial, Spain.
- The Radar Imager for Mars' Subsurface Exploration (RIMFAX), a ground-penetrating radar that will provide centimeter-scale resolution of the geologic structure of the subsurface. The principal investigator is Svein-Erik Hamran, the Norwegian Defense Research Establishment, Norway.