The story of how technology has changed how we see Mars.
By: Nicole Willett
The ability to see is one of the most important aspects in astronomical discovery. Scientists have invented many ways to see things, including cameras and spectrometers. Cameras have developed over the past few decades from simple analog black and white photography to ultra high definition colored photography. Spectrometers can also see things, but in a very different way than cameras. Spectrometers have also developed rapidly over the decades. Where cameras can see things visibly, spectrometers can determine the make-up of any object. Spectrometers can determine something as simple as biotic versus abiotic material, to the isotopic ratios of the mineral content of a rock on Mars. The use of spectrometers on spacecraft have added significantly to our knowledge of stars, planets, and natural satellites. Mars is the planet most visited by spacecraft that happen to include cameras and spectrometers. It is no surprise that the things we can see on Mars have come clearer, due to technological advancement, over the 50+ years we have been visiting the Red Planet. For centuries humans have speculated about Mars and its habitability, with habitability comes water. The fleet of spacecraft that have visited Mars had a particular interest in finding out if water has ever or does now exist.
In the 1960’s NASA sent two flyby’s past the planet Mars. Both of these spacecraft had what would now be considered primitive technology. In 1965, NASA’s Mariner 4 spacecraft flew by Mars and sent images back to Earth. The images were taken with what is described as a television camera mounted on the spacecraft along with a Cassegrain telescope and a vidicon tube that to translate the images. Scientists received the signal and had 22 small, black and white, crude images of the rocky and barren surface of Mars.(NASATech) The technology of the time was limited and, though the mission was a success, the information gleaned was hampered by this. In 1969 the Mariner 6 and 7 flew by Mars taking hundreds of pictures and other data and sending them back to Earth. These were nearly identical spacecraft with a television camera and an IR and UV spectrometer. The cameras imaged approximately 20% of the surface of the planet but did not image the 4 large volcanoes or Valles Marineris. The spacecraft confirmed the canali, previously predicted by Giovanni Schiaparelli in the late 19th Century, on Mars were merely an optical illusion and misinterpretation of data from Earth based telescopes. (NASATech)
Image 1: Image taken from the Mariner 4 television camera. (NSSDC)
The Viking I and II missions by NASA were composed of two landers and two orbiters. The orbiters imaged the entire planet with two vidicon cameras and took scientific data readings with an infrared spectrometer, to seek and track water vapor in the atmosphere. The landers took images from the surface with two facsimile cameras and a gas chromatograph mass spectrometer. (NASANatl) The Viking Orbiters’ instrument, called the Mars Atmospheric Water Detector, detected upwards of approximately 100 microns of atmospheric H2O. (Geo) Atmospheric water is an important discovery in order to establish a baseline for a planetary water cycle. The Viking landers carried gas chromatograph mass spectrometers (GCMS) to look for signs of organic material in the Martian regolith. The GCMS analyzes a sample by warming it up and sensing the gases that come off the sample and then a detector determines the spectrum of the sample. This is how we can see the elemental and isotopic make-up of objects.
Rampart craters were photographed by the Viking orbiters vidicon cameras, developed in the 1950s. The cameras were high technology at the time, but compared to our ultra high definition cameras now, the technology is obsolete. (dePater & Lissauer)
Image 2: Mars from the Viking orbiter spacecraft, mosaic of 102 images. (NASAMars)
Mars Reconnaissance Orbiter
The Mars Reconnaissance Orbiter (MRO) entered the orbit of Mars in March 2006. The MRO also carried the High Resolution Imaging Experiment (HiRISE) camera, made by University of Arizona (UofA), which operates in visible to near infrared and has a resolution of about a meter. As of 2006, HiRISE had the best resolution of any camera sent to space. The HiRISE camera has imaged many Recurring Slope Lineae (RSL) on Mars. RSLs are briny water flows that were discovered on the slopes of craters during warm weather on Mars. (NASAjpl)
Image 3: Recurring Slope Lineae photographed by the HiRISE camera on MRO. (NASAMRO)
Spirit and Opportunity
The Mars Exploration Rovers (MER) Spirit and Opportunity landed on Mars a few weeks apart in January 2004. The Opportunity Rover landed near and explored Eagle Crater. Opportunity had a suite of cameras, including a panoramic camera (Pancam), a navigation camera (Navcam) and hazard cameras (Hazcam). The Pancam, made by ASU, has a resolution of 1mm per pixel and functions in the range of near IR to near UV. As images from the Pancam were processed and viewed by the geologists on the team, it was discovered that a vast field of small round nodules had been discovered. (NASAMER)
The team next used the Miniature Thermal Emission Spectrometer (Mini-TES), made by ASU and Raytheon Santa Barbara Remote Sensing (SBRS), to determine the make-up of the nodules. The Mini-TES is an IR spectrometer that is best utilized for looking at the mineral content of rocks. It can peer through the dusty coating on the rocks and make a determination of the content. The spectroscopic analysis revealed the concretions to be hematite and jarosite.(Science)
Spirit landed three weeks later in a dry lake bed and found evidence of past water in a rock named Humphrey. The MER team instructed the rover to examine Humphrey with the Rock Abrasion Tool (RAT) and then utilized the Mini-TES to determine that the crystalline structures inside Humphrey had been in contact with water. (NASAPress)
At Gusev Crater, Spirit examined a grouping of rocks, including a rock named Clovis. The team investigated Clovis utilizing the Mossbauer spectrometer, made by Johannes Gutenberg University, which examines objects using the absorption and emission of gamma rays. This revealed the presence of eight iron bearing minerals including goethite, which only forms in the presence of water. (AGU)
The Phoenix Lander landed near the north polar region on Mars in May 2008. (Phoenix) Notable images, taken by the Surface Stereo Imager (SSI), built by the UofA, included a vast panorama of polygon shaped regolith which were indicative of ices beneath the regolith. The SSI was a stereo camera with a higher resolution than that of Pathfinder. The Robotic Arm Camera, made by the Max Planck Institute and U of A, was designed to take close up and microscopic, to a scale of 23 μm/pixel, images in color. The SSI took an image of a block of a frozen white substance that was later identified as water ice. This was the first surface observation of water ice on Mars. (Chaisson & McMillan) The thrusters had blown away the regolith and revealed the ice. Its photos taken over a period of approximately 30 days, revealed globules on the landing struts of Phoenix. The globules grew and receded then eventually completely disappeared. They were found to be liquid water mixed with perchlorates by the Thermal and Evolved Gas Spectrometer (TEGA), made by UofA and University of Texas, Dallas. TEGA was a high temperature mass spectrometer. It heated samples to a temperature in order to collect the gas coming off the samples to analyze. (AGUPhoenix)
Image 4: Ice sublimation on Mars, taken by he Phoenix Lander. (NASAPhoenix)
Mars Science Laboratory Curiosity (MSL)
The Curiosity Rover landed on Mars in August 2012. A few days later it was announced by John Grotzinger, Project Scientist for MSL, that Curiosity had landed in an ancient riverbed that flowed vigorously with fresh water up to waist deep. Grotzinger explained the water was so pure, based on chemical analysis of the surrounding area, that a person could have scooped up the water and drank straight from the river. (NASAcuriosity) This discovery was made initially by the Mastcam of the area that showed what appear to be concretions of rocks that would have been arranged in the position by the flow of water over a long period of time. Another clue to the ancient riverbed was the rounded pebbles, imaged by the Mastcam, jutting out of the edge of the compacted rocks and pebbles. The rounded pebbles show that the water had to have persisted for a period of time long enough for rocks to tumble over each other and reshape them from their former jagged appearance. (NASANews) The Mastcam, built by Malin Space Science Systems, is a panoramic camera mounted on the mast with a resolution of 7.4 cm per pixel at a distance of 1 km. The eyes have individual resolutions of 150 to 450 μm to a distance of 1 km. One of the cameras has a lens that can see the landscape, in color or monochromatic, at a much farther distance than those of the MER camera systems. Mastcam has video capability with a high resolution at 10 frames per second and has an eight gigabyte memory which can store thousands of images for a period of time long enough for the rover to uplink the data to the orbiter, which then send the information to Earth. (NASAcuriosity) The Sample Analysis at Mars (SAM), a GCMS made at NASA’s Goddard Space Flight Center, was designed to identify specific organic compounds by separating the gases and sending them through a series of spectrometer parts which detect elements like carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur, the key elements for life, then to the next spectrometer to determine if water vapor is present. SAM has 74 small sample cups, including several for calibration. The sample sensitivity is less than one part per billion for organic compounds. The oven on SAM has the ability to heat the samples to 1000* C for analysis. (NASACuriosity) Later, SAM sampled the surface regolith and determined water made up about 2% of the sample. (NASANews)
Image 5: Jutting rock conglomeration in Gale Crate on Mars imaged by MSL’s Mastcam. (EarthSky)
Astronomy is the oldest science and started by visually observing objects, thousands of years ago, which is still incredibly important today. As technology has improved, images sent to Earth by various spacecraft had better resolution and scientific instruments have been able to gather more detailed information. Rovers, orbiters and landers have benefitted from the technological advancements in miniaturization of instruments, allowing more scientific equipment to be carried on each craft. The implementation of cameras on telescopes and spacecraft have added to our knowledge of astronomy in so many ways that it cannot be calculated. Spectrometers see inside of things, not like an X-ray, but at an elemental level. The technology of cameras and spectrometers has changed astronomy by verifying the presence of water on Mars after over a century of speculation.
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