The Observational History of Mars as a Pathway for a Human Mission

The Advancements In and Importance of the Observational History of Mars as a Pathway for a Human Mission

Including current spacecraft in orbit and on planet

Abstract

A human mission to Mars is seemingly imminent. Understanding the observational history of the Red Planet and the discoveries made will lay the groundwork for the future visitors and later settlers of Mars. The observational history of Mars from ancient cultures to the 21st century will be examined. Observations can be made in many ways with the rapid technological advancements of the late 20th and early 21st century. Included will be naked-eye observations, Earth-based primitive and advanced telescopes, space telescopes, flyby missions, robotic landers, and rovers, as observation is more than just seeing. We must gather as much information as possible in order to ensure the safest arrival, visit, and eventual settlement of Mars. Between Elon Musk and SpaceX to Robert Zubrin and the Mars Society, the plan is to set foot on Mars. Observation is the key to determining a clear path to whether a human mission to Mars is feasible.

Introduction

Ancient civilizations observed Mars with the naked eye and wondered at its peculiar path through the celestial sphere. The cultures of the time made Mars part of their lore and sometimes religious deities were assigned to Mars such as the Greek God of War. The Red Planet has been the source of many mythologies over the millennia which pushed the astronomers of the 17th century to turn the newly invented telescope toward the red, glowing beacon in the sky as it was the source of many questions that longed to be answered. Scientific discoveries on Mars started with the very first telescopic observations by Galileo. No sooner than that was a science fiction and proposed science “facts” presented in artistic renderings.

Primitive telescopes of the 17th and 18th centuries became more advanced as improvements in lens development were made through the 19th and into the 20th century. The second half of the 20th century brought technological leaps that allowed astronomers to observe Mars with unprecedented detail. These advancements have allowed scientists to discover what is needed for a human mission to Mars through more detailed observations, not only with optical telescopes but with the full electromagnetic spectrum observing the surface and spectrometers delving into the geology of the planet.

Mars is the best option for a human mission. The fleet of spacecraft that have visited the Red Planet have observed and reported many similarities. Earth and Mars have a rocky surface that includes the same types of rocks and minerals, a 23 hour (h) and 56 minute(m) and 24h 37m solar days respectively, the axial tilt of Earth are 23.5o and Mars’ axial tilt is 25.19o which allow for seasons to occur, volcanic activity (dormant on Mars), hydrothermal vents past and/or present, water (salty, fresh, briny), regolith that is acidic and/or basic, magnetic fields (Mars has pockets of magnetic fields), and quakes.

Data from the Red Planet has been collected over decades and many human missions to Mars have been proposed. A prominent human mission was proposed by Werner von Braun after World War II. This project was outlined in his book, Das Marsprojekt, published in 1952. Although Von Braun’s mission never came to fruition, several missions are still being planned. Major plans for a human mission to Mars are being proposed by private and non-profit organizations. Observation of the planet Mars over the last several decades will allow us to determine the viability of a human mission to Mars. Scientists have been working diligently through various forms of observation to overcome any major risk factors such as extant life as a potential pathogen, radiation, water or lack of, and dust storms. Observation is the key to solving these issues for the next step of human exploration and settlement of Mars. Other risk factors, like the psychological effects of long-duration spaceflight, prolonged weightlessness, the potential failure of life support systems and spacecraft can be assessed through different methods. Throughout humanity, we have taken risks and sacrificed lives to expand our reach on Earth. A human mission to Mars is hypothesis-driven, critical thinking at its finest. We have it in our power to do something that will set humanity on a path that is bright and wonderful. It is our duty to send humans to Mars to become a multi-planetary species.

Ancient History of Mars Observation

Ancient cultures made careful observations of celestial objects and many cultures kept accurate records. The astronomical observation was essential for agrarian cultures in order to plant and sow crops. The five planets observed and recorded by ancient cultures included Mars. The initial observations of Mars were primitive and merely included facts as simple as the ruddy color of the object and the path through the sky over time, that varied from the background stars.

Ancient Chinese astronomers kept impeccable records of astronomical bodies and events. Mars was observed and recorded by Chinese astronomers before 1045 BC. Occultations and planetary conjunctions were observed and recorded in 368 CE, 375 CE, 405 CE. Because of the regular observations of Mars, by the time of the Tang Dynasty in 618 CE, the periodicity and orbit of Mars were known. (Ciyuan 1988)

The Babylonian culture made astronomical observations as early as 400 BC. They observed Mars, who they deemed the God Nergal, over long periods, enough to determine the object made 42 trips, or 37 synodic periods, through the zodiac every 79 years. The Babylonians had divided the zodiac into 12 equal parts of the celestial sphere. (North). Ancient Greek astronomers referred to Mars as Ares, the God of War. They also tracked the motions of the planetes across the sky. The Greeks used the term planetes because it meant wanderer, and the planet Mars and others visible to the naked eye seemingly wandered in a manner different than the other objects observed. They subscribed to the geocentric, Earth-centered, view of solar system bodies. (Air&Space) On 4 May 354 BC, the Greek philosopher Aristotle observed an occultation of Mars by the Moon, from this observation he determined that Mars is further from Earth than the Moon. (Lloyd) Greek astronomer Hipparchus expanded on the orbital path of Mars and the other wanderers and described the orbits in epicycles, small circles, and deferents, larger circles. (Kolb & Kolb 1996) This complex description was part of the geocentric model of the solar system which was later proven to be incorrect and replaced by what we now know as the heliocentric, or Sun-centered solar system. In the 2nd Century CE, the Egyptian-born Claudius Ptolemy, made many observations of Mars, trying to work out why the orbital period was faster on one side of the orbit than the other. He made adjustments to the orbital period to account for the difference. He published his findings in the Almagest, which stood as an accurate astronomical document for 14 centuries. (Linton)

Sometime between the 12th and 14th Centuries, the Mayan culture assembled the Dresden Codex. These are writings of the indigenous people of the Yucatan, Peninsula in Mexico, who were isolated from the aforementioned writings and data. The Mayans had a complex society and culture which included astronomical observations of Mars and other celestial bodies. With primitive technology, the Mayans observed Mars and determined the synodic and sidereal periods of the planet. (Bricker 1998)

The ancient observations of Mars inspired humans to dream and imagine what it was like in that world. Even before Galileo’s first telescopic observations of the Red Planet, humans wondered about the possibilities and exploration of other worlds.

The Advent of the Telescope Changed Our View of Mars

Galileo is given credit for inventing the telescope in the early 17th century. He observed many astronomical objects with his refracting telescope, including Mars. Galileo’s telescopes included a convex objective lens and an eyepiece that was a concave shape. Initially, he only achieved 8x magnification, however, he eventually achieved 20x magnification. He could not determine whether the Red Planet had any surface features, but he noted that it was not spherical at the time of his observations. (Snyder) In the mid-17th century, Christian Huygens observed Mars with a 37-meter (m) open-air refracting telescope without a tube to enclose the lenses. Although the telescope did not work well, he eventually made detailed sketches that include what is now known as Syrtis Major. He also concluded Mars had a rotation period of 24h. A few years later, Giovanni Cassini, working at the Paris Observatory, made more detailed observations. Cassini noted the rotation period was 24h and 40m, closer to the modern known sidereal rotation period of 24h and 37m 22 seconds(s), known as sol, or Martian day. Cassini also noted white areas on the north and south polar regions, which were thought to be snow and ice. Following up on Cassini’s observations in the early 18th century, his nephew Giacomo Filippo Maraldi, using a 10.34m refractor, observed the changes in the polar ice caps over time, determining Mars had seasons similar to Earth’s. He also noted surface changes, concluding they were clouds, but the observation was most likely dust storms. In the late 18th century, William Herschel continued the studies of Cassini and Maraldi. Herschel cast and polished his own lenses and mirrors for his reflecting telescopes. He believed the maria (Latin for seas) on Mars were filled with water, as had others previously. Herschel confirmed Mars had seasons based on his observations of the axial tilt and changes on the surface features. He attributed these changes to what he assumed were floods occurring when the maria overflowed during a wetter season. (Snyder)

• Image 1: Sketches by Giovanni Schiaparelli and Percival Lowell made in the 19^th century through telescopic observations. (Todd 1897)
  

During the latter half of the 19th century, Asaph Hall utilized the 66cm refractor at the US Naval Observatory in Washington DC for his observations of Mars. Hall was certain he would discover satellites around the Red Planet, and he would manipulate the eyepiece in order to reduce the glare of Mars and enhance the field of view surrounding the planet. In what he initially described as a “star near Mars” he had in fact discovered the two natural satellites of Mars, Phobos, and Deimos in 1877. (Snyder)

Giovanni Schiaparelli detailed his observations (See Image 1) of Mars in 1877 using a 218mm Merz refractor telescope, built by German maker Georg Merz. Schiaparelli meticulously charted every part of the Martian surface as he peered through his primitive telescope. The drawings were published, and the public became very interested in the canali he discovered. Schiaparelli’s grooves were misinterpreted into canals. A groove was meant to be a naturally occurring feature on a planet, but the misinterpretation from Italian to English proved to cause a frenzy across the astronomical world. Newspapers stated the features were canals, indicating an intelligent origin of the features. This misinterpretation caused much speculation and gave science fiction writers a new world to explore in the literature of the time. Schiaparelli’s discoveries inspired astronomers to do further observations. (Washam)

By 1894, Percival Lowell had established the Lowell Observatory in Flagstaff, Az. (See Image 2) The observatory was built by Lowell specifically to observe Mars and follow-up on the canali described by Schiaparelli and included a 61cm commissioned Alvan Clark refractor. Over 15 years of observation and recording data, Lowell also observed features that he thought to be intelligently designed. Some astronomers ostracized Lowell for his apparent discoveries. As telescopes improved, some of the naturally occurring channel features on the Red Planet were confirmed, others were found to be optical illusions. (Kidger) After years of observations, in 1906, Lowell published his controversial book, Mars and its Canals. This publication was met with a counter-publication by a biologist, Alfred Russel Wallace, who insisted Mars was uninhabitable due to his calculations of the surface temperature of -35oF (-37.22oC). (Snyder) Lowell’s ideas made him an outcast among many scientists, but he persisted and continued his observations and giving lectures.

Image 2: Percival Lowell making observations at the Lowell Observatory in 1914. (Lowell)

Gerard Kuiper utilized near-infrared (IR) spectroscopy to observe stars and planets. Kuiper used the first modern equipment to determine the atmosphere of Mars was made up mostly of CO2 in 1947. (NASA Science) This discovery arguably helped pave the way for technological advancements to observe Mars and allowed for further studies in order to plan for a human mission to Mars.

Modern Exploration begins with Mariner

Image 3: Image is taken from the Mariner 4 television camera. (NSSDC)

Image 4: Mars and Valles Marineris from the Viking orbiter spacecraft, a mosaic of 102 images. (NASAMars)

In the 1960’s NASA sent two flyby missions to Mars. Both spacecraft had what at times was the highest quality camera equipment but would now be considered obsolete technology. NASA’s Mariner 4 flew by Mars in 1965 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 to translate the images. The crude images received by the control center took hours to download from the spacecraft. 22 small, grainy, black, and white images were eventually printed and examined. (See image 3) The images of the rocky and barren surface of Mars were a disappointment to those hoping to find a thriving civilization on the Red Planet. (NASATech) The mission was considered a success; however, the limited technology available at the time inspired scientists to implement missions with more updated technology. Mariner 6 and 7 flew by Mars in 1969. The spacecraft took hundreds of pictures and other data. These were nearly identical spacecraft with a television camera and an IR and ultraviolet (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 observed by Giovanni Schiaparelli in the late 19th century, on Mars were merely an optical illusion and misinterpretation of data from Earth-based telescopes. (NASATech)

In 1969 Mariner 9 was the first orbiter to arrive at and orbit another planet. Observational instruments included a UV spectrometer, an IR spectrometer, and a visual imaging system with a resolution of 98m per pixel. This was a vast improvement from the previous spacecraft which had a resolution of 790m per pixel. Mariner 9 observed a global dust storm which was a surprise to the Mariner team. The imaging system could not readily peer through the dust and the team decided to delay most of the imaging for a couple of months as the dust settled. The dust storm was a disappointment at the time; however, it was an important discovery when considering landing spacecraft on the surface and for future human missions to Mars. Once the atmosphere started to clear, the imaging systems observed riverbeds, the volcanoes of the Tharsis Buldge including Olympus Mons, the largest shield volcano in the solar system, Valles Marineris (Image 4), and evidence of weather patterns and erosion. The orbiter also imaged the satellites of Mars, Phobos, and Deimos. Mariner 9 worked in orbit for 349 days, sending 7,329 images to Earth which covered 85% of the surface. (JPLMariner)

Technological Improvements and Detecting Life?-Viking I and II

The Viking I and II missions by NASA were composed of two landers and two orbiters and arrived at Mars in 1976. In a little over a decade, the observational technology improved greatly. Cameras see the surface of objects and are important observational tools, however, spectrometers were a boon to observational astronomy because they can peer beneath the surface of an object. Spectrometers allow for observation at a deeper level, seeing things at an elemental, molecular, and isotopic level. This allows scientists to see things that cannot be detected with the naked eye, including the make-up of the regolith and rocks on the Red Planet. The orbiters imaged the entire planet with two vidicon cameras (See Image 5) and data was collected from an IR spectrometer. The orbiters utilized the vidicon cameras to photograph rampart craters and a network of what are analogous to river drainage networks on Earth. (dePater & Lissauer) The IR spectrometer, called the Mars Atmospheric Water Detector, observed approximately 100μm of H2O in the atmosphere. (Geo) Detecting water in the atmosphere is extremely important in order to establish a baseline for a planetary water cycle.

Image 5: The north polar icecap of Mars taken by the Viking I orbiter, including the Mare Boreum Region and surrounding plains. A spiral feature in the water ice and layered regolith is prominent. (NASA/JPL/USGS)

The Viking I and II landers utilized observational techniques via two facsimile cameras, taking images of the surface, and a gas chromatograph-mass spectrometer (GCMS) for detection of minerals and possibly water. The landers carried GCMS’s to look for signs of organic material in the Martian regolith. The GCMS analyzes samples of regolith by heating it to a specific temperature for the particular sample and using sensors to detect what gases come off the sample and next the spectrometer determines the content of the sample. (NASANatl)

A limiting factor, that would need mitigation, to a human mission to Mars is the detection of pathogenic life. Viking I and II Landers each carried three life detection experiments with varying degrees of sensitivity, the Labelled Release Experiment (LR), the Gas Exchange (GEX), and the Pyrolytic Release Experiment (PR). Dr. Gil Levin invented the LR to investigate whether microbial life existed in the Martian regolith. The landers were approximately 6,400 km away from each other on the surface of Mars and both carried the LR. The LR worked by scooping up a sample of Martian regolith and sending it into a small tube, then a nutrient labeled with radioactive 14C was added to the sample. If microorganisms are present in the sample, they will consume the nutrient and then give off radioactive gas. Viking I and II both ran the LR experiment. When the experiment was performed, the nutrient was added to the regolith, and once processed, a spike was seen on the graph indicative of a positive result for life. The LR released a gas that persisted for a full seven days while the experiment was run. NASA developed a control experiment to verify whether the results were chemical or biological. The result of the control was negative. Chemistry is not living; therefore, it cannot die from an experiment, but biology can. Levin and other scientists ascertained life exists on Mars based on the negative control and positive LR experiment. Levin insists life exists on Mars according to the criteria set by the Viking team at NASA. (See Figure 1) During the course of the investigations, Viking I and II both had a positive result for life with the LR experiment.

Figure 1: Labeled Release Experiment Data from Viking I indicating the cycle 2 control versus the active cycle 1 and 3. (Levin)

The GEX and PR failed to detect life in the soils of Mars. Because two out of the three experiments tested negative, NASA made a consensus that there was no life on the Red Planet. The decision was based on the chance that these results may have been chemical organic reactions. Levin insists the LR tested positive for life due to the increased sensitivity compared to the GEX and PR. The sensitivity of the LR was able to detect 1/1 x 106 cells in the soil, while the others were orders of magnitude less sensitive which easily explains why they were negative versus the positive results of the LR. (Levin) Subsequent rovers and the Phoenix lander detected perchlorate in the regolith on Mars. According to the team at NASA, the process of heating a sample with perchlorate would destroy any chance of detecting organics, thus the negative results on GEX and PR. (Clarke) The scientific method is clear that results should be reviewed and retested. Therefore, if one out of three tests is positive, in order to follow protocols of the scientific method you must rerun the experiment multiple times, preferably with improved technology and instrument sensitivity, to get an accurate result. (Levin) NASA has not landed any other life detection experiments to Mars since Viking I and II, they have sent experiments to detect biosignatures. The Mars Perseverance Rover, slated to land on Mars in February 2021, does include life detection equipment. Finding a definitive answer to whether life exists on Mars is essential to determine in planning a human mission.

Low-Earth Orbit Observations

The Hubble Space Telescope (HST) went into low-Earth orbit in 1990 and has been repaired several times. HST is a Ritchey-Chretien Reflector with a 2.4m diameter and a focal length of 57.6m. The telescope utilized the near IR, visible, and UV spectrum for observations. Hubble has taken the highest resolution images of Mars from Earth orbit of any other optical telescope. HST is able to image an entire hemisphere of the Red Planet and those images can be studied by scientists to track weather systems, which will aid in allowing humans to predict dust storms as they approach and eventually land on the surface of Mars. Martian weather can be volatile very quickly and these observations are essential for climate modeling on Mars. (James 1993)

The Chandra X-ray Observatory is a 1.2m Wolter type 1 X-ray telescope with a focal length of 10m and a resolution of 0.5 arcseconds. Chandra has observed X-rays from 2001-2003 being emitted from Mars. Two types of X-ray sources were discovered, one source was from solar particles being scattered off of the upper atmosphere and the second source was from an exchange of ionic charges. (Dennerl 2002) Sources of X-rays are important observations to make in order to prepare for a human mission to Mars. X-rays are known to cause cancer in humans and other organisms due to the harmful radiation exposure interrupting the cell cycle and causing cells to continue dividing. More studies are needed to determine the potential risk to humans.

Radiation is Dangerous and Needs Mitigation

Earth provides a protective cocoon for organisms through the magnetosphere and the atmosphere. The magnetosphere is the first line of defense from harmful solar particles and the atmosphere is the next defense via deflection of radiation. (Saganti 2010) Humans on Earth receive about one millisievert (mSv) of radiation per year. A sievert is a unit of ionizing radiation that includes the health impact on a human as it is deposited in tissue.

Mars Odyssey went into orbit in 2001. The spacecraft carries the Mars Radiation Environment Experiment (MARIE). The instrument found that astronauts in orbit around Mars would encounter two and half times more radiation exposure than at the ISS. Based on these observations, astronauts orbiting Mars would encounter limits higher than those put in place by NASA. (Cucinotta & Cacao) However, the most reasonable human to Mars plans includes a landing party, not merely an orbital crew.

Humans have been going into space for six decades. More recently, humans have spent 6 months or more at a time at the International Space Station (ISS). On the ISS humans encounter a 150% increase in radiation than on Earth. We have decades of data and scientific studies have shown that each part of the human body reacts differently to being in space. Radiation can have profound effects on humans in space, including cancer. The Multilateral Human Research Panel for Exploration has compiled data and determined that radiation is one of the most concerning health risks for a human mission to Mars.

Figure 2: Human radiation exposure in space in mSv from the Gemini missions in the 1960’s, through the Moon missions, and the International Space Station, including estimates for a future human mission to Mars and the satellite of the outer Solar System, Callisto. (Baatout 2020)

Earth radiation is shielded much more than open space radiation without shielding or exposure to radiation on the surface of Mars. A human mission to Mars will increase radiation exposure by up to 1000%. (See Figure 2) The amount of radiation a human may encounter depends on the mission, the spacecraft, the destination, the duration, the conditions of the Sun, and the habitat on the planet. Mars has a very weak magnetosphere and a very thin atmosphere; both provide little protection from radiation. A human mission to Mars will likely include a six-month space journey to the Red Planet and up to an 18-month stay on the surface and a six-month return journey. Three major categories of radiation exposure include: the solar wind, solar particle events, and galactic cosmic rays. The solar wind includes low-energy particles electrons, protons, and alpha particles, solar particle events include high-energy protons, and galactic cosmic rays are 87% high energy protons and 12% alpha particles, heavy ions of Fe. (Baatout 2020) The amount of radiation the astronauts would be exposed to en route would be ~660mSv and if the crew is on the planet for about 500 days, the crew will be exposed to ~275mSv for a total exposure of ~935mSv for the duration of the journey. Based on calculations of on Earth exposure to radiation, this increases a human’s chance of getting cancer by 5%. (JPL)

Radiation research and mitigation need to continue in order to ensure safe transport to and from Mars for humans. More data needs to be collected to determine the precise risk. Exposure to harmful radiation can be reduced by building human habitats underground in a cave or lava tube to protect them from exposure on the surface of Mars. The spacecraft could be designed to use water as a protective shield from solar and galactic radiation while en route to Mars.

Testing New Technology and Making Discoveries-Pathfinder-Sojourner Rover

On July 4, 1997, after two decades without a spacecraft on the surface, the two-part spacecraft Pathfinder Lander and Sojourner Rover, landed on Mars. Sojourner was the first rover deployed on another planet. She was a solar-powered rover about a meter in length with a planned 30- day mission that sent observational data to Earth for 83 sols. The observations included finding evidence of previous volcanic activity in the form of basaltic rock, which is known to increase fertility in soils. This is a useful observation for a human mission to Mars, in order for explorers to utilize the volcanic ash and utilize for fertilizer in greenhouses. An X-ray spectrometer onboard determined the regolith contained evidence of a warmer and wetter past and the optical instruments observed rounded pebbles at the landing site. Rounded pebbles are indicative of flowing water over time which tumbles the rocks and metamorphosing the jagged edges into a smooth round pebble. (NASAPS) Optical observations from the Pathfinder Lander were made with a stereo imager with a height of 1m above the surface. The Imager for Mars Pathfinder (IMP) observed an area with a volume of hundreds of km2 of ancient catastrophic flooding. Applying Earth analogues as evidence, the team of geologists stated the area of stacked sharp and rounded rocks were also indicative of catastrophic flooding. (NASAGeo) Thus began the subsequent “follow the water” missions by NASA. Water on Earth is a good indicator of life. One of the most important areas of research in preparation for a human mission to Mars has been determining if extant life exists. Discovering water is the main objective in ascertaining the habitability of Mars and is the key to discovering extant life on Mars.

The Twin Mars Exploration Rovers Follow the Water-Spirit and Opportunity

In January 2004, the Mars Exploration Rovers (MER) Spirit and Opportunity landed on Mars a few weeks apart. The twin rovers were equipped with many cameras and spectrometers in order to observe and study the Red Planet and “follow the water,” as stated by Dr. Steve Squyres, Principal Investigator, MER. Following the evidence for water on Mars is important for two major reasons: water is necessary for human consumption and water as a solvent is necessary for the evolution and development of life forms as we recognize them.

The Opportunity Rover landed near and explored Eagle Crater. Opportunity had a panoramic camera (Pancam), a navigation camera (Navcam) and hazard cameras (Hazcam). The Pancam had a resolution of 1mm per pixel and functions in the range of near IR to near UV. As images from the Pancam were observed by the geologists on the team, a vast field of small round nodules had been discovered. (NASAMER) The MER team used the Miniature Thermal Emission Spectrometer (Mini-TES) to determine the make-up of the nodules. The Mini-TES is an IR spectrometer that was developed to determine the mineral content of rocks. The spectroscopic analysis revealed the concretions to be the minerals hematite and jarosite, both form in the presence of standing water over time. (Science)

Spirit landed in a dry lakebed of Gusev Crater and found evidence of past water in a volcanic rock named Humphrey. The rock had an unusual shape and veins of a crystalline structure. The MER team instructed the rover to observe and 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 over a period of time consistent with the crystalline formations observed. (NASAPress) Spirit also examined a rock outcrop named Clovis. The team investigated Clovis utilizing an alpha particle X-ray spectrometer and a Mossbauer spectrometer, which examines objects using the absorption and emission of gamma rays. This revealed the presence of eight iron-bearing minerals including goethite, which only form in the presence of water. (AGU)

Eyes in the Sky-Mars Reconnaissance Orbiter

Image 6: Recurring Slope Lineae photographed by the HiRISE camera on MRO. (NASAMRO)

The Mars Reconnaissance Orbiter (MRO) entered the orbit of Mars in March 2006. As the name indicates, it is a reconnaissance and observational mission. The MRO carried the High-Resolution Imaging Experiment (HiRISE) camera, which detects visible to near-infrared light and has a resolution of about a meter. As of 2006, HiRISE had the best resolution of any camera sent to space. NASA scientists serendipitously discovered that the HiRISE camera imaged what later became known as Recurring Slope Lineae (RSL) on Mars. (See Image 6) In 2015 NASA announced MRO had discovered hydrated minerals in the area of the RSLs. Similar to ice melting on Earth, scientists discovered the RSLs grow and recede with the temperature and seasonal changes. Also, the RSLs appear more commonly at mid-latitudes where the temperature is warmer. (NASA JPL) Studies revealed the RSLs appear more often as Mars’ axial tilt aims the areas toward the Sun and the temperature reaches -23o C. Water that contains perchlorates and other minerals, dubbed hydrated salts or briny water, can exist below the freezing point and at the observed temperature and pressure on Mars. (McEwan 2013) After many studies and observations, RSLs were theorized to be briny water on the slopes of craters during periods of relatively warm weather on Mars. (NASA JPL) Extreme organisms called halophiles are known to survive in briny salts on Earth. It is imperative to make observations and search for water which leads to the search for life forms on Mars. Finding organisms and sequencing their genetic material to determine if they may be detrimental to humans who plan to visit and later settle the Red Planet is a necessary goal. However, scientists may find this discovery is only possible once humans reach the surface of Mars.

A diametrically opposed view proposed by other scientists is water is not the cause at all but instead, blocks of carbon dioxide (CO2) ice moving down the slopes are causing the linear gullies. The theory states as the season's change, blocks of CO2 ice are loosened by sublimation. Blocks of CO2 ice then fall down the steep slopes carving gullies that appear to be evidence of flowing water. (Dinega 2013). Both proposals are equally important when considering a human mission to Mars, as we must be prepared for either scenario. “Since the 1990’s debunkers have said liquid CO2 or rivers of sand were the cause of the channels on Mars. People are trying to come up with theories and ignoring the most obvious, these channels were created by transient water on the surface of Mars.” (Zubrin)

The North Polar Region and the Phoenix Lander Discovers Water Ice

In May 2008 the Phoenix Lander landed in the north polar region of Mars. Notable observational images were taken by the Surface Stereo Imager (SSI). SSI stood 2m above the surface of the planet. It was manufactured with a resolution to simulate the eyesight of a human. The 1024x1024 pixel images produced were high density and the camera used 12 wavelengths from optical to IR. The SSI imaged a vast panorama of polygon-shaped regolith. When ices freeze and thaw with regolith or other debris atop, they tend to crack in polygon shapes which lead to the debris falling in between each polygonal-shaped ice formation. The Phoenix observations were indicative of ices beneath the regolith. (Phoenix)

The landing thrusters on Phoenix had blown away regolith which 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) Further observation of photos taken over a period of approximately 30 days, revealed globules on the landing struts of Phoenix. Scientists carefully observed the globules, which grew and receded then eventually completely disappeared. This unexpected discovery was examined by the Thermal and Evolved Gas Analyzer (TEGA) and found to be liquid water mixed with perchlorates. TEGA is a high-temperature mass spectrometer that heated samples in order to collect the gas coming off the samples to analyze. (Keller 2008)

Bigger, Better, and Bursting with Scientific Equipment-Mars Science Laboratory Curiosity

The Curiosity Rover landed on Mars in August 2012. Soon after, 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. Further observation and study by the MSL team indicated 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. (Grotzinger 2013) The observation was made by Mastcam, a panoramic camera mounted on the mast with a resolution of 7.4cm per pixel at a distance of 1km, of an area in Gale Crater in which have been observed 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. More observations revealed rounded pebbles jutting out of the edge of the concretions. (See Image 7) The rounded pebbles indicate 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. (Grotzinger 2013) Observations are consistent with water on Mars in the past assist scientists in determining habitability. This evidence proves pure liquid H2O existed or exists on Mars. The water may now be in reservoirs or lakes under the surface. Subsurface water could be extremely important for settlers of the Red Planet, as water is essential for survival.

Image 7: Jutting rock conglomeration in Gale Crater on Mars imaged by MSL’s Mastcam. (NASA)

Observation and discovery of organic compounds are essential to prepare for a human mission to Mars. Organic compounds can be used for a variety of things, including making rocket fuel for a return mission, nutrients for agriculture, determining habitability, etc. Curiosity carried Sample Analysis at Mars (SAM) which was designed to identify specific organic compounds by separating the gases and sending them through a series of spectrometer subdivisions. Each subdivision could detect elements like carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur (CHNOPS), the key elements for life. The sample is eventually sent to a spectrometer to determine if water vapor is present. The oven on SAM has the ability to heat the samples to 1000^oC for analysis. SAM is made up of three instruments, including, a quadrupole mass spectrometer, a gas chromatograph, and a tunable laser spectrometer. Together they take very precise measurements of carbon isotopes and oxygen. The ratios of these elements help determine the amount of CO2 and methane (CH4) in the regolith and the atmosphere. SAM can also determine the amount of H2Oin a sample utilizing the tunable laser spectrometer. SAM sampled the surface and determined water, essential for all biological organisms, made up about 2% of the Martian regolith. (NAT, Grotzinger 2013) Specific ratios between CO2 and CH4 help scientists determine whether the molecules have a biological or geological origin. Resolving the percentages of the ratios of these molecules is essential for determining the feasibility of a human mission to Mars. “[A] striking aspect of the Curiosity discovery is that the concentration of methane detected varies sharply over time. That can only be the case if the source of the methane is locally concentrated, as a globally spread source could not cause such sharp variations. Thus, there may be a patch of ground relatively close to Curiosity which is the source of the emissions, and, therefore, a prime target to drill in an attempt to find subsurface life. Similar biologically suspect spots may well exist elsewhere. We need to locate such spots, and then send human explorers to drill and find out what lies beneath,” states Dr. Robert Zubrin, President of the Mars Society. (Zubrin 2020)

Observations made by Curiosity show the area not only includes a dry riverbed but also elements and molecules which include, biologically usable N, CH4, and all other elements and minerals needed for life to exist and the regolith is conducive to growing crops. The atmosphere is made up of mostly CO2, which is the molecule plants utilize for photosynthesis. In a study conducted at Embry riddle Aeronautical University they studied the observations from the past rovers and landers to determine the pH of the regolith on Mars varies from slightly acidic pH of 5-6 and later observations determined the pH is alkaline from ranging from 7.2 up to 8.3, macronutrients O, C, H, N, P, K, Ca, Mg, and S, and micronutrients Fe, Zn, Cu, Mo, Mn, B, Cl. The regolith is also loosely packed and porous enough to support root structures which is essential for plant sustainability. (Embry-Riddle) The regolith contains perchlorate which would damage plants, but it can be separated in-situ and the remainder of the regolith can be used for planting crops. These studies and others like them indicate humans will be able to utilize the Martian regolith in a greenhouse to grow crops for human consumption and generate oxygen for human respiration.

Astonishing Discoveries Made with Meteorites from Mars

Martian meteorites fall to Earth at an estimated rate of approximately 450kg a year. Scientists have over 100kg of meteorites from Mars in labs across the world. (Weiss 2020) These extraterrestrial geological samples are the only rocks from Mars we have to examine until a sample return mission, or a human mission occurs. Studying Martian meteorites is important for planning a human mission to Mars to give insight to what is or has been present on Mars. This includes whether water, organic material, or fossilized remains are contained in the meteorites. These observations may help to determine whether life exists or has existed on Mars in order to protect future explorers.

Image 8: Meteorite ALH84001. Insert: SEM image of the bacterium claimed by Dr. David McKay’s team. (NASA)

A meteorite dubbed NWA 7034 was discovered in the Sahara Desert in Africa in 2011. After chemical analysis and another testing, NWA 7034 was found to be a 2.1 billion-year-old volcanic meteorite from Mars. The rock was given the nickname “Black Beauty” because of its beautiful dark sheen. NWA 7034 gave off much more water vapor during testing than previous Marian meteorites. Studies concluded Black Beauty had been altered by surface water during its time on the surface of Mars. According to NASA scientists, NWA 7034 is the richest geochemical meteorite found to date. (ISMP NWA 7034 2013)

The Nakhla meteorite fell in Egypt in 1911. It was later determined to be a Martian meteorite that had been in an aqueous environment. In 1998-1999, a scientific inquiry into the rock was performed by a team from NASA. After several interesting finds utilizing optical microscopes and scanning electron microscopes (SEM) for observation, it was determined that Nakhla contained the amino acids aspartic acid, glutamic acid, glycine, alanine, and y-aminobutyric acid. It is unclear if these amino acids originated on Mars or were the result of terrestrial contamination. However, the meteorite was an observed fall, and pieces were recovered within hours in some cases. The aforementioned amino acids were taken from a slice of the interior of one of the samples, (Glavin 1999) thus the odds of contamination are lower than that of a meteorite that has been on the surface of Earth for an unknown period of time being exposed to the elements and organic materials. Amino acids code for a three-part grouping of nucleotide base pairs which make up proteins that encode genes which then make up a DNA strand. This discovery and others like it can only be confirmed by a non-contaminated sample-return mission or by a non-contaminated human mission to Mars, both scenarios have problems that need a plan for resolution.

Meteorite ALH 84001 was discovered in 1984 in a region of Antarctica called Allen Hills. The Allen Hills meteorite was being studied by Dr. David McKay and a team of scientists at NASA. In 1996 McKay published an article in the Journal Science that claimed meteorite ALH 84001 had microfossils inside of it. (See Image 8) Using a scanning electron microscope (SEM), McKay and his team imaged very fine slices of the meteorite. D. McKay and his team determined ALH84001 contained microfossils of bacteria that had been preserved in the meteorite from Mars. The team concluded life had once existed on the Red Planet (McKay, et. al. 1996) which brought up the issue of extant, or current, life on Mars. Following the scientific method, other scientists examined the evidence. Some scientists came to the conclusion that the results were an artifact of the SEM process and not life. Other scientists stated based on the minute size of the ‘fossil’ it was too small to be a bacterium. They received pushback from another group proving they had found bacteria even smaller than the ALH84001 ‘fossil’ here on Earth. The fossilized bacteria claimed to be found by D. McKay and his team has not been conclusively verified. Dr. Chris McKay stated ALH84001 was volcanic rock and not a likely candidate for biological fossils. (McKay, C.P.) ALH84001 will continue to be studied by scientists. The only way to determine the validity of D. McKay’s results would be for a sample return mission or a human mission to discover similar bacteria.

Regardless of the status of fossilized bacteria in ALH84001, Dr. Chris McKay states the water present on Mars leads to the conclusion that extant life is possible on Mars. We have proven liquid water exists on Mars, for short periods of time under the correct circumstances. McKay explains that the surface of Mars has conditions that may be too harsh for life, but the conditions just beneath the surface of the Red Planet are conducive to extreme organisms as we see here on Earth. Also, the meteorites found on Earth that are from Mars, may give us a clue to whether there was a second genesis or if the seeds of life (amino acids) from Martian meteorites may have landed on Earth and allowed for life to occur on Earth. (McKay 2010)

Is Life on Mars a Show-Stopper?

Finding fossilized or extant life on Mars is extremely important to planning a human mission to Mars, as such a mission could be devastated by a bacterial pathogen. If that were the case humans would be left on Mars and unable to return to Earth. The question of whether Mars had conditions for life to arise and persist is essential to address. Fossilized life would indicate life could be abundant in the universe. Extant life would be examined and sequenced to determine if we are related to Mars life or if a second genesis occurred. Either discovery changes our understanding of the universe. Habitability is a key indicator of whether life could have arisen on Mars. The planet Mars has many prerequisites for life, as determined by the one example we have, Earth. To determine whether life exists on Mars, life must be defined. Astrobiologists study extremophiles, organisms that live under extreme conditions compared to humans, on Earth to determine the conditions life is able to persist in. Discoveries by astrobiologists over the last few decades have changed the parameters of how life is defined. Life on Earth depends on a magnetic field that shields life on our planet from being bombarded by harmful solar particles. Magnetic field pockets have been detected on Mars. The InSight Lander is detecting Marsquakes contemporaneously with this publication, potentially solidifying the presence of a more significant magnetic field than previous observations have indicated. (InSight) Observations have shown the mineral content of Mars includes the six elements that are found in all life forms on Earth, CHNOPS, including biologically available N. Nitrogen in the biologically active form is conducive to supporting organisms that we know eke out a living in the same type of environment on Earth. A more complete record of prebiotic chemistry needs to be determined as the minerals that exist in the regolith are not a sole indicator of life. Wherever liquid water exists on Earth, we find life in some form. Mars has water in liquid form that occasionally erupts from below the surface and persists for short periods of time as brine on the surface. A brine is a mixture of water and salts, like perchlorate, which allows water to exist in liquid form to exist in the cold temperature and low pressure on Mars. This indicates water is present in the subsurface of Mars. (McKay 2020) The presence of water does not verify the presence of life, however, every example of life on Earth depends on water to survive. Mars also possesses organic material, including CH4, which is commonly associated with biological processes. Methane on Earth is formed from biological sources 90% of the time. Yet, due to the possibility of serpentinization of minerals and geological cycling of methane, further research needs to be done to determine the biological or geological origin of CH4. (Astrobio)

These facts alone are not unequivocal proof of extant life on Mars, but together they make a compelling case. Further research needs to be conducted to prove extant life exists on Mars in order to mitigate potential hazards to a human mission. To help make that determination, three missions launched to Mars in 2020, NASA’s Mars Perseverance Rover, the United Arab Emirates Mars Mission orbiter, and China’s Tianwen-1 which included an orbiter, lander, and rover.

The Future-Mars Perseverance Rover to Search for Life and Lay the Groundwork for a Human Mission to Mars

The Perseverance Rover is scheduled to land on Mars on 18 February 2021 at a site called Jezero Crater. Perseverance has four major goals. The first goal is to determine whether life ever arose on Mars, the second goal is to characterize the climate of Mars, the third is to characterize the geology of Mars, fourth and most importantly to prepare for human exploration of Mars.

The main mission of Perseverance is to seek signs of ancient life on Mars. Jezero Crater was chosen because it once held a lake as indicated by its’ inflow channel, outflow channel, and preserved river delta imaged previously by orbiting spacecraft. The crater has diverse mineralogy that is an excellent site for searching for signs of ancient life. The turret and body of Perseverance are equipped with a variety of scientific instruments. This group of instruments, which include a UV spectrometer and an X-ray spectrometer, was purposefully designed to search for evidence of life.

Perseverance will collect rock samples and cache them for a possible return to Earth which will also be examined for signs of life. The rover has a percussive drill located on its robotic arm that will retrieve the geologic samples. The samples will be taken from a few centimeters below the Martian surface and stored in the caching system. Perseverance will collect approximately 20 samples with a size of 1.3 cm by 6 cm, leaving behind drill holes of 2.7 cm in diameter. The rock collection and caching system will be monitored by a camera called CacheCam, which will keep a photo record of each sample including how and where they were collected. NASA’s plan is to store the samples on the Red Planet until the cache will be retrieved and sent back to Earth. (NASAperseverance). The importance of which is to determine whether any bacteria found will harm and humans who travel to Mars and/or those with the hope of one day returning to Earth.

Another goal of Perseverance is to characterize the climate of Mars. Climate and weather information is extremely important to observe for future human explorers to be able to prepare for conditions they will encounter once on Mars. The Mars Environmental Dynamics Analyzer (MEDA) is a set of sensors that will provide measurements of pressure, temperature, wind speed, relative humidity, and wind direction. In order to plan well for a human mission, scientists must determine the size and shape of dust particles in the Martian atmosphere. MEDA will measure the size and shape of atmospheric dust particles in order to plan for proper filtration and ventilation systems for space suits and for habitats. Observations from the previous spacecraft on and orbiting Mars have helped scientists determine the dust on Mars can damage the articulated gears of robotic explorers and may also jam the articulated joints of spacesuits. This is an area needing further study in order to keep future Martian's safe once on the planet.

Several small samples of astronaut spacesuits will be housed inside the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument. It is important to study the samples of space suits to determine how the harsh Martian environment will affect the materials over time.

The Mars Oxygen ISRU Experiment (MOXIE) is a new instrument on Perseverance that’s purpose is directly associated with a human mission. Oxygen exists abundantly on Mars in the form of CO2. The MOXIE instrument will heat the CO2 to 800o C which separates the molecules into carbon and oxygen. If successful, the conversion of Martian CO2 into O2 will pave the way for a human mission to Mars via the ability to manufacture rocket fuel for a human return mission to Earth. The implications are also relevant to O2 generation for human life support systems. MOXIE is “an exploration technology investigation that will produce oxygen from Martian atmospheric carbon dioxide.” (NASAperseverance)

Conclusion

Astronomy is the oldest science and began in prehistoric times with Homo sapiens visually observing objects. Observation, either visually or with scientific instrumentation, is incredibly important today. Technological advancements have allowed for spacecraft to carry instruments with better resolution for visual observations as well as carrying scientific instruments such as spectrometers. Reconnaissance missions that have taken place over the last several decades have been able to gather more detailed information in order to determine whether a human mission to Mars is a realistic goal. Spacecraft such as telescopes in low Earth orbit, rovers, orbiters, and landers have benefitted from the technological advancements and miniaturization of instruments, allowing more scientific equipment to be carried on each craft. The implementation of cameras and spectrometers on spacecraft has added to our knowledge of Mars in ways that are incalculable.

A human mission to Mars is of vital importance to humanity. Mars is where the science is, where the challenge is, and it is where the future is. Mars was once a planet covered in water for a billion years. It took a fraction of that time for life to evolve on Earth, so if the “follow the water” theory is correct, Mars had or has life. If humans arrive on Mars and discover fossils, it will prove that life is the result of chemistry and water existing on a planetary body and that it is a general phenomenon in the universe, thus common. If we go to Mars and drill to the water beneath the surface and find organisms, we can examine the genetic structure. If the genetic material has a similar structure, we may be related to that life. If the genetic material is completely different or if we find an organism with genetic material that is unrecognizable, we may have found a second genesis of life in our own solar system. This would prove that life is abundant in the universe and can form in a variety of ways. Contrarily, if we go to Mars and find that it is devoid of life, that may prove that life is rare and even more precious and should be cared for greatly. The challenge for humans is the next major reason for a human mission to the Red Planet. Humans grow and develop in innumerable ways when faced with a challenge, but humans become stagnant when faced with routine devoid of future goals. The youth of the world would benefit enormously from a human mission to Mars. The students of today would be inspired to enter careers in engineering, aeronautics, mathematics, physics, astronomy, geology, etc. The intellectual capital from a venture of this type would be incalculable. This would create a culture of scientific literacy and curiosity the world has not seen since the Apollo missions. Millions of young people would be motivated to become explorers of a new world. Finally, the future of humanity is a stake. Mars is the closest planet with all of the resources needed for humans to inhabit. (Zubrin)

Throughout humanity, we have taken risks and sacrificed lives to expand our reach on Earth. Mars is the next step in human exploration and settlement. A human mission to Mars can be accomplished. Scientists have been working diligently through data collection and observation to overcome any major risk factors. The biggest hurdle to be overcome is whether the decision-makers have the will to go to Mars. “Virtually every element of significant interest to industry is known to exist on the Red Planet. With its twenty-four-hour day/night cycle and an atmosphere thick enough to shield its surface against solar flares, Mars is the only extraterrestrial planet that will readily allow large-scale greenhouses lit by natural sunlight. Mars can be settled. For our generation and many that will follow, Mars is the New World.” (Zubrin)

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