Extant Life on Mars
Vice Chair of Marspedia &
Education Director for RedPlanetPen.com
It is licensed under Creative Commons BY-SA 3.0 and may be freely shared, but must include this attribution.
Contents
Abstract
The habitability of Mars is the key to discovering extant life on Mars. The question of whether Mars had conditions for life to arise and persist will be explored. The planet Mars has a high probability of extant life due to the many prerequisites for life that exist on the planet, as determined by the one example we have, Earth. Further research needs to be conducted to prove extant life exists on Mars. Defining life is paramount to any discovery of biological organisms, this will be examined by comparing the fossil records of early life on Earth and the examples of extremophiles presently being studied. Magnetic field pockets have been detected on Mars, which is thought to be necessary for life forms to be protected from harmful solar particles. Marsquakes are being detected by the InSight lander, contemporaneously with this publication, potentially solidifying the presence of a magnetic field, however that alone does not determine the existence of life on Mars. (InSight) Minerals that exist in the regolith are not a sole indicator of life. The mineral content of Mars [CHNOPS], including biologically available N, 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. Amino acids, the building blocks of DNA, have been found in meteorites from Mars. Mars has water in liquid form that occasionally erupts from below the surface and persists for short periods of time as a brine on the surface, allowing the liquid form to exist in the cold temperature and low pressure. Water is present in the subsurface of Mars. (McKay 2020) The presence of water does not equate to life, but every example of life on Earth depends on water to survive. Mars has organic material, including methane, 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. My expected outcome is to display the high probability of extant life on Mars utilizing data collected by NASA, ESA and others over the last several decades.
Introduction
The description of what life is had eluded biologists for decades. The more we discover about extreme organisms on Earth, the more we question what life really is. In the past it was thought that all life on Earth needed three things, sunlight, a source of energy, and water. We now know that life persists in the depths of caves for thousands of years and in the isolated lakes of Antarctica for millennia, without sunlight. Discoveries of this kind have set in motion an entirely new science, astrobiology. Astrobiologists study extreme organisms on Earth to help them understand whether life can survive on another world. Over the past few decades, enormous amounts of data have been collected to support the supposition that life can exist on other worlds. It is very likely that life exists on Mars due to the overwhelming scientific evidence of conditions on the Red Planet, the variety of extreme organisms found on Earth, and the cometary amino acids and possible meteoritic microfossils.
In order to search for extant life on Mars, scientists need to explore the differences in the two worlds. Earth has an average temperature of 15o C whereas Mars has an average temperature of -60o C. The atmosphere of Earth is 100 times as dense as the Martian atmosphere and Earth has an atmosphere that is 20% O2 whereas Mars has trace amounts of O2 at best and is over 95% CO2. The Earth has a very strong magnetic field that protects life on Earth from harmful solar particles, however, Mars has a tenuous and spotty magnetic field that occurs only regionally. To find life on Mars scientists need to identify a source of nutrients, energy and water at the least. Mars is a hostile environment, any life on Mars would have to be able to tolerate high amounts of radiation, low nutrient availability, little liquid water, cold temperatures and toxic regolith.
Yet, many reasons exist for the search for life on Mars, including but not limited to, the scientists working on the missions get paid a salary and that money goes back into the economy, young students are inspired to explore scientific careers, and most importantly to prepare for a human mission to Mars. If extant life exists on the Red Planet, it is of extreme importance to have that information in order to protect people from potential pathogens.
What is Life?
In order to know whether life persists beyond Earth, we must describe what life is and differentiate between geochemical reactions and/or chemical reactions and what biology really is. Many extreme organisms have been found that push the traditional definition of life outward in every direction, which brings up many questions for consideration. What is a virus? It can reproduce, but it is considered not to be life because it must have a host to reproduce. Does size matter? Can something be too small to be alive? There are bacteria that are smaller than viruses. Can something be too big to be alive? Can organisms live in soil with a high or low pH? Are there energy gradients available for an organism to utilize the chemicals available for metabolism? What temperatures can life survive at? All of these questions must be addressed before scientists come up with a true definition for life. In order to come up with an agreed upon definition we must describe what elements are needed for life as we know it to exist. We must also decide whether or not water is necessary and in what state. A simple definition of life from dictionary.com states, “the condition that distinguishes organisms from inorganic objects and dead organisms, being manifested by growth through metabolism, reproduction, and the power of adaptation to environment through changes originating internally.” This definition may work for laymen but when it comes to the plethora of extreme organisms we are finding now and with the search for organisms on Mars we need a much more specific definition. It has been difficult to get scientists from around the globe to agree on one definition of life.
There are six required elements necessary for all life on Earth. Biologists use the term CHNOPS which are known to chemists as carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Prebiotic chemistry is the study of how complex molecules that might allow the “switch” to biology might have emerged without life. Models in prebiotic chemistry describe how these non-biological molecules might, under defined conditions, somehow become biological. The missing link is the ‘somehow become biological’. The first form of life was a single celled organism that required water for its biological processes. The cells were complex compared to the prebiotic molecules that preceded them, see Image 1. (NBSR) As of this writing, no known experiment has been shown to convert chemistry to biology.
Early Life on Earth
Earth was a very different place in the first 2 billion years of its existence. The air was toxic and lacked oxygen. Photosynthesis of cyanobacteria was the reason for the eventual build-up of oxygen in the atmosphere. (BBC) This means early life must have been ‘extreme’ compared to life as we commonly see it currently. Fossils of organisms called stromatolites are some of the oldest organisms we have significant evidence for. Stromatolites are prokaryotic cyanobacteria that grow in mounds in layers and have been studied widely. These organisms lived in the harsh carbon dioxide filled atmosphere of early Earth and are responsible for the oxygenation of our atmosphere. (Indiana) The Earth was awash with single celled organisms for billions of years. Eventually, multicellular organisms appeared 1.5 billion years ago. These organisms would be considered extreme compared to what we commonly see on Earth today, due to the differing percentages of atmospheric components, see Figure 1. Organisms on Mars would likely be microbes that are happy in extreme environments, called extremophiles.
Extremophiles
Extremophiles are organisms that survive under conditions that would be lethal to humans and to most of the organisms that a common person would recognize. Astrobiologists have discovered thousands of species of extremophiles which is essential for the search for life on Mars. These organisms push the boundaries significantly of what the definition of life once was. It is now known life must have a source of energy in order to metabolize and reproduce and a liquid solvent, that solvent on Earth is water. Nearly every niche astrobiologists study on Earth contains an extreme organism. Examples are; thermophiles which thrive in extreme heat, methanogens that consume methane, cryptoendoliths who live in rocks and live off of the minerals the rock is composed of, alkaliphiles thrive in high pH, halophiles love salty conditions which include perchlorates, radioresistant organisms resist high doses of radiation, lithoautotroph eat rocks, oligotrophs live in high sugar environments, and cryophiles can survive extreme cold. All of these organisms live in areas that are very far from the traditional areas where life was once believed to thrive, see figure 2. Previously we believed life needed sunlight, water, a food source, and to exist between 0oC and 100oC. Astrobiologists have now discovered this is not always the case. To explore the possibility of extant life on Mars, one must examine the ability for life to survive in a harsh environment.
Organisms have been found living in deep caves completely without sunlight and thriving. One example of this is called the Kentucky cave shrimp. It is a blind and almost transparent troglobite shrimp (Lisowski 1983). Also, several organisms, such as diatoms and algae, have been discovered living happily in the Arctic and Antarctic Sea ice (Colorado). In addition, the bottom of the ocean contains hydrothermal vents that are under extreme pressure and high temperature. At these vents are entire ecosystems of extremophiles. They include millions of bacteria, several species of tube worms, shrimp, crabs, fish and many other organisms. The pH at the vents throughout the world have been measured to be as low as 2.8 (acidophile) and as high as 10 (alkaliphile). (Seasky)
Deinococcus radiodurans is a bacterium that is known to Astrobiologists as an extremely radiation resistant organism. A lethal dose of radiation for a human is 5 gray units (Gy) A typical medical x-ray is about 1 mGy (milli grey unit= 0.001 Gy). This hardy organism can resist a dose of 5,000 Gy with no loss of viability and 15,000 Gy with a 37% viability rate. Deinococcus has also been known to be resistant to cold, dehydration, the vacuum of space, and acidic environments. It is known as a polyextrmophile. A polyextremophile is an organism that possesses many different characteristics of extreme organisms. (McKay 2010)
Another example of a polyextremophile that is a more complex, multi-cellular organism is the tardigrade, more commonly known as a water bear. They are not true extremophiles because these organisms are not adapted to live permanently under these conditions. They are amazingly resistant to almost anything nature sends their way. They are approximately 0.5 mm in length, with four stubby legs, and a slightly segmented chubby body. Water bears can be found just about anywhere one looks. They have been found from the Himalayas to 13,000 feet below the ocean and everywhere in between. The pressure differential is tremendous between these areas. Tardigrades can be heated to over 150oC and chilled to -200oC and survive. They have been taken to space, exposed to the vacuum and solar radiation for ten days, brought back to Earth, and survived. Water bears, see image 2, have the ability to resist exposure to 5,000 Gy of radiation. It has been reported that Tardigrades go into a state of chemobiosis in order to resist any environmental toxins that they are exposed to. Recently scientists have discovered that water bears have an unprecedented number of genes that are called “foreign DNA”. This means that over the millennia, tardigrades have taken advantage of the DNA of other organisms that evolved traits that are attractive to them and their survival. (NatGeo)
The Desulforudis audaxviator bacterium is an extremophile that lives underground sans oxygen or sunlight. Mars lacks a significant amount of O2 in its atmosphere and the underground water on Mars would be a suitable environment for the brave traveler. This bacterium lives alone in its ecosystem and survives by converting chemical energy into a source of fuel for metabolism, or chemosynthesis. (Chivian 2008)
On November 28, 2012 it was widely reported that scientists had finally reached the salty water of Lake Vida in Antarctica. This lake has been isolated from the rest of the world for at least 2,800 years. The water in this lake has a salt content five times that of the ocean and is below the freezing point. Even with these extreme conditions, scientists discovered 32 species of bacteria. This number was higher than expected and this study still continues. (Nature3) It is important to study extreme organisms to come to an understanding of the limits of life. It seems we are pushing those limits further and further every day. Mars is a plausible candidate for extant life due to the aforementioned incredible research and results that have examined extreme organisms in extreme environments.
Follow the Water
Scientists have carefully studied and tracked the history of water on the Red Planet. The presence of water on Mars would indicate a much higher probability for extant life as we know all life on Earth depends on liquid water. Using Earth as an analog is the foundation for the search for life on Mars. It is now widely accepted due to the geomorphological evidence that Mars had an ocean of liquid water billions of years ago. This ocean covered the northern hemisphere. This is indicated by the lower altitude of the surface, smoother and geologically newer surface of the northern hemisphere, as opposed to the higher altitude and the more jagged appearance of the highlands of the southern hemisphere. An ocean covering most of the northern hemisphere has consequences such as a thicker atmosphere and warmer temperatures. It is clear by photographic evidence that volcanic activity was very active in Martian history. In close proximity to ancient volcanoes are areas of catastrophic flooding, caused when volcanic heat rapidly melted the subsurface ice. This evidence can still be seen today. (Martin-Torress 2015) Mars has a significant CO2 atmosphere, which would have been important to sustaining a warmer and wetter planet in the past. This thicker atmosphere could have been in place for 10 million to a billion years. Volcanism and cycling of carbonate rocks would have helped to keep the atmosphere intact for this lengthy geologic time. (Pollack 1987) Current science indicates Mars was once a warm and wet planet and currently has liquid water on the surface for short periods of time. Data consistent with liquid water has been observed. It is proposed water appears seasonally as minerals are mixed with water that erupts through the surface and runs down the sides of craters, keeping it liquid at temperatures below freezing. Ample evidence has been detected, morphologically and spectroscopically, from the fleet of spacecraft that have been and are now presently working on and around Mars. Water is the key ingredient for all life forms present on Earth.
Viking
Mars is widely considered to be the second most habitable planet in the solar system. A fleet of spacecraft have flown by, orbited, roved and landed on Mars since the 1960’s, desperately looking for life or possibly a civilization. When Mariner flew by Mars in 1965, hopes for finding a thriving civilization on the Red Planet were dashed by the 22-postage stamp sized images that slowly trickled back to Earth. The images showed a barren, rocky terrain. The Viking I and II missions by NASA were composed of two landers and two orbiters. The orbiters imaged the entire planet while taking scientific data readings, including an infrared spectrometer, to seek and track water vapor in the atmosphere. The landers took images from the surface and sampled the soil and atmosphere on opposite sides of the planet. Viking I landed at 22.27°N 47.95°W and Viking II at 47°38′24″N, 225°42′36″W. (NASANatl) The Viking Orbiters’ instrument, called the Mars Atmospheric Water Detector, detected upwards of approximately 100 microns of atmospheric H2O. (Farmer 1977) Atmospheric water is an important discovery in order to establish a baseline for a planetary water cycle and potential for microbial life to eke out a living on Mars. Rampart craters were photographed by the Viking orbiters. The craters are surrounded by what appear to be muddy flows. This is called fluidized ejecta, a type of muddy mixture, and is the result of the friction from an impact of a meteorite and the subsurface ice which interacted. The melted ice and regolith mixed together during the event and created the fluidized ejecta that is seen surrounding the rampart craters. (dePater & Lissauer)
Viking and the Search for Life on Mars
In 1976 a life detecting experiment invented by Dr. Gil Levin was sent on the Viking I and II Landers to investigate whether microbial life existed in the soil on Mars. Levin’s experiment was called the Labeled Release (LR) experiment. Viking I and Viking II, which were 4,000 miles away from each other, both carried the LR. A brief summary of the LR is as follows, first a sample of Martian soil is scooped up and sent into a small tube, then a squirt of nutrient radioactive 14C is added to the soil sample, and if microorganisms are present they will consume the nutrient and then give off radioactive gas. When the LR was performed on the surface of Mars, the first scoop of nutrient was added to the soil and a spike was seen on the graph indicating a positive result for life. The gas that was released by this experiment persisted for the entire seven days it was run. In order to verify the results a control experiment had been designed by NASA. The control was designed to determine whether the result was chemical or biological. The control had a negative result. Chemistry cannot “die” from an experiment, but biology can. Since the control came back negative and the LR was positive, it has been ascertained by Levin and others that there is life on Mars. The LR detected life on Mars according to the criteria set by the Viking team at NASA, see figure 3. Viking I and II both had a positive result for life with the LR experiment. Two other life detecting experiments were in the payload of Viking. Each one had varying degrees of sensitivity. The LR was the only test that was positive for life, but it was much more sensitive than the others. 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 & Straat 2016)
The Gas Exchange (GEX) and the Pyrolytic Release Experiment (PR) failed to detect life in the soils of Mars. NASA made a consensus that there was no life on the Red Planet, due to the chance that these results may have been chemical organic reactions. (Levin) Subsequent rovers and the Phoenix lander detected perchlorate in the regolith on Mars. Perchlorates have been found to be a source of energy for certain extremophiles on Earth, for example Halomonas elongate, which survived in a 0.4 M perchlorate solution with NaCl. (Oren 2013) Regarding the LR, NASA has determined that heating a sample with perchlorate would destroy any chance of detecting organics. (Cosmology) The scientific method states that results should be reviewed and retested, therefore if one out of three tests is positive, then you must rerun the experiment to get an accurate result. NASA planetary scientist Chris McKay, PhD. stated that the LR “detected perchlorate and its oxidizing products,” and in order to find extant life on Mars we should send “an instrument to search for amino acids and their homochirality and to search for lipids and their distinctive biological patterns.” (McKay 2020)
NASA has not sent any other true life detection experiments to Mars since Viking. They have only sent experiments to detect biosignatures. “I have requested for years - a thorough objective review by qualified scientists of all evidence for and against extant life on Mars. We have learned so much since Viking, I think the verdict would come down for life. In my 2019 article in Scientific American, I point out that the Viking LR test is very simple and, in essence, is the method used Daily by public health authorities around the world to test drinking water for microbial contamination. We strengthened that test by adding strong controls, all of which supported life. Each test was duplicated in each of the two replicate Vikings which landed 4000 miles apart. Since Viking, we have learned it would take a miracle for Mars to be sterile. It's time for a new paradigm announcing that we are not alone in the universe,” states Gilbert Levin, PhD. in a 2020 email exchange regarding extant life on Mars.
Mars Global Surveyor
The Mars Global Surveyor (MGS) orbiter reached orbital insertion in September 1997, shortly after the Pathfinder mission arrived it was tasked with many things, some of which were determining the geological processes that occur; imaging the surface seeking evidence of past water erosion; examining the physical properties of ice; monitoring the polar ice caps; and tracking weather patterns and the seasons. MGS had a suite of scientific instruments which included cameras, a laser altimeter, and a spectrometer. The instruments worked together to give planetary scientists a clearer picture of the history of water on Mars. One such instance occurred when MGS imaged the same crater six years apart. To the surprise of the scientific community, there had been a change in the crater wall. The crater lies in the Centauri Montes region at 38.7o S 263.3o W. The image in 1999 showed a non-distinct crater. In 2005 when the crater was imaged again, a sediment trail was identified, see Image 3. Spectroscopy indicated that the sediment was made up of salts and minerals that could be the result of briny water that flowed down the slope of the crater. When the water evaporated, a dry sediment of minerals would have been left behind, as indicated by the bright material imaged by MGS. (NASA) Some scientists stated the sediment could have been caused by water erupting through a weak spot on the crater wall, staying liquid due to the salt and minerals, flowing down the side of the crater, the water evaporating, and leaving remnants of minerals behind. Over the duration of the MGS mission, many more gullies were discovered. (NASA) Scientists know life exists on Earth in below ground water reservoirs, if the source of the MGS sediment discovery is water, it indicates a source of water below the surface of Mars where life could utilize the water to survive.
Another interesting clue to the history of water on Mars was when the Thermal Emission Spectrometer (TES) on board the MGS discovered vast amounts of hematite consistent with forming in water. Hematite is found abundantly on Earth and has been widely researched and found to be formed when the interaction of iron and water occur over long periods of time. Hematite forms in spherule shapes, concreting over time. (Geo2)
Mars Reconnaissance Orbiter
The Mars Reconnaissance Orbiter (MRO) entered the orbit of Mars in March 2006, a few months before NASA lost contact with MGS. The MRO also carried cameras and spectrometers. The HiRISE camera has imaged many RSLs, see Image 4. In 2015 NASA announced MRO had discovered hydrated minerals in the area of the dark streaks on steep slopes. The RSLs grow and recede with the temperature and seasonal changes and appear more commonly at mid-latitudes where the temperature is warmer. (NASAjpl) The streaks appear more often as Mars’ axial tilt aims the areas toward the Sun and the temperature reaches -23oC. This is below the freezing point for fresh water on Mars. (McEwen 2013) However, water that contains perchlorates and other minerals, dubbed hydrated salts or briny water, can exist at the temperature and pressure on Mars. (NASAjpl, McEwen 2013) The aforementioned extremophiles are able to survive and utilize perchlorates and other minerals as a source of energy.
Other scientists have proposed water is not the cause at all but instead blocks of CO2 ice moving down the slopes are causing the linear gullies. The theory proposes that as the seasons change blocks of CO2 ice are loosened by sublimation. Blocks of carbon dioxide ice then fall down the steep slopes carving gullies that appear to be evidence of flowing water. (Diniega 2013)
Spirit and Opportunity
The Mars Exploration Rovers Spirit and Opportunity (MER) landed on Mars a few weeks apart in January 2004. Each rover contributed greatly in the search for evidence of water in order to lay a baseline for Martian habitability. Steve Squyres, Principle Investigator for MER, stated the mission was a “follow the water” mission. (NASA) Early in the history of Mars a large planetesimal hit the planet and melted the entire surface, this is known as the Borealis Impact. Any water or life that existed on the Red Planet would have been vaporized, unless it was living underground. The “follow the water” mission of the MER was tasked with finding out if water existed on the surface of Mars after the Borealis Impact. The Opportunity Rover landed at 1.94°S 354.47°E and explored Eagle Crater at Meridiani Planum shortly after landing on Mars. As images from the area were processed and viewed by the geologists on the team, it was discovered that a vast field of hematite had been discovered. The hematite was nicknamed “blueberries” due to the bluish hue in the images and the appearance of a spattering of blueberries on the ground. (Universe) The Opportunity Rover used the Rock Abrasion Tool (RAT) to grind and examine a blueberry. The team next used a spectrometer to determine the mineral content of the nodule. The spectroscopic analysis revealed the concretion to be hematite and jarosite, see Image 5. (Klingelhofer 2004, JPL)
The Utah desert is home to a vast region of fossilized sand dunes that is a perfect analog to Eagle Crater and the surrounding Meridiani Planum on Mars with its own vast area of fossilized sandstone and hematite. Hematite only forms in the presence of water. Water penetrates the sandstone and pours through the cracks. As the water contacts the rock it brings with it minerals, like iron, that forms concretions around the sand. The dense iron nodules fall out of the sandstone as wind erosion dissipates the rock around the nodules. Over millennia, more blueberries fall out of the sandstone and pile up on the surface of the planet. For the tens of thousands of hematite nodules found by the Opportunity Rover, vast amounts of water must have existed on the surface of Mars. The water could only be sustained in liquid form with a much thicker atmosphere. The atmosphere also must have been much denser in order to cause the amount of wind erosion seen that caused the hematite to fall out of the sandstone. (Universe)
Spirit landed in January 2004 at 14.56°S 175.47°E in a dry lake bed. By March the Spirit Rover found evidence of past water in a rock named Humphrey. The MER team instructed the rover to examine Humphrey with the RAT which ground 2mm into the surface of the rock. It was discovered that the crystalline structures inside Humphrey had been in contact with water in order for the crystal to form. (NASAPress)
Spirit roved Mars for over 1200 sols when she was nearly crippled by a wheel that was no longer operational but continued to rove and drag the wheel behind her. As the wheel drug through the regolith, a white powdery substance was revealed. The substance was examined by the X-ray spectrometer and determined to be 90% pure silica. Squyres stated, via teleconference, this was a “remarkable discovery”. Silica is often found on Earth in areas where hot springs exist. The silica discovered by Spirit may have formed in a hot spring and later have flowed to an area further from the source. Another option for the formation of silica in the region is possibly the interaction with acidic vapors from volcanic activity combined with the regolith and water. (NASAmer)
At Gusev Crater in the Columbia Hills, Spirit examined a grouping of rocks, including a rock named Clovis. The team investigated Clovis utilizing the Mossbauer spectrometer which revealed the presence of eight iron bearing minerals including goethite, which only forms in the presence of water, see figure 4. (Morris 2006) The preponderance of evidence from the Spirit and Opportunity Rovers for past liquid water on Mars, is an essential clue in the search for extant life on Mars.
Phoenix
The Phoenix Lander landed near the north polar region at 68.22oN 125.7oW on Mars in May 2008. The lander used a parachute and reverse thruster, retrorockets landing method. (Phoenix) Notable images from Phoenix included a vast panorama of polygon shaped regolith which were indicative of ices beneath the regolith that had frozen and thawed, thus leaving behind a polygon shape. The polygons are formed by the freezing and thawing process as the regolith is blown by the wind and into the cracks in the ices, see Image 6. The camera on the underneath of the lander 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. The most intriguing photos were taken over a period of approximately 30 days and 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. Any extreme organism in the area could utilize the perchlorates as a mechanism to draw water to them, as water follows salts. This serendipitous discovery is yet another indicator for the habitability of Mars, even in the most extreme areas of the planet. (Martinez & Renno 2013) This elemental composition was later proven to be the reason the water could stay liquid at sub-zero temperatures and pressures far below that of Earth. (Astrobio2, Hecht 2009)
The Phoenix lander also imaged, for the first time, water ice clouds and snow falling. The temperatures at the time were not cold enough to form CO2 clouds which requires -120o C. Instead the temperatures hovered between -97.7 o C and -19.6 o C and would be conducive to H2O clouds and snow, further demonstrating a water cycle on Mars, which is essential for organisms to survive. (Spiga 2017)
Mars Science Laboratory Curiosity
As technology 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 the sky crane landing method has allowed for the landing of unprecedented payloads on the surface of Mars. The Mars Science Laboratory Curiosity (MSL) is an 899 kg rover that landed in August 2012, via the sky crane landing method. The rover has an entire laboratory on its back, many cameras, and a versatile arm. When NASA was deciding on a landing spot for Curiosity it was important to find an area with evidence of previous water activity in order to assess habitability. Gale Crater is only 4.5o south of the equator and is the site of a significant alluvial fan from previous water activity. Within a few days after Curiosity landed at 4.58°S 137.44°E, it was announced by John Grotzinger, Project Scientist for MSL, on a NASA telecast, that Curisoity had landed in an ancient riverbed that had 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. This discovery was made initially by the photographs 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, see Image 7. Another clue to the ancient riverbed was the rounded pebbled seen 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 significance of this discovery cannot be overstated, this indicates a pure, fresh water environment where organisms could thrive, similar to the many habitats on Earth.
The Curiosity team also discovered perchlorates in Gale Crater. Perchlorates allow water to be liquid at temperatures below freezing as well as a source of energy for extremophiles on Earth. Liquid brines can form in the pre-dawn hours on Mars. It has been proposed that within 5 cm of the surface, liquid brines form in Gale Crater. This liquid evaporates after sunrise. Studies up to 15 cm beneath the surface indicate that an exchange of atmospheric vapor interacts with the surface regolith and through deliquescence liquid water forms. (Martin-Torres 2015)
Desiccated mud cracks have also been discovered in Gale Crater, see Image 8. This implies liquid water stood for a period of time, around 3 billion years ago, and mixed with the regolith making mud. The water evaporated from the mud and what was left were polygon shaped muddy cracks. The cracks were buried over time by sediment that was blown across the surface. In more recent geologic history, the sediment was eroded away and what we see now are the remnants of dried mud cracks that were filled with sand. In close proximity to the mud cracks were layers of mudstone and sandstone. This indicates periods of time when a body of water was sitting in the area. The water would have moved somewhat tidally over the boundary of the lake and what is left behind are areas that appear to be a lakeshore. Another point of view is that the mud cracks could have been formed during a dry period of blowing sediment. Either way, indicating a dry period is by default pointing to a period of water in the area. (JPLnews) The data collected will continue to be studied.
Mars Express
ESA’s Mars Express Orbiter entered orbital insertion on December 25, 2003. The orbiter has been mapping the planet for over 16 years. In 2016 it was reported that the orbiter’s instruments detected a large subsurface salt-water lake. The lake is 1.5 km below the surface of the south polar region of Mars and covered a 20km wide area, with an unknown depth. Scientists report the amount of briny water is at least approximately equivalent to one of the Great Lakes on the US/Canadian border. Briny water with salts as in the form of perchlorates can maintain the liquid form to a temperature of -75o C. This lake would be akin to the aforementioned Lake Vida in Antarctica and may be a place life can persist and thrive. (Orosei 2018) Mars Express also detected 2200 cubic km of water ice in Korolov Crater at 73o North latitude and 165o East longitude. (Brothers Holt 2016) Life on Earth likely started in briny ocean water. Briny water contains many essential nutrients that microbial and even multi-cellular organisms thrive in. The subsurface lake on Mars is an excellent place to search for extant life with future missions to the Red Planet.
Methane on Mars
Methane persists for only a few centuries in a planetary atmosphere. Any data consistent with methane on Mars is a major indicator for existing life on Mars. On December 16, 2014 at the American Geophysical Union conference in San Francisco, a panel of scientists working on the Mars Science Laboratory (MSL) Curiosity Rover data announced what we have all been waiting decades to hear. John Grotzinger stated unequivocally, “…there is methane occasionally present in the atmosphere of Mars and there are organics preserved in…rocks on Mars.” (Marlow 2014)
Methane (CH4) is made up of one carbon and four hydrogen atoms. Approximately ninety percent (90%) of methane on Earth is produced by bacteria and other life, whereas ten percent (10%) is produced geologically, see figure 5. We know from studying life forms on Earth that methane is a common organic molecule that is a waste product of bacteria and macro organisms. According to author Jeffrey Bennett from the University of Colorado, Boulder, “The amount of methane in the atmosphere appears to vary regionally across Mars, and also seems to vary with the Martian seasons. This has led some scientists to favor a biological origin…if the source is volcanic…the amount of…heat necessary for methane release [could] be sufficient to maintain pockets of liquid water underground.” (Bennett)
The Curiosity Rover’s SAM and CheMin instruments found CHNOPS in a sample of the rock called John Klein that was drilled on Mars, see figure 6. (NASA, JPL) These molecules were also found at the Rocknest site in an earlier soil sample taken by Curiosity. The discovery of organic molecules is the most important and remarkable evidence that scientists have been waiting for the confirmation of. (Archer 2013) Another significant find is the electrochemical gradient of the different molecules found inside of the John Klein rock. An electrochemical gradient is another important piece of the “life on Mars” puzzle because life forms use these gradients to move ions across membranes in order to perform many metabolic and other biological functions. Some of the molecules found in the rocks have different electric charges; some are more oxidized than others. This was cleverly illustrated at a NASA press conference, wherein Dr. Grotzinger held up a battery to demonstrate the way rock eating microbes utilize the energy gradients formed by molecules, such as sulfates and sulfides, to their advantage in their metabolic processes. (NASAtv)
The importance of this discovery is all life on Earth that we have discovered so far is carbon based. Carbon is found in the DNA of all life forms on Earth and can bind with many other elements to form thousands of organic molecules that are involved in biological processes. Finding organics and methane is an incredible discovery that supports the evidence of the probability of extant life on Mars. Organics in general refer to molecules that are often found as components of life. We know from studying life forms on Earth that methane is a common organic molecule that is a waste product of bacteria and macro organisms. According to author Jeffrey Bennett from the University of Colorado, Boulder, “The amount of methane in the atmosphere appears to vary regionally across Mars, and also seems to vary with the Martian seasons. This has led some scientists to favor a biological origin…if the source is volcanic…the amount of…heat necessary for methane release [could] be sufficient to maintain pockets of liquid water underground.” Pockets of liquid water would be conducive to life and it has been confirmed that liquid water is occasionally present on the surface Mars and is likely to exist in the subsurface. The aforementioned Viking I and II Labeled Release Experiment which made an inconclusive discovery of life on Mars also discovered methane at 10.5 parts per billion (ppb) in 1976. Decades later, while utilizing the NASA Infrared Telescope in Hawaii, Michael Mumma, of NASA Goddard, observed methane using ground-based instrumentation in 2003. Mumma and his team’s observations were made over a heavily fractured region on Mars called Nilli Fossae. “We observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane,” stated Dr. Geronimo Villanueva, part of Mumma’s team, from the Catholic University of America in Washington DC. When he followed up the observations in 2006, the methane had vanished. Some scientists have stated that is indicative of a seasonal plume. According to NASA’s astrobiology website Mumma and his team observed 20-60 ppb of methane near the poles and up to 250 ppb near the equator, see image 9. It is interesting to note that the levels of methane are significantly higher near the equator where the temperature is higher and possibly more conducive to life.
The European Space Agency (ESA) announced in 2004, they had discovered plumes of seasonal methane on Mars. ESA announced that the Planetary Fourier Spectrometer (PFS) on Mars Express detected about 10 ppb of methane in the Martian atmosphere. Although ESA and NASA themselves had previously detected methane on Mars, it was important to continue the search.
The Curiosity Rover continued the search for methane and water, among other things. It seemed that almost as soon as the Curiosity started exploring her new home on Mars, she made a plethora of discoveries including the above-mentioned dry riverbed where fresh water once flowed in Gale crater. When MSL’s instruments drilled into and examined the rock dubbed “John Klein” scientists realized that the rock contained what biologists call CHNOPS. Those are the six elements needed for all life on Earth to exist. Another discovery were “simple organics” in which the molecules included carbon. One of the most important discoveries included more complex organic molecules than previously discovered, such as methane and chlorobenzene. We know Mars is enriched with all of the same chemicals elements that are found on Earth for life to arise. This important discovery puts to rest the long debate about whether Mars has organics. As NASA continued utilizing MSL to search, in 2018, it was confirmed that the Curiosity Rover’s Sample Analysis at Mars (SAM) instrument’s tunable laser spectrometer again detected organics. A spectrometer is a device that “looks” at a sample of something, in this case atmospheric gases, and takes readings to determine what molecules make up the sample being observed. A computer-generated graph of some type is then read by scientists to analyze the spectral data.
The data returned results consistent with methane and other organics on Mars, including kerogens. Kerogens are long-lived larger organic molecules that make up most organic material on Earth. The methane that was discovered occurs in small localized plumes in Gale Crater. It has been determined that a seasonal cycle of methane exists on Mars, see Figure 7. The amount of difference between the least and most amount of methane detected is much larger than expected. With the more recent observations the amount of methane detected in Gale Crater changed by a factor of 3x. Scientists also discovered a phase lag exists which is a clue that something is happening in the subsurface of the planet. Following up with more detailed research, a paper published in 2019 by Marco Giuranna in Nature Geosciences, confirmed with the PFS on ESA’s Mars Express, confirmed that the 2 spacecraft observed the same magnitude of a methane plume in the same location. (Giuranna 2019) According to NASA’s astrobiology website, “The clear conclusion of these (and other) recent findings is that Mars is not a ‘dead’ planet where little ever changes. Rather, it’s one with cycles that appear to produce not only methane but also sporadic surface water and changing dune formations.” (Astrobio3)
The amount of methane reported over the past forty years on the Red Planet ranges from approximately 0.7-250 ppb from a variety of sources, NASA, ESA, orbiters, rovers, and ground based Earth telescopes. Methane dissociates and only has a lifespan of approximately 329 years in an atmosphere, which is a short time on a planetary scale. It then breaks down and recombines with other dissociated molecules into water and carbon dioxide. Therefore, since methane is present on Mars, it must be getting replenished biologically or geologically currently. Many peer reviewed scientific journal articles have been published regarding Martian methane and the possible explanations for its existence. Some of the potential sources of methane include the presence of life, volcanoes, hydrothermal vents, photochemistry and other geological processes. Cosmic dust includes organic rich material that may be coming into the atmosphere of Mars and hit by ultraviolet solar particles and converted to methane, then picked up by wind and destroyed by photochemistry. This seems unlikely with the recent amounts detected at the surface in Gale Crater. The water that is now known to exist on Mars may combine with the olivine present on the surface and serpentinize, causing a release of methane. A scenario that is looking more likely, due to the seasonal plumes and seepage, is biological life. Some microbes bloom during warming periods and lie dormant during times of cooler weather. “[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)
Meteorites from Mars
A Martian meteorite is a piece of rock that has been ejected from Mars via meteoritic impact or volcanic eruption and travels through space then lands on Earth. Many different classifications of meteorites exist, each with a distinct composition of elements. A meteorite tells the geologic history of the body it originates from. Several classifications of Martian meteorites exist, the basic categories are: shergottites, nakhlites, chassignites (collectively known as SNC meteorites), and OPX (orthopyroxene) Martian meteorites. Each category has sub-groups and crossovers and exceptions occur. The classification of shergottites contains rocks that are found to be basaltic to igneous. This classification gets its name from a meteorite that fell in 1865 in the town of Shergotty, India. Nakhlites are formed by an accumulation of crystals. Subgroups of nakhlites include clinopyroxenites and wehrlites. The classification chassignites were named after a group of cumulate meteorites that were discovered in Chassigny, France in 1815. OPX Martian meteorites are a smaller group rich in orthopyroxene, a common silicate material. (ISMP 2013)
The estimates vary greatly for the amount of material that falls to the Earth each year. Some scientists estimate that 37,000 to 87,000 tons of material falls to Earth annually, but of that only 4-5 tons are big enough to land and be collected. However, finding them takes time and patience. Meteorites could conceivably come from anywhere in the solar system. However, of particular interest to scientists are meteorites from Mars. Meteorites are studied extensively by astrobiologists for the purpose of finding organic compounds, amino acids, and possibly life forms. An estimated 250-300 pounds of known Martian meteorite material is in the possession of scientists on Earth. Meteorites can be found anywhere, but some places make them easier to find such as desert regions and Antarctica. The contrast of the light sand or white snow and the dark colored meteorites allows scientists to see the meteorites.
Meteorite ALH 84001 was discovered in 1984 in a region of Antarctica called Allen Hills. The classification for this rock is an OPX. This category is made up of achondrite meteorites which are a rocks that do not contain round chondrate spherules. An orthopyroxenite(OPX) is a rock made of orthopyroxene and pyroxenite. ALH 84001 has gotten more attention than any other in recent history. (ISMP ALH 84001 2013) The Allen Hills meteorite was studied by Dr. David McKay of NASA. He published an article in the Journal Science in 1996 that claimed meteorite ALH 84001 contained microfossils. This sent shockwaves through the scientific community and the world media. Dr. McKay used scanning electron microscope (SEM) technology to image very fine slices of the meteorite, see image 10. When he saw the images, he and his team determined that they were microfossils of bacteria that had been preserved in the meteorite from Mars, thus concluding there had been life on the Red Planet in the past and may still exist there now. Immediately other scientists started examining the evidence and some of them came to the conclusion that the results were an artifact of the SEM process and not life. (NASA 2009)
One group of scientists stated that the ‘fossil’ 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. (Precambrian) A group of scientists stand by McKay’s results and have helped to continue his research posthumously. Journal articles supporting and debunking the results are published on a regular basis. The objects inside the Allen Hills meteorite may never be proven to be microfossils. However, with the exponential increase of technological advancements we can use other meteorites to supplement the data we find to determine what the potential for life is on Mars and in our Solar System.
On 4 May 2020, scientists from the Tokyo Institute of Technology and the Institute of Space and Astronautical Science at Japan Aerospace Exploration Agency published a new and important discovery relating to the search for life on Mars through the Earth-Life Science Institute about ALH84001. (ELSI 2020) Atsuko Kobayashi and Mizuho Koike stated in a press release that the Martian meteorite contains biologically fixed nitrogen. Nitrogen fixation is necessary for organisms to utilize nitrogen in their metabolic processes. This type of nitrogen is found in wet environments, rich in organic materials. This indicates a habitat on early Mars that was favorable for life to take hold and possibly survive and evolve over the past few million years. Team member Kobayashi stated, “There are two main possibilities: either they came from outside Mars, or they formed on Mars. Early in the Solar System’s history, Mars was likely showered with significant amounts of organic matter, for example from carbon-rich meteorites, comets and dust particles. Some of them may have dissolved in the brine and been trapped inside the carbonates.” The team also discussed that Mars had been bombarded, similar to Earth, with organic matter from comets and meteorites. Regardless of the origin, scientists have proven organics, simple and complex, exist on Mars today and have in the past. Organic material can be geological and/or pre-biotic and is the basis of life on Earth. This discovery is an essential part of the search for past and the potential for present life on Mars.
The Sahara Desert in Africa is where a headline grabbing meteorite was found. This meteorite dubbed NWA 7034 has been found to be a 2.1-billion-year-old volcanic meteorite from Mars. This meteorite did not fit into any previous category of Martian meteorites and had to be given a new categorization called Martian basaltic breccia. (ISMP 2013) This was determined by examining the chemical signature of the object. It is nicknamed “Black Beauty” because it has a beautiful dark sheen on its surface. It is said to have been part of a Martian volcanic eruption that sent it off the planet’s surface or by a large meteorite that struck the surface of Mars with enough force to send the rock into the solar system, where it travelled for a couple of billion years until it landed in Africa. When the meteorite was examined it gave off a small amount of water vapor but compared to other Martian meteorites Black Beauty contained much more water. It also appears to have been altered by an interaction with surface or ground water on the surface of the Red Planet. The aforementioned fleet of spacecraft sent to Mars have confirmed several times over that Mars once had water on the surface and according to NASA may still have periodic outflows of surface water. (ISMP NWA 7034 2013) Scientists are excited because, while they vacillate the when and how to return the cache from Mars Perseverance, they now have another piece of Mars that they can hold in their hands and study here on Earth. NASA scientists have stated that this is the richest geochemical meteorite found to date. According to MIT planetary scientist, Dr. Ben Weiss, approximately one ton per year of Martian meteorites fall to Earth, which over time equals billions of tons of rocks from Mars have arrived on Earth. He states, as do others, “It is possible we are Martians.” (Weiss 2000)
Amino Acids
Scientists have examined comets and meteorites over the past few decades and discovered amino acids in several samples. An amino acid is a prebiotic organic compound, meaning it is a precursor to a self-replicating living organism containing DNA. Amino acids make up proteins and genes are sequences of nucleic acid bases which then make up a DNA strand. (Kvenvolden et al. 1970)
To better understand the significance of the amino acid discovery, imagine a nucleotide base as a letter in the alphabet, then group three together to code for an amino acid which is like a word in a sentence, next a protein is analogous to a sentence, a gene is like a chapter in a book, and the DNA strand is like an entire book telling the story of an organism. Amino acids are quite a complex molecule. To find them floating through our solar system on random objects we sample is indicative of amino acids being very common throughout our solar system, including Mars, and possibly the galaxy and universe as a whole. Discoveries such as these contribute to the search for life on Mars and other solar system bodies due to the extrapolation of data indicating how commonplace the complex prebiotic molecules are. Falling near Murchison Australia in 1969, the Murchison meteorite was witnessed falling to the ground. It is one of the most studied meteorites in the world. It is not thought to have originated from Mars, but the scientific findings of this space rock pose many questions for scientists, especially astrobiologists. This meteorite has been found to contain many amino acids, see figure 8. Some studies say 15 others say 20 or more. (ISMP 2013 Murchison) Although the Murchison meteorite is not from Mars, it begs the question, if there are amino acids in meteorites falling from the sky onto Earth, then why wouldn’t there be meteorites falling to Mars with the same organic material? NASA’s Dr. John Grotzinger explained that the organic compounds recently discovered by the Curiosity Rover may not have originated from Mars. It should not matter where the organic material came from. The organic compounds are there now. Of course, this excludes contamination from Earth. Everything on every planet came from somewhere else. We are a collection of material that came from the same swirling cloud of gas and dust. Therefore, if organic compounds are on one planet or satellite, then it is logical that all of the bodies in the solar system, and therefore galaxy, have the same ingredients for life. This has also been confirmed by spacecraft that have taken samples from cometary debris which also had amino acids in them. (Rietmeijer 2010)
The previously discussed meteorite ALH84001 had more surprises for scientists in the form of amino acids. Scientist used high performance liquid chromatography to examine samples of the meteorite and discovered trace amounts of several amino acids, including glycine, alanine and serine. It is proposed by the team that most of the amino acids are from terrestrial contamination but left open the possibility of the D-alanine amino acid being preserved in the Allen Hills meteorite from Mars. (Bada 1998)
The Nakhla meteorite was observed and retrieved shortly after its fall in Egypt in 1911. This meteorite has been determined to have originated from Mars. Nakhla has been studied for decades and was found to have the first aqueous alterations from a Martian meteorite in the form of carbonates and hydrous minerals. Nakhla was also found to have several amino acids that were likely of terrestrial origin, but much like ALH84001, the researchers stated, though, some amino acids may be endogenous to the meteorite. Glavin states that rapid contamination occurs with terrestrial material when meteorites fall to Earth. This causes issues when examining any material that has been collected from extraterrestrial environments. (Glavin 1999) Technology has improved greatly since the last millennium, allowing for scientists now to determine with much greater accuracy the origin of molecules such as amino acids and proteins in objects that fall to Earth, contributing further to the search for life on Mars and other worlds. During transcription of eukaryotes on Earth, DNA is the template used to produce an RNA molecule which then, through a process called translation, codes for a protein.
Proteins and Lipids
In February 2020, scientists reported the protein hemolithin was discovered in a carbonaceous chondrite meteorite called Acfer 086. Proteins are large molecules made up of amino acids, hence this is a very complex molecule to be found in an extraterrestrial body. Scientists at Harvard University studied the properties of the protein and discovered they differ from terrestrial proteins. This confirms the building blocks of life exist elsewhere and are not limited to an Earth environment. (McGeoch 2020) In order to determine whether extant life exists on Mars, scientists must search for patterns of complex organic compounds such as proteins, lipids and DNA. ESA’s Rosalind Franklin rover (previously the second ExoMars rover) is slated to launch in 2022. This rover carries a drill that can penetrate and retrieve samples from 2m below the surface, where organic materials may be present and possible extant life may thrive. At depth, any organism would be protected from harmful radiation, the cold temperatures, and would more likely have access to liquid water. An analytical lab called the Mars Organic Molecule Analyzer (MOMA) will be onboard to take drill samples and analyze them for detection of organic molecules. The instrument has the ability to search for the molecular fingerprints for life and determine the shapes and formulas of the molecules, such as lipid hydrocarbons. Identifying lipids would be a major step in identifying extant life on Mars. Lipids are important components of; the structure of cell membranes, cellular energy storage, and for cell signaling. (ESA2)
Conclusion
The Earth and Mars have many similarities including a 23 hour and 56 minute and 24 hour 37 minute solar day respectively, a similar axial tilt causing seasons to occur, a rocky surface with many of the same types of rocks and minerals (which may be used as a source of energy for extreme organisms), volcanic activity and hydrothermal vents past and/or present, water that is/was fresh, salty, acidic, and/or basic, magnetic fields (Mars has pockets of magnetism), and quakes. Now and perhaps most important of all, water, organic matter and methane. The fleet of rovers and orbiters that have arrived at Mars and sent back ample amounts of data, have proven an environment conducive to microorganisms existed and may currently exist on the Red Planet.
The reasons to search for life on Mars are often pondered by the public. Several reasons are of great import. Often an outcry from the public comes in the form of, “Why are we wasting money when there are so many other things we need to fix?” The answer to that is most of the budget for the missions to Mars goes to the salaries of those working on the projects, which goes into the economy and helps support many other businesses. The scientists that work on the missions and the missions themselves help to inspire young people, it helps them dream about a future in space, how to become and astronaut or scientist. The missions give hope to the youth for our future as it is part of being human to explore. Most importantly, the safety of Martian astronauts, or Marsonauts, is a priority. Humans have learned from our vast historical explorations of Earth; pathogens are dangerous and can be deadly. Scientists must identify any extant life in order to protect Martian explorers from organisms that are hazardous to their health.
Everything on every planet came from somewhere else. The solar system is a collection of material that came from the same swirling cloud of gas and dust that emerged from a nebula 5 billion years ago, Thereby, if organic compounds are on one planet or satellite, then it is logical that all of the bodies in the solar system, and probably the galaxy, have the same ingredients for life. The spacecraft that have been visiting Mars for 50 years have not detected any macro organisms, but scientists have discovered evidence of an environment conducive to microorganisms. Scientists now know the ingredients for life exist on Mars. Elements and mechanisms on Mars suggest an environment supportive of life is present. Some astronomers go so far as to speculate whether life could have been blasted off of Mars and seeded Earth with microbes. (Benner) Like a court case, the preponderance of evidence is overwhelming, concluding extant life exists on Mars. Physicist Brian Cox has stated, “The emergence of life on Earth might have been an inevitable consequence of the laws of physics, and if that is true, then a living cosmos might be the only way our cosmos can be.” The odds that life exists elsewhere in the solar system, including Mars, are increasing each day as we retrieve data from spacecraft on and around the Red Planet.
Yet, science does not operate like a court case, the scientific method requires duplicating the experiment many times with many scientific inquiries. More research needs to be carried out. The Mars 2020 Perseverance Rover is scheduled to launch in July and land on Mars a few months later in early 2021. The equipment on the rover will not directly detect extant life but will search for past life on Mars. She carries a cache for geological samples that will be stored and examined at a later date. Unfortunately, no funded plan has been put forward as to how, whether human or machine retrieval, and when the cache will be retrieved or examined. This is not going to make the case for life much more compelling any time soon. Microbial life does not leave abundant amounts of fossils that are easily detectable. One of the best ways to discover extant life on Mars is through a human mission on Mars. Humans have critical thinking skills and dexterity that machines do not. DNA sequencing would have to be done on sight. Contamination from Earth is a major issue due to humans having ten times more bacterial cells in and on their bodies than human cells. A second option would be to send a rover to Mars with a miniaturized sequencer, which has been discussed by J. Craig Venter of the Venter Institute. This would be more of a random sampling and could work if contamination issues were addressed. (MIT) The probability for extant life on Mars is high. Nevertheless, a probability is meaningless without a full and well examined data set. A belief in life on Mars does not take us any nearer to the scientific fact of extant life on Mars. This must be proven with facts through the scientific method.
References:
AGU2: American Geophysical Union. https://agu.confex.com/agu/fm14/webprogram/Paper14587.html. (Accessed 31 March 2020)
Archer Jr, Paul Douglas, PhD. et. al., 2013. Abundances and implications of volatile‐bearing species from evolved gas analysis of the Rocknest aeolian deposit, Gale Crater, Mars. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013JE004493 (Accessed 1 April 2020)
Astrobiology: Astrobiology Journal. https://www.liebertpub.com/doi/full/10.1089/ast.2015.1464
(Accessed 05 March 2020)
Astrobio2: Astrobio.net. https://astrobiology.nasa.gov/missions/phoenix/. (Accessed 3 April 2020)
Astrobio3: NASA Astrobiology. https://astrobiology.nasa.gov/news/breakthrough-findings-on-mars-organics-and-mars-methane/ (Accessed 12 March 2020)
Bada, et. al. 1998. A Search for Endogenous Amino Acids in Martian Meteorite ALH84001. https://science.sciencemag.org/content/279/5349/362 (Accessed 1 May 2020)
BBC: British Broadcasting Corporation. http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/earth_sea_atmosphere/earth_sea_atmosphererev3.shtml. (Accessed 10 March 2020)
Benner: Mars Society Education Forum. http://education2.marssociety.org/why-could-we-be-descendants-of-martians-issue-22/. (Accessed 12 March 2020)
Bennett: Jeffrey Bennett Speaking at the 17th Annual Mars Society Covention. https://www.youtube.com/watch?v=2KSnxCyoRHc&t=121s (Accessed 31 March 2020)
Brothers, Charles T. & Holt, John W. 2016. Three-dimensional structure and origin of a 1.8 km thick ice dome within Korolov Crater, Mars. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL066440 (Accessed 3 May 2020)
Chivian, Dylan, PhD. et. al. 2008. Environmental Genomics reveals a single species ecosystem deep within Earth. https://escholarship.org/uc/item/23x7d9r0 (Accessed 1 April 2020)
Chaisson & McMillan: Astronomy Today Text 7th edition. P.256.
Colorado: University of Colorado. http://huey.colorado.edu/diatoms/about/index.php. (Accessed 11 April 2020)
dePater & Lissauer: 2016. Planetary Sciences. P.208. Diniega, S. et. al. 2013. A new dry hypothesis for the formation of martian linear gullies. https://www.sciencedirect.com/science/article/pii/S0019103513001668. (Accessed 12 March 2020) ELSI: Earth-Life Science Institute. http://www.elsi.jp/en/news_events/highlights/2020/4_billion_year_nitrogen_molecules_martian_meteorites (Accessed 7 May 2020)
ESA: European Space Agency. http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_s_comet_contains_ingredients_for_life. (Accessed 21 April 2020)
ESA2: European Space Agency ExoMars page. http://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars (Accessed 3 May 2020)
Flinn: Flinn Scientific. https://www.flinnprep.com/Course/Environmental_Science/Planet_Earth/Planet_Earth (Accessed 2 April 2020)
Farmer, C.B. et. al. 1977. Mars: Water vapor observations from the Viking orbiters. https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/JS082i028p04225. (Accessed 12 March 2020) Geo2: Journal of Geophysical Research. http://www.utsa.edu/LRSG/Teaching/EES5053-06/Christensen_2000_Detection%20of%20crystalline%20hematite%20mineralization%20on%20Mars%20by%20the%20TES_JGR.pdf (Accessed 12 March 2020)
Giuranna, Marco, et. al. 2019. Independent confirmation of a methane spike on Mars and a source region east of Gale Crater. https://www.nature.com/articles/s41561-019-0331-9#auth-1 (Accessed 12 March 2020) Glavin, et. al. 1999. Amino acids in the Martian meteorite Nakhla. https://www.pnas.org/content/96/16/8835.full (Accessed 1 May 2020)
Hecht, M.H. et. al. 2009. Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site. http://science.sciencemag.org/content/325/5936/64.full?ijkey=BVZRNinUWg62c&keytype=ref&siteid=sci. (Accessed 3 April 2020)
History: History Channel. http://www.history.com/shows/ancient-aliens/season-2/episode-1. (Accessed 19 April 2020)
Indiana: Indiana University. http://www.indiana.edu/~geol105b/images/gaia_chapter_10/stromatolites.htm. (Accessed 7 April 2020)
InSight: NASA InSight Lander page. https://www.nasa.gov/mission_pages/insight/main/index.html (Accessed 1 May 2020)
ISMP 2013: International Society for Meteoritic and Planetary Science. 2013. http://www.lpi.usra.edu/meteor/metbullclass.php?sea=Martian+%28OPX%29 (Accessed 2 May 2020)
ISMP ALH 84001 2013: International Society for Meteoritic and Planetary Science. https://www.lpi.usra.edu/meteor/metbull.php?sea=alh+84001&sfor=names&ants=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name&categ=All&mblist=All&rect=&phot=&snew=0&pnt=Normal%20table&code=604. (Accessed 2 May 2020)
ISMP NWA 7034: International Society for Meteoritic and Planetary Science. https://www.lpi.usra.edu/meteor/metbull.php?sea=nwa+7034&sfor=names&ants=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name&categ=All&mblist=All&rect=&phot=&snew=0&pnt=Normal%20table&code=54831. (Accessed 2 May 2020)
ISMP Murchison 2013: International Society for Meteoritic and Planetary Science. https://www.lpi.usra.edu/meteor/metbull.php?sea=murchison&sfor=names&ants=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name&categ=All&mblist=All&rect=&phot=&snew=0&pnt=Normal%20table&code=16875 .
(Accessed 2 May 2020)
Kvenvolden et al. 1970: Kvenvolden, Keith and Lawless, James and Pering, Peterson, Etta and Flores, Jose and Ponnamperuma, Cyril and Kaplan I.R., Moore, Carleton. 1970. “Evidence for Extraterrestrial Amino-acids and Hydrocarbons in the Murchison Meteorite.” Nature. 228:923-26. (Accessed 2 May 2020)
JPL. JPL Arizona State University. http://phoenix.lpl.arizona.edu/mars153.php (Accessed 3 April 2020)
JPLnews: NASA JPL Cal Tech News Release. https://www.jpl.nasa.gov/news/news.php?feature=6721. (Accessed 2 April 2020) Klingelhofer, G. et. al. 2004. Jarosite and Hematite at Meridiani Planum from Opportunity's Mössbauer Spectrometer. http://science.sciencemag.org/content/sci/306/5702/1740.full.pdf. (Accessed 12 March 2020)
Levin, Gilbert V. & Straat, Patricia A. 2016. The Case for Extant Life on Mars and its Possible Detection by the Viking Labeled Release Experiment. http://www.gillevin.com/Mars/Astrobiol_Paper_10-16_Levin_and_Straat.pdf (Accessed 05 March 2020)
Levin, Gilbert V. 2010. Extant Life on Mars: Resolving the Issues. http://journalofcosmology.com/SearchForLife107.html (Accessed 3 April 2020)
Levin, Gilbert PhD., email exchange dated 3 March 2020.
Lisowski, Edward, A. 1983. Distribution, Habitat, and Behavior of the Kentucky Cave Shrimp Palaemonias Ganteri Hay. https://academic.oup.com/jcb/article-abstract/3/1/88/2327899 (Accessed 7 April 2020)
Marspedia: Marspedia.org. https://marspedia.org/The_Curious_Case_for_Methane_on_Mars:_Methane_and_Active_Organics_Discovered_on_Mars (Accessed 05 March 2020)
Martin-Torres, Javier F. et. al. 2015. Transient liquid water and water activity at Gale crater on Mars. https://www.nature.com/articles/ngeo2412. (Accessed 6 April 2020) Martinez, G. M. & Renno, N.O. 2013. Water and Brines on Mars: Current Evidence and Implications for MSL https://link.springer.com/article/10.1007%2Fs11214-012-9956-3. (Accessed 24 March 2020)
McEwen, Alfred S. et. al. 2013. Recurring slope lineae in equatorial regions of Mars. https://www.nature.com/articles/ngeo2014. (Accessed 12 March 2020) McGeoch, Malcolm. W., et. al. 2020. Hemolithin: a Meteoritic Protein containing Iron and Lithium. https://arxiv.org/abs/2002.11688 (Accessed 1 April 2020)
McKay, Christopher P. PhD. email exchange dated 3 March 2020.
McKay, Christopher P. 2010. An origin of Life on Mars. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845199/ (Accessed 7 April 2020)
Meierhenrich, Uwe J. et. al.2004. Identification of diamino acids in the Murchison meteorite. https://www.pnas.org/content/101/25/9182 (Accessed March 31 2020)
MIT: MIT Technology Review. https://www.technologyreview.com/2012/10/18/183216/genome-hunters-go-after-martian-dna/ (Accessed 1 May 2020) Morris, R. V. et. al. 2006. Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2005JE002584. (Accessed 12 March 2020)
Nap: Nap.edu. https://www.nap.edu/read/11919/chapter/8#74. (Accessed 7 April 2020)
NASA: NASA Mission Pages. https://www.nasa.gov/mission_pages/mars/images/pia09028.html#.WsP_M4jwZPZ. Accessed 12 April 2020) NASA. 2009. “New Study Adds to Finding of Ancient Life Signs in Mars Meteorite.” http://www.nasa.gov/centers/johnson/news/releases/2009/J09-030.html. (Accessed 3 May 2020)
NASAmer: NASA Mission Section, Mars Rovers. https://www.nasa.gov/mission_pages/mer/mer-20070521.html. (Accessed 12 March 2020) NASAjpl. NASA Jet Propulsion Laboratory News. https://www.jpl.nasa.gov/news/news.php?feature=4722. (Accessed 12 March 2020) NASANatl. NASA’s National Space Science Data Center. https://nssdc.gsfc.nasa.gov/planetary/viking.html. (Accessed 12 March 2020) NASANews. NASA News. https://www.jpl.nasa.gov/news/news.php?feature=4722. (Accessed 21 April 2020) NASApress: NASA Press Release. https://mars.jpl.nasa.gov/mer/newsroom/pressreleases/20040305a.html. (Accessed 12 March 2020) NASAtv: Live broadcast NASA television. https://www.jpl.nasa.gov/news/news.php?feature=6809. (Accessed 12 April 2020)
NatGeo: National Geographic. http://tvblogs.nationalgeographic.com/2014/03/19/5-reasons-why-the-tardigrade-is-natures-toughest-animal/. (Accessed 18 April 2020)
Nature3: Journal Nature. http://www.nature.com/news/life-abounds-in-antarctic-lake-sealed-under-ice-1.11884. (Accessed 12 April 2020)
NBSR: National Bureau of Standards Report, 1965, NASA Archive. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650022476.pdf (Accessed 31 March 2020)
NCBI: NCBI US National Library of Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845199/ (Accessed 05 March 2020)
Noticias: http://noticiasseleccionvaldeandemagico.blogspot.com/2014/07/mgatp.html. (Accessed 19 April 2020)
Olympus: Olympus. https://www.olympus-lifescience.com.cn/en/microscope-resource/primer/techniques/phasegallery/paramecium/ (Accessed 31 March 2020)
Oren, Aharon. et.al. 2013. Perchlorate and halophilic prokaryotes: implications for possible halophilic life on Mars. https://link.springer.com/article/10.1007/s00792-013-0594-9 (Accessed 3 May 2020) Orosei, R. et. al. 2018. Radar evidence of subglacial liquid water on Mars. https://science.sciencemag.org/content/361/6401/490 (Accessed 3 May 2020)
Phoenix: NASA Phoenix Lander Page. https://www.nasa.gov/mission_pages/phoenix/overview. (Accessed 24 March 2020)
Phys: Phys.org News. https://phys.org/news/2015-11-huge-chunk-tardigrade-genome-foreign.html
(Accessed 2 April 2020)
Pollack, J.B. et. al. 1987. The case for a wet, warm climate on early Mars. https://www.sciencedirect.com/science/article/pii/0019103587901473?via%3Dihub. (Accessed 12 March 2020)
Precambrian: Life on Mars: evaluation of the evidence within Martian meteorites ALH84001, Nakhla, and Shergotty. Gibson, et al. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.539.6004&rep=rep1&type=pdf (Accessed 3 April 2020)
Research: Research Gate. https://www.researchgate.net/publication/225019299_Subsurface_Oceans_and_Deep_Interiors_of_Medium-Sized_Outer_Planet_Satellites_and_Large_Trans-Neptunian_Objects. (Accessed 19 April 2020)
Rietmeijer 2010: Rietmeijer, Frans J.M. 2010. “Stardust glass: Indigenous and modified comet Wild 2 particles.” Meteoritics and Planetary Science. 44: 1707-15. (Accessed 3 May 2020)
Rothschild, Lynn J & Mancinelli, Rocco L. 2001. Life in extreme environments. https://www.nature.com/articles/35059215 (Accessed 05 March 2020)
SciAm: Scientific American. https://www.scientificamerican.com/article/murchison-meteorite/. (Accessed 15 April 2020)
Seasky: Sea Sky Org. http://www.seasky.org/deep-sea/giant-tube-worm.html. (Accessed 19 April 2020)
Spiga, Aymeric. Et. al. 2017 Snow precipitation on Mars driven by cloud-induced night-time convection. https://www.nature.com/articles/ngeo3008. (Accessed 2 April 2020)
Universe: How the Universe Works, Life and Death on the Red Planet. Jani Radebaugh, BYU, (12 March 2020)
Weiss, Benjamin, P. et. al., 2000. A Low Temperature Transfer of ALH84001 from Mars to Earth. https://science.sciencemag.org/content/290/5492/791 (Accessed 1 April 2020)
Wikishrimp: Wikipedia Kentucky Cave Shrimp. https://en.wikipedia.org/wiki/Kentucky_cave_shrimp. (Accessed 18 April 2020) Zubrin, Robert: Conversation with Dr. Robert Zubrin March 2020.
