Studies on human settlement on Mars have been ongoing since at least 1960; however, only recently has there been any realistic chance for such an endeavor to become reality.
Travel to Mars poses numerous risks. Astronauts could experience bone loss as they remain immobile for long stretches.
Life on Mars
Mars’ surface is inhospitable to life. The terrain resembles Earth’s deserts in many respects, while its air is too thin for plants and too toxic for human breathing. Even if there was once liquid water present on its surface, atmospheric changes would quickly deplete it away; yet geological and chemical evidence points toward past habitability of Mars.
Mars once had a thicker, warmer atmosphere which may have allowed microbes to flourish; but after it lost its magnetic field billions of years ago, ionizing radiation slowly diminished life on Mars, breaking up carbon molecules which form organic life and breaking them down further into simpler molecules that form organic life forms. If microbes did establish themselves on Mars at one point, they might have eventually adjusted to this higher-radiation environment by moving deeper underground to avoid direct exposure to it.
Mars may have eventually hosted enough microorganisms to permit reproduction; however, as its environment changed again and necessitated relocation efforts of life forms; this cycle may have repeated itself many times throughout history preventing any one location from becoming permanent habitat.
At present, scientists are searching for signs of life on Mars by analyzing rock samples and chemical compounds found there, as well as mapping areas on Mars which might provide suitable habitats. Hellas Planitia in southern Mars as well as Jezero Crater where NASA’s Perseverance rover currently stores samples could potentially have hosted life at some point in history.
Some skeptics point to photos from NASA’s Curiosity rover which appear to depict life at various stages of evolution on Mars, but these could just be cases of pareidolia – where we perceive familiar shapes among random data sets – or because most Nasa photographs are black-and-white and hard to pick out any living organisms.
Atmosphere
Mars’ atmosphere is toxic for human life and predominantly composed of carbon dioxide, with long and dark winters freezing the CO2 directly into ice caps at both poles, leading to lower atmospheric pressure across most of its surface and producing much smaller greenhouse effects than on Earth resulting in very cold temperatures overall.
Mars’ unique climate pattern is also responsible for its legendary dust storms, which often last months or even years and reach tornado-size. Winds typically circulate cyclonically; however, due to planet rotation they can sometimes become blocked by nearby landforms and create localised weather systems, which gives rise to its unique weather system.
Mars shows evidence of running water through streaks of salts on steep slopes that change with seasons, as well as deposits of hydrated minerals near these streaks which suggest their deposition by water flowing across its surface.
Scientists have also made strides toward understanding the chemical makeup of Martian air, which largely comprises carbon dioxide with small amounts of nitrogen, oxygen and water vapor due to ground-based spectroscopy observations and spacecraft observations. MAVEN will allow scientists to further identify this atmosphere including abundance levels as well as isotopic ratios like 15N/14N or 40Ar/36Ar or 129Xe/132Xe).
Due to Mars being free from oceans, its atmospheric circulation is considerably simpler than on Earth. At low latitudes, Hadley cells (named after English scientist George Hadley 1685-1768) dominate, with rising, heated air sweeping from north to south in waves similar to what occurs here on Earth when trade winds form. When approaching polar caps however, air cools rapidly, sinks back and returns towards the equator over its surface before eventually returning back again over its surface back towards equator again.
Its atmosphere is extremely thin and dry, with seasonal pressure fluctuations reaching its minimum over the southern polar cap in winter and peaking over its northern counterpart in summer – this phenomenon being due to carbon dioxide moving annually between polar caps and Earth’s atmosphere; which is approximately 26 percent thinner.
Water on Mars
Water is one of the main obstacles to successful Mars missions, given that its gravity and atmosphere are much lighter. That means more liquid water escapes into space; as a result, for any human expedition to survive on Mars they would need enough food and water, as well as enough oxidants or air from greenhouses where they’d live to produce oxygen for breathing purposes.
Scientists have already been uncovering geologic evidence of liquid water on Mars, such as river beds and gullies. Furthermore, scientists have unearthed elements essential for life on the planet, suggesting it once offered more favorable conditions for microbes to survive on its surface. Curiosity landed on Mars in 2012 to continue this work; its chemistry set can detect whether Mars has ever provided sufficient conditions to support life both past or present.
The Mars Rover’s Gamma Ray Spectrometer recently detected signs of hydrogen in its soil, suggesting it once contained water. When high-energy cosmic rays reach Mars’s surface, high-energy cosmic rays send neutrons ricocheting from nuclei of planet’s atoms outward, only to quickly slow down and be recaptured by soil particles which emit characteristic energies of Gamma rays emitted by these soil particles and recaptured by their nuclei to emit characteristic energies of Gamma rays with characteristic energies emitted back outward – suggesting liquid water once existed there! The amount of hydrogen combined with temperature and pressure data indicates liquid water once existed here
Future discoveries could include more signs of water. But scientists first need to understand how these features form, making further study imperative. Images taken near Centauri Montes demonstrate this point; for instance, images show evidence that water was flowing along steep slopes only a few years ago!
If humans are to travel to Mars, their spacecraft must be robust and reliable, with enough room for food, equipment and extra fuel for return journey. Technologies must also be developed that enable efficient use of all resources – energy, water and oxygen among them – including those provided by Mars itself such as its ice caps; one possibility might be sending an advance spacecraft with provisions before people who will follow arrive; or setting up base nearby where meltwater can be converted into oxidants and propellant.
Bio signatures
Since 1960, scientists have been on an extensive mission to Mars searching for signs of life. Their goal is to find biosignatures – signs that microorganisms once existed there. Although difficult, this search for signs is one of the primary goals of space exploration; its success will help advance scientific mission objectives on the red planet.
Biosignature molecules must contain carbon, hydrogen, oxygen, nitrogen and possibly other ligands such as sugars or amino acids to be considered biosignatures. Furthermore, they must undergo biological processing as this allows living organisms to build complex structures and perform vital functions such as respiration. A variety of methods have been attempted at detecting biosignatures; none has proven conclusive; although two Viking landers landing on Mars in 1976 conducted some promising experiments that resulted in positive metabolic results from only one out of the four experiments conducted per Viking Lander; only one out of the four experiments produced positive metabolic results for metabolism results on each Viking Lander!
Problematically, however, the LR experiment was designed only to test one aspect of life on Mars and wasn’t as sensitive as modern instruments – meaning that Vikings failed to find evidence of it there.
Scientists are developing better biosignature detection methods by employing techniques that don’t rely on living organisms’ chemical makeup, like searching for metabolites released during organic degradation. Andrew Steele at the Laboratory for Agnostic Biosignatures is designing tools to be sent to Mars that can detect metabolites without being affected by Earth’s biochemistry; one such device uses microarray slides with antibodies attached that recognize certain molecules as targets for detection.
Gas chromatography and mass spectrometry techniques are then used to analyze the resultant molecule for its structure and isotope composition – potentially an invaluable addition to the tools required to discover life on Mars.