Searches for life on Mars have been hindered by one simple fact: no such creatures have ever been discovered despite our best efforts. This does not indicate lack of effort on our part.
One approach involves studying Deinococcus radiodurans bacteria, which have proven resilient against large doses of radiation exposure. Scientists think some microbes on Mars could have survived deep underground away from cosmic rays.
Temperature
Mars lacks an atmosphere similar to Earth, consisting of carbon dioxide, nitrogen and argon gases which give the sky its distinctive reddish-tan hue, along with an additional layer of oxidized dust. Daytime surface temperatures may reach as high as 70 degrees Fahrenheit while overnight lows drop below freezing, which poses dangers to human spacecraft landing operations.
Mars may once have had liquid water on its surface if its atmosphere were thicker; channels, valleys and gullies are found throughout its surface that suggest that once upon a time water flowed over it. Furthermore, Mars boasts one of the longest canyons in our solar system: Valles Marineris which spans an astounding 3,000 mile span across its surface.
Even with thicker atmospheres, however, water would still find it hard to stay liquid on Mars’ surface due to low atmospheric pressure which prevents solar energy absorption by water molecules – even during strong solar flares, which provide not enough heat to raise surface temperatures above 50 degrees Fahrenheit.
Scientists speculate that Mars’ water accumulation occurred mostly in its polar regions. Ice likely formed layers over time, much like tree rings provide clues as to their age. Layered areas contain minerals which could help scientists discern what happened in its original environment before it became the dry, barren desert of today.
Carbonates may provide oxygen on Mars by storing carbon dioxide within their molecules. When heated, carbonate minerals release CO2 gas that reaches the atmosphere where ultraviolet radiation from the Sun causes it to break apart and produce water vapor and carbon dioxide gas simultaneously.
Water vapor in the air can pick up heat from the ground, raising surface temperatures. This makes it hard for plants to thrive on Mars; tomato plants and other vegetables typically only thrive at temperatures over 70 degrees Fahrenheit; even then they typically only survive for several weeks on Earth and approximately one month on Mars.
Atmosphere
Mars is covered by an atmosphere that comprises only about one percent of its mass, consisting of carbon dioxide, argon, nitrogen, and hydrogen gases that trap heat from the Sun and cause its surface to be cold. Due to its eccentric orbit and low atmospheric pressure conditions, however, Mars often comes closer to solar radiation than Earth does at certain points; combined with low atmospheric pressure this causes temperatures to dip considerably on its surface.
There are areas on Mars where temperatures are warm enough for liquid water to exist in its liquid state, suggesting ancient rivers or flows had passed across its terrain and remain trapped underground within cracks or pores. There are streams, canyons and valleys scattered across this Red Planet where this could happen, suggesting ancient flows had traveled across its terrain – perhaps some may still remain trapped underground!
Although there is no sign of life on Mars today, scientists still hope to gain clues into whether life existed there at one point or another through studying rocks and soil samples from various NASA missions that have visited Mars – including Mars Reconnaissance Orbiter, MAVEN probes and Viking landers who conducted tests from samples collected on its surface – for signs. Unfortunately, no such signs have yet been discovered.
Scientists have utilized computer models to simulate conditions on Mars. They discovered that microbes could have once thrived near its surface, sucking up hydrogen and carbon dioxide from atmospheric conditions before chemical feedback caused global cooling that drove them deeper underground, possibly to their deaths.
Mars’ atmospheric pressure varies seasonally due to variations in its polar caps’ size and location, reaching its highest point during northern polar winter and decreasing around summer solstice in its southern half.
Sauterey of UArizona believes that, historically, Mars had a much denser atmosphere of carbon dioxide and hydrogen that provided a more temperate environment, permitting water to move freely across its surface and possibly supporting life. Under such conditions, methane might have been produced on its surface; this theory could account for methane plumes detected on its atmosphere; but this does not explain why such microbes flourish elsewhere on Earth, like hydrothermal vents along fissures in ocean floors for instance.
Water
All life on Earth requires water, and that’s why scientists are searching Mars for signs of liquid water both above and below its surface. Robot landers have studied river- or lake-deposited sedimentary rocks that show evidence that Mars was once wet, yet today its cryosphere (a layer of ice covering the planet) prevents any groundwater from reaching the surface and spilling out; scientists think anything that breaks through that barrier – meteorite impacts, volcanic activity or geological faulting could break it open and allow groundwater to escape and flow freely across its surface; valley networks and outflow channels have been detected by robotic landers supporting this theory. Valley networks have also been detected by robotic landers supporting this theory – robot landers have identified valley networks and outflow channels, providing further support.
Mars’ polar caps consist of both water and frozen carbon dioxide (or “dry ice”), with sublimating dry ice sublimating during winter months and disappearing completely in summer months. By contrast, warmer equatorial regions such as Valles Marineris feature pure water ice caps.
Mars derives its limited oxygen from water and carbon dioxide in its surface soils, with ultraviolet radiation breaking oxygen bonds very quickly; replenishment occurs only in very sheltered locations like its polar caps.
Evidence indicates that water may have flowed on Mars only recently; imagery from both Mars Reconnaissance Orbiter and Curiosity have revealed flood-like gullies within crater walls and sediment deposits indicating recent rainfall events, suggesting water could have made its way across these features as recently as several hundred thousand years ago.
Additionally, the APXS instruments onboard the rovers have measured several elements present in Martian rock and soil samples they’ve collected, such as argon. Argon content increases with rising temperature while fluctuating according to seasonal changes in air pressure in the polar caps; such fluctuations suggest methane may be produced through non-biological means like water-rock reactions or radiolysis of ice and CO2.
Mars may not support life for various reasons: its atmosphere is virtually devoid of oxygen and temperatures fluctuate widely; radiation exposure levels are also high while fluctuating ozone can damage cells. Yet Buzz Aldrin, one of two men to walk on the moon, has called for future manned missions to Mars.
Soil
Soil is home to millions of microorganisms, fungi and plants which provide food, shelter and energy sources for all living things on Earth. Furthermore, its minerals serve as commodities used to manufacture building materials, clothing and fuel products.
Although it may seem unbelievable that Mars ever supported life before now, planetary scientists have recently discovered evidence that its soil once hosted microbiological communities. Curiosity rover recently found evidence of boron in Martian soil which is essential in creating sugars required to make RNA, one of the key building blocks essential for life.
Mars regolith, or surface material, contains various rocks and minerals; most commonly basalts with components of pyroxene, plagioclase feldspar, and olivine. Over time these rocks break down through mechanical weathering processes until mechanical weathering leaves behind rich deposits of iron as well as essential elements that support plant life – these elements being essential to growth on Mars.
Scientific instruments aboard spacecraft and landers/rovers have analyzed the composition of regolith. This has broadened our understanding of its chemistry, leading to a new classification system for soils based on how minerals reflect light at visible and near-infrared wavelengths; quickly weathered minerals like pyroxene and olivine have low reflectance while those resistant to weathering, such as those found in some igneous rocks, have higher reflectance.
Scientists have developed soil simulants similar to what might be found on Mars and used these simulants to grow plants similar to what would exist there, however the nutrients that plants need cannot support growth under these harsh conditions. Researchers, including UGA faculty members Paul Schroeder, Mussie Habteselassie and Aaron Thompson are working on ways to enrich their soil in order to provide plants with nourishment they require for survival.
Research in support of Mars exploration is being funded by a technology company which is interested in designing tools to remove toxic compounds from soil, as well as systems to break up and aerate hard-to-irrigate soil layers. These tools would include ways of extracting those toxic substances while simultaneously breaking them up for easier irrigation.