Exploring the Salty Conditions of Life on Mars
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Chapter 1: Martian Climate and Its Implications
Recent evaluations of Mars' climate indicate that conditions may be even more severe than previously assumed. Surprisingly, this might actually benefit Mars exploration efforts.
Microorganisms from Earth that travel to Mars on spacecraft could find it difficult to survive in the planet's salty brine, according to a new study. This finding is promising for Mars exploration, as it reduces the chances of Earth microbes contaminating the Martian surface during landings. Protecting Mars from forward contamination by terrestrial life has been a goal for NASA and other space agencies since the dawn of space exploration.
Mars was once a planet abundant with water, and while pockets may still exist, they are likely to be too salty for Earth microbes to thrive. This discovery could safeguard Mars from contamination by life that may accompany spacecraft.
"This raises concerns for planetary protection policies due to the risk of biological contamination from Earth," researchers noted in a study published in Nature Astronomy.
Coming May 26: An interview with Dr. Alejandro Soto of the Southwest Research Institute, discussing the role of water on Mars and the implications of its salty conditions for exploration. video | podcast
Section 1.1: The Science of Brine
Investigators at the Southwest Research Institute (SwRI) found that Mars’ low temperatures and arid conditions would likely cause water to freeze, boil, or evaporate instantly. However, liquid water could potentially exist in highly-salty pockets scattered across the planet.
"Our team focused on specific regions of Mars where the temperature and availability of liquid water might allow known terrestrial organisms to thrive," explained Dr. Alejandro Soto, a senior research scientist at SwRI.
Although liquid water is not currently observed on Mars' surface, computer simulations indicate these saline pockets could exist from the equator to higher latitudes for limited timeframes, potentially up to six hours a day.
"These briny areas are quite small—smaller than a shot glass. We have captured images of possible droplets on the Phoenix lander that align with our laboratory research and modeling," Dr. Soto shared with The Cosmic Companion.
The persistence of these briny pockets is longer than previously believed, suggesting they may be more widespread on Mars than astrobiologists had thought. Nonetheless, the temperatures in these pockets remain too frigid for terrestrial life to endure.
The extreme dryness of Mars lowers the temperatures necessary for water to achieve humidity levels and water activity that can support life. Landers arriving on Mars risk contamination from Earth-based life; however, recent research indicates such life may not endure long.
"We utilized Martian climate data from atmospheric models and spacecraft observations to develop a model predicting where and for how long brines can remain stable on Mars," Soto elaborated.
Temperatures in these brine pockets are expected to reach a maximum of -48 Celsius (-55 Fahrenheit), which is around the threshold often considered the lower limit for sustaining life.
"Everyone interested in Mars is curious if any conditions exist that could allow life to persist on the planet today. Therefore, we examined whether the transient, unstable droplets of water and brine previously detected on Mars could support life as we understand it. However, the high salinity combined with low temperatures would likely inhibit the survival of known life forms," Soto explained.
Subsection 1.1.1: Resilience of Life
Life on Earth has proven capable of surviving in a variety of extreme conditions. Whether in extremely hot or cold environments, or in high-acidity or alkaline settings, some form of life manages to adapt and thrive. Even in total darkness or extreme dryness, life has evolved to utilize available resources.
"Life on Earth has expanded into nearly every conceivable, and at times inconceivable, ecological niche," stated Chris Impey from the University of Arizona in Tucson.
"Life breaks free. Life expands to new territories—painfully and perilously—but life finds a way."
― Dr. Ian Malcolm, Jurassic Park
Thermophiles, for example, can produce enzymes even in extreme heat. Discovered in an underwater vent in 1997, the organism Pyrolobus fumari can endure temperatures up to 113 degrees Celsius (235 degrees Fahrenheit). A related microorganism found beneath the Pacific Ocean, strain 121, can survive and possibly reproduce at temperatures reaching 121 Celsius (almost 250 Fahrenheit).
Conversely, studies indicate that the bacterium Colwellia psychrerythraea can endure temperatures as low as -196 Celsius (-320 Fahrenheit), which is the temperature of liquid nitrogen.
Notably, recent research identified Henneguya salminicola, a multi-cellular organism that can live without oxygen, showcasing the adaptability of life.
Tardigrades, known as "water bears," exemplify resilience as they can survive decades without food and endure extreme conditions, including the vacuum of space. Some speculate that a colony of these creatures might already inhabit the Moon, following the crash of the Beresheet spacecraft in April 2019.
Even in the hyper-saline environment of the Dead Sea, life persists. Despite its water being eight times saltier than the ocean, Haloarcula marismortui has evolved proteins enabling survival in such high salinity.
Research conducted by the Opportunity rover has revealed deposits of magnesium sulfate salts on Mars, possibly remnants of ancient oceans. Some scientists suggest this evidence indicates that Martian water may be too salty for life to thrive.
"Even the most resilient life forms on Earth have limits, and our findings suggest that brine formations from certain salts could yield liquid water across 40% of Mars' surface, albeit only seasonally for about 2% of the Martian year. This would likely render conditions unsuitable for life as we know it," Soto concluded.
If these findings hold true, it could indicate that life on Mars is either exceedingly rare or fundamentally different from life on Earth. However, it also suggests that the risk of contaminating Mars with Earth life may be lower than previously thought.
James Maynard is the founder and publisher of The Cosmic Companion. Originally from New England, he now resides in Tucson with his wife, Nicole, and their cat, Max.
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Chapter 2: The Search for Life on Mars
The first video, "How Salt Might Be The Key To Finding Life on Mars," delves into the role of salt in potential Martian life, discussing how briny conditions might influence the search for extraterrestrial organisms.
The second video, "Eighth Annual John Carlson Lecture -- Searching for Ancient Life on Mars," features insights into ongoing efforts to uncover evidence of past life on the Red Planet.