To understand the life that might survive deep below Mars’ surface, we can look to some of the deepest, and oldest, forms of living organism on our own planet.
On 12 August, US researchers reported evidence of a vast reservoir of liquid water, deep in the rocky crust of the planet.
Underground water on Mars opens up the possibility of underground life on Mars.
Martian life, if it exists, could well be subterranean.
The deep biosphere For over 30 years, biologists have accumulated evidence that life persists deep underground on Earth.
“There’s actually quite a lot of different types of organisms living deep underground,” says Cara Magnabosco, a geobiologist at ETH Zurich in Switzerland.
Like the slow microbes living deep under Earth’s oceans, Martian microbes may be clinging to life despite scant nutrients.
On Earth, methane is often made by microorganisms – so the gas could be a waste product from underground life.
Some of the oldest and deepest living forms on Earth can provide insight into the life that may exist beneath the surface of Mars.
Apart from its red color, Mars has a wet surface as well. US scientists revealed evidence of a sizable liquid water reserve located deep within the planet’s rocky crust on August 12.
The information was gathered over a four-year period from NASA’s Mars Insight Lander, which recorded over 1,300 Marsquakes. When scientists examined the seismic waves that reached the lander, they discovered that they had traveled through layers of wet rock. Vashan Wright is a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego. Though Wright’s data indicates significant amounts of water are trapped in rocks between 11:55 and 20 km (7:11–12:44 miles) below the surface, the surface of Mars is a desolate desert.
There’s a good chance that any life on Mars is underground.
Subsurface microbiologist Karen Lloyd of the University of Southern California in Los Angeles says, “If they are right, this is a game-changer.”. “.
The likelihood of subterranean life on Mars is increased by the presence of underground water. The last few decades have shown that the Earth’s interior conceals a massive biosphere. Now, it appears that Mars may experience the same thing. If life is present on Mars, it might be underground.
the biosphere at depth.
Biologists have been gathering evidence that life exists on Earth’s deep subsurface for more than thirty years. Through drilling deep into the sea floor and continents, scientists have discovered life hidden among layers and crystals of solid rock as well as in buried sediments.
Single-celled microorganisms, particularly bacteria and archaea, make up the majority of these dark dwellers. Existing for more than three billion years, these two enormous groupings predate both plants and animals as the most ancient known forms of life on Earth.
The deep biosphere’s extreme diversity has also come to light in the last 20 years. According to Cara Magnabosco, a geobiologist at ETH Zurich in Switzerland, “there’s actually quite a lot of different types of organisms living deep underground.”.
Phyla are the broad groupings of bacteria; out of an estimated 1,300 phyla, only a few dozen have been formally identified. As Magnabosco puts it, “you can find almost all of these phyla underground.”.
Not that they are dispersed equally, anyway. Two phyla, Firmicutes and Pseudomonadota, dominated the majority of ecosystems under land, according to a 2023 meta-analysis. Although much rarer, other types of bacteria included previously undiscovered phyla.
These microbes, unlike photosynthetic organisms at the surface, cannot directly obtain energy from sunlight because it is completely dark. The fact that they are mostly independent of the Sun is crucial to remember, according to Lloyd.
They are also not getting any additional inputs from above, like nutrients. Several of these deep ecosystems, according to Magnabosco, are “totally disconnected from the surface.”.
Chemosynthesis is the foundation of these ecosystems instead. The microorganisms obtain their energy through chemical reactions, whereby they absorb chemicals from the nearby rocks and water. For example, they might use gases as their source material, like hydrogen sulfide or methane. Chemical reactions occur below the surface in a plethora of diverse ways, according to Lloyd. A great deal of our time is devoted to discovering novel responses that sustain life. “.
Because chemosynthetic microbes are limited to the ocean’s depths and the solid subterranean, they may appear strange to us because they are uncommon in the sunny surface regions where we spend our lives. Nonetheless, they represent some of the planet’s oldest classes of living things. Chemosynthetic life is thought to have been the first on Earth according to certain theories regarding the origin of life.
It’s possible that Martian microorganisms are surviving on very little food, much like the slow microbes found deep beneath Earth’s oceans.
There are a few unusual animals in the subsurface, but single-celled microbes predominate. An investigation conducted in 2011 in South African mines found nematode worms in fracture water at a depth of 0:9–3:66 km (0:6-2:22 miles). It appears that the nematode population may be millennia old, as the water has been present for a minimum of 3,000 years. In fissure water located 1.4 km (0.9 mi) below the surface, a 2015 follow-up discovered flatworms, segmented worms, rotifers, and arthropods; the water there could have been as old as 12,300 years. A microscopic layer of bacteria on the rock’s surface provided food for the animals.
It appears to us that living far below ground would be very difficult. Although there is a lot of rock below the surface, the microbial populations are relatively small. By combining information on the quantity and variety of cells from drilling sites across the globe, Magnabosco and her colleagues calculated the size of the biomass that exists beneath continents in 2018. According to their estimation, beneath the continents of Earth, there exist between 2 and 6 × 10^29 cells. The observable universe contains only roughly 10^24 stars, in contrast.
According to Magnabosco, “we have a very numerically large number of cells beneath our feet.”. According to her, roughly 70% of all bacteria and archaea on Earth are found below the surface.
It’s still unclear how far down the biosphere goes. We don’t exactly know where the upper temperature limit of life is, but it probably exists. Though nothing can survive on the surface of molten lava, some microorganisms are surprisingly heat-tolerant. Methanopyrus kandleri, an archaean, is able to survive and proliferate at temperatures as high as 122C (252F).
If you go deep enough underground, pressure starts to become a problem too. Because it influences the kinds of chemical reactions that can take place and, consequently, the kinds of chemosynthetic microbes that can live there, the type of rock is also important. Lloyd says, “But we haven’t hit it yet; we just haven’t drilled that deep,” so he can’t give you an estimate of how far below the surface life is. The boundary might be unexpectedly deep: a 2017 study using material from a mud volcano revealed that life might be present 10 km (6 point 2 miles) below the surface of the ocean.
A portion of this life is spent moving incredibly slowly. According to Lloyd, “there are undoubtedly significant areas of the subsurface, mostly beneath our oceans, where nothing really happens for millions of years.”. The microbes in these environments have very little food because there is no way for them to escape and no fresh nutrients to enter from above. She explains, “That means they just don’t have the energy needed to form new cells.”. Rather, they are essentially in a state of stasis as their metabolism slows down. “It’s actually very plausible that a single cell could survive for thousands or even millions of years. ****.
This kind of life could feasibly be found in the water-rich rocks deep beneath Mars’ surface; it is dependent on chemical reactions between rocks and water and may have a very slow metabolic rate.
microbes on Mars.
Despite decades of unmanned missions to the red planet, there is still no conclusive or direct evidence of life on the planet. No living thing has ever ventured into the field of view of a Mars rover camera, and the surface is frigid and dry.
However, features like canyons provide compelling evidence that water was flowing on Mars’ surface billions of years ago. Wright’s team found that most of that water is underground, though some of it was likely lost to space.
For life as we know it, water is a necessary component, according to Lloyd. Possibly, only the subsurface of Mars is currently habitable, while the surface was once habitable. She states, “I’ve always liked the idea that life would be buried somehow.”.
Martian microorganisms might be surviving on very little food, much like the slow microbes found deep beneath Earth’s oceans. Magnabosco claims that “the same sort of processes that happen in our subsurface can happen on Mars.”.
Cara Magnabosco: There’s a good chance that life, if it ever developed there, is still there today.
The seasonal fluctuations in methane plumes in the Martian atmosphere are the most compelling proof of life as of yet. Methane is frequently produced by microorganisms on Earth, suggesting that the gas may be a waste product of subterranean life. Lloyd, though, advises caution. “There could be methane plumes for a variety of non-living reasons,” she states.
Life on Mars’ subsurface is also hampered by a plethora of additional factors. According to Lloyd, “life doesn’t just need water.”. It requires energy and a location, so a habitat is necessary. “Whether the pores in the Martian rock are big enough for microbes is still unknown. Similarly, since the deep rocks would be the source of chemical energy, their chemical composition is essential.
“Whether or not life emerged” is “the biggest uncertainty,” according to Magnabosco, regarding life on Mars. We are unable to determine whether conditions on Mars were ever favorable for the emergence of life since we do not know how the first living things originated from inanimate matter. She asserts, “Life has a very good chance of still surviving and being on Mars today if it was able to develop on the planet.”. “. .
Obviously, we should drill into Mars to find the Martian deep biosphere, but doing so would require drilling down to a depth of at least 10 km (6 point 2 miles), which is a significant lift even on Earth. “It’s much, much more difficult to do that on a planet without running water or breathable air,” claims Magnabosco.
Nonetheless, it ought to be feasible to accumulate the corroborating data. NASA’s proposed Mars Sample Return mission would return rocks from Mars to Earth, potentially containing signs of past life.
“It would be really beneficial to chase the methane,” remarks Lloyd. We don’t currently know the source of the gas. According to her, “it would be suggestive of life if we find that the water pockets are associated with the methane plumes.”.
Lastly, we could benefit from the presence of water on Mars if it is true. On Earth, subterranean water is brought to the surface by natural features like hot springs. According to Lloyd, “Mars has mud volcanoes.”. You can visit locations on Mars where deep subsurface samples that have been excavated and brought to the surface are actually present. ****.
Obtaining a conclusive response could take several decades. This may come as a disappointment, but Mars is far less active tectonically and hydrologically than Earth, indicating that life is either rare or nonexistent there. “Perhaps we are searching for life that has been extinct for a very long time,” adds Lloyd. In that case, instead of discovering living things, we might only discover fossil evidence. “In any case, it’s life on Mars,” she asserts.
The Genesis Quest: The geniuses and eccentrics on a quest to discover the origin of life on Earth is written by freelance science and environment journalist Michael Marshall.
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