Sedimentary, dear Johnson: Is NASA looking at the wrong rocks for clues to Martian life?

Sedimentary, dear Johnson: Is NASA looking at the wrong rocks for clues to Martian life?
ESEM image of a fossil fungal mycelium with associated 'cauliflower-like' microstromatolite formed by iron-oxidizing bacteria. From Koko Seamount, Pacific Ocean. 43 Ma old. Credit: Dr. Magnus Ivarsson

In 2020, NASA and European-Russian missions will look for evidence of past life on Mars. But while volcanic, igneous rock predominates on the Red Planet, virtually the entire Earth fossil record comes from sedimentary rocks.

Addressing the problem in Frontiers in Earth Science, Swedish scientists have begun compiling evidence of fossilized microbes in underexplored igneous environments on Earth, to help guide where to search for a Martian fossil record—and what to look for.

"We propose a 'volcanic microfossil atlas' to help select target sites for missions seeking evidence of extraterrestrial life, such as the NASA Mars mission 2020 and ExoMars," says lead author Dr. Magnus Ivarsson. "The atlas could also help us recognize what Mars microfossils might look like, by identifying biosignatures associated with different types of fossilized microbes."

Earth's deep biosphere

Ivarsson and colleagues study life buried in deep rock and deep time: fossilized remains of mysterious microbes, that have lived up to a kilometer below the deepest ocean floors for as long as 3.5 billion years.

"The majority of the microorganisms on Earth are believed to exist in the deep biosphere of the ocean and ," reveals Ivarsson. "Yet we are just now beginning to explore—through deep drilling projects—this hidden biosphere."

Sedimentary, dear Johnson: Is NASA looking at the wrong rocks for clues to Martian life?
Three-dimensional reconstruction made by synchrotron-based X-ray tomography (srxtm) of the same as in the image above. Fungal mycelium with microstromatolitic structures and remains of prokaryotic cell-like structures in between the fungal hyphae. Credit: Dr. Magnus Ivarsson

In a watery world that never sees sunlight, bacteria, fungi and other microbes have adapted to feed on the igneous rock that surrounds them—or even on each other. They spread through micro-fractures and cavities, forming complex and extended communities.

"Upon death, the microbial communities become fossilized on the walls of their rocky home. These microfossils can provide a history of microbial life in ."

A volcanic microfossil atlas

Crucially, Earth's oceanic crust is geochemically very similar to the volcanic rocks that dominate the Martian landscape.

"Our aim is to be able to use the oceanic crust microfossil record as a model system to guide Martian exploration," Ivarsson explains. "Our review of existing knowledge is an important first step, but a more comprehensive understanding of the deep life is needed to show where and what to search for."

To achieve this, says Ivarsson, we need to collect more data on microfossil appearance and location—but also, on their chemical composition.

Sedimentary, dear Johnson: Is NASA looking at the wrong rocks for clues to Martian life?
Three-dimensional reconstruction made by synchrotron-based X-ray tomography (srxtm) of a fossilized fungal mycelia and prokaryotic cell-like structures in between the hyphae forming a 'cob-web'. Part of the mycelium has chemically bored into a calcite crystal (seen in the lower part). Credit: Dr. Magnus Ivarsson

"These fossils often preserve immense morphological detail. For example, we can distinguish broad classes of fungi through the appearance of spores, fruiting bodies, mycelia and other growth states—or of bacteria, through the presence of cauliflower-like formations, generations of biofilms preserved as laminated sheets, and other characteristic community structures.

"But analysis of lipids and carbon isotopes in microfossils will make it possible to discriminate more precise groups based on their metabolism.

"Altogether this information will help to identify which types of microorganism are most likely to have been preserved on Mars, and which geochemical conditions most favour fossilization."

A fossil record on Mars

The microfossil atlas would therefore also help to determine which samples should be targeted for return to Earth, given the limited payload of the Mars missions.

"Both NASA's Mars 2020 and the ExoMars missions are capable of detecting larger fossilized structures from volcanic rocks, such as mm-sized mineralized fungal mycelia, or larger microstromatolites in open vesicles.

"ExoMars's 8 micrometer/pixel cameras have a greater chance of identifying small features and individual hyphae in situ on Mars. However, the NASA mission has the possibility of collecting samples for later investigation on Earth, and its 15 micrometer/px cameras may therefore be sufficient select samples with a high probability of containing biosignatures. These complimentary strategies increase the overall chance of detecting evidence of past life on Mars, if it exists," concludes Ivarsson.


Explore further

Microbes make tubular microtunnels on Earth and perhaps on Mars

More information: Magnus Ivarsson et al, Morphological Biosignatures in Volcanic Rocks – Applications for Life Detection on Mars, Frontiers in Earth Science (2019). DOI: 10.3389/feart.2019.00091
Provided by Frontiers
Citation: Sedimentary, dear Johnson: Is NASA looking at the wrong rocks for clues to Martian life? (2019, May 17) retrieved 24 May 2019 from https://phys.org/news/2019-05-sedimentary-dear-johnson-nasa-wrong.html
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May 18, 2019
I still say we should quit wasting time looking for life that might have lived millions of years ago and start putting life there. It's going to take a long time to make Mars even vaguely habitable and the sooner we start the sooner it will get done. If there was life still on there at least one of the rovers or other machines that have been put there would have had at least found some example or the waste result of life in the dirt. From what I've read so far we haven't found a single thing that indicates that anything is living there now or has been in the past. The only things we have found indicate there was once a lot more water on the planet than it has now. Maybe the majority of the water was gone before life ever had a chance to even get started by whatever means it generally starts with. We don't even know how life got started on this planet. There are a whole lot of theories about various
possibilities but we still don't know for sure if any of them are correct.

May 18, 2019
we should quit wasting time looking for life that might have lived millions of years ago and start putting life there.


Science is never a waste of time, see its return on investment (say, laptops and internet to write here), and we can do both simultaneously.

Besides that, this is an age old open question that many want answered anyway.

We don't even know how life got started on this planet. There are a whole lot of theories about various possibilities but we still don't know for sure if any of them are correct.


We have a most likely candidate based on observation, evolution from alkaline hydrothermal vents [ https://www.natur...l2016116 ]. Life evolved rapidly here [ https://www.natur...8-0644-x ] and the same circumstances were coincident on Mars a billion years later - if not before (global ocean; Spirit found alkaline hydrothermal vents).

ExoMars is to drill into the crust because extant or extinct life may be there.

May 19, 2019
I still say we should quit wasting time looking for life that might have lived millions of years ago and start putting life there
We NEED to know if it's already inhabited. And I agree, finding more recent evidence in sedimentary rock near the surface makes more sense than old life living deep underground.
It's going to take a long time to make Mars even vaguely habitable and the sooner we start the sooner it will get done
Its already habitable. Underground. We can create cubic miles of pressurized, conditioned space with existing tech.

And by the time humans are able to terraform planets, the millions of martians living quite comfortably in their subterranean cities are not going to want to screw up the surface with muck and bugs and fungus. Machines love mars BECAUSE it's not terraformed. They'll be doing all the necessary work on the surface. Martians will be quite content in their bubbles and voids and tunnels and reservoirs, all safely isolated from each other.

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